Table 2.

Characteristics of included studies [ordered by study ID]

Adib-Hajbaghery 2013
Methods	Parallel-group, blinded randomized trial, conducted in Iran. Study dates not reported
Participants	88 people aged 15 – 70 years undergoing appendectomy under general anaesthesia. Exclusion: past history of nausea and vomiting in the past 24 h, prior use of acupressure or acupuncture, history of gastrointestinal or ear disorders, neurological impairment, fever, unanticipated perioperative complications
Interventions	Acupressure wristband placed at P6 points on both wrists, applied in the recovery room when participant was awake and removed after 7 hours following surgery (n = 44) Sham group was acupressure wristbands without bead on P6 points applied to both wrists, applied in the recovery room when participant was awake and removed after 7 hours following surgery (n = 44)
Outcomes	Nausea (0 – 7 h), vomiting (0 – 7 h), risk of rescue antiemetic (metoclopramide 10 mg)
Notes	No power calculation done. Funding sources not declared. Authors declare no conflict of interest in the study
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants were “randomly allocated to two groups using a dice (odd numbers to the acupressure group and even numbers to the control group.”
Allocation concealment (selection bias)	Unclear risk	Insuffient information.
Blinding of patients (performance bias) All outcomes	Low risk	Participants blinded to intervention.
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“Staff blinded to grouping”.
Blinding of outcome assessor (detection bias) All outcomes	High risk	Researcher and nurse likely to know allocation group.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient information.
Selective reporting (reporting bias)	High risk	Participant discomfort with wristbands monitored by researchers every 2 hours but not reported
Other bias	Low risk	Baseline characteristics for age, body mass index, duration of anaesthesia and incision length were comparable
Agarwal 2000
Methods	Parallel-group randomized trial, conducted in India. Study dates not reported
Participants	200 people undergoing endoscopic urological surgery. Exclusion: patient refusal to participate in study, previous history of PONV and motion sickness, impaired renal function with increased urea and creatinine concentrations, diabetes mellitus, obesity, patients receiving antiemetic medication, histamine H2 receptor antagonist within 72 hours of surgery. No participant withdrew from the study.
Interventions	Acupressure wristband placed at P6 points on both forearms, applied 30 min before induction of anaesthesia and removed after 6 hours following surgery (n = 100) Sham group was the spherical bead of acupressure wristbands placed on posterior surface, applied 30 min before induction of anaesthesia and removed 6 hours after surgery (n = 100)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), side effects of acupressure, risk of rescue antiemetic drug
Notes	Rescue antiemetic was ondansetron 4 mg IV. No side effects or complications noted in either group. No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Patients were assigned to two different groups according to a computer-generated table of random numbers”
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“An anesthesiologist blinded to the therapy registered the incidence of nausea and vomiting at three different times in the first 24 hr postoperatively: on arrival of the patient in PACU, and at six hours (time of removal of acupressure wristband) and 24 hr after operation”
Incomplete outcome data (attrition bias) All outcomes	Low risk	“No patient was excluded after admission to the study”.
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable: “Patients were comparable in both the groups as regards to age, sex, height and weight”
Agarwal 2002
Methods	Parallel-group randomized trial, conducted in India. Study dates not reported
Participants	150 adults undergoing laparoscopic cholecystectomy. Exclusion: patient refusal to participate in study, previous history of PONV and motion sickness, impaired renal function with increased urea and creatinine concentrations, diabetes mellitus, obesity, patients receiving antiemetic medication, histamine H2 receptor antagonist within 72 hours of surgery
Interventions	Acupressure wristband placed at P6 points on both forearms, applied 30 min before induction of anaesthesia and removed after 6 hours following surgery (plus normal saline 1 mL IV just before induction of anaesthesia) (n = 50) Sham group was the spherical bead of acupressure wristbands placed on posterior surface, applied 30 min before induction of anaesthesia and removed 6 hours after surgery (plus normal saline 1 mL IV just before induction of anaesthesia) (n = 50) Antiemetic group was ondansetron 4 mg IV just before induction of anaesthesia (plus sham treatment outlined above) (n = 50)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), risk of rescue antiemetic drug
Notes	Rescue antiemetic was ondansetron 4 mg IV if participant vomited more than once. No side effects or complications noted in any of the groups. Data for outcome (0 – 24 h) obtained by correspondence with author. No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Patients were randomised into three groups of 50 each using a table of random numbers..”
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The incidence of PONV was evaluated by a blinded observer”.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for 150 patients randomized.
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable: “Patients were comparable in both the groups as regards to age, sex, height, weight and duration of surgery”
Alkaissi 1999
Methods	Parallel-group randomized trial, conducted in Sweden. Study dates not reported
Participants	60 women undergoing day-case minor gynaecological surgery. Exclusion: patients undergoing local anaesthesia and those given prophylactic antiemetic during anaesthesia (n = 10, replaced by randomizing another 10 participants at the end of the study)
Interventions	Acupressure wristband placed at P6 point on both forearms. Applied before surgery and left on for 24 hours. Draped with a dressing during the stay in the hospital (n = 20) Sham acupressure applied to dorsal side of forearms. Applied before surgery and left on for 24 hours. Draped with a dressing during the stay in the hospital (n = 20) Reference group were informed and anaesthetized in the same way as the other 2 groups (n = 20)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), risk of rescue antiemetic drugs
Notes	Rescue antiemetics were metoclopramide 10 mg IV at participant’s request; if not effective, then given droperidol 1.25 mg IV. Reference group received no treatment and were not included in data analysis. No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“The nurses who asked the patients about nausea, and administered antiemetics on the postoperative ward were not aware of which treatment the patient received or where the PC6 acupoint is located”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The nurses who asked the patients about nausea, and administered antiemetics on the postoperative ward were not aware of which treatment the patient received or where the PC6 acupoint is located”. These nurses also noted vomiting episodes
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons were given for 10 dropouts, who were replaced by randomising another 10 participants at the end of the study. “The dropouts were evenly distributed between the groups.” No missing data reported for 60 participants analysed
Selective reporting (reporting bias)	High risk	Primary outcome (PONV) reported. Description of side effects not given
Other bias	Low risk	Demographic data appeared to be comparable.
Alkaissi 2002
Methods	Parallel-group randomized trial, conducted in Sweden. Study dates not reported
Participants	410 women undergoing elective gynaecological surgery. No exclusion criteria specified. 30 participants were withdrawn because they were: given local anaesthesia (n = 12), or an antiemetic was given without the criteria for treatment of PONV being met (n = 14), malignant hyperthermia (n = 1), allergy to latex (n = 2), and could not read Swedish (n = 1). These 30 participants were replaced by another 30 at the end of the study period
Interventions	Acupressure wristband placed on P6 point on both forearms just before start of anaesthesia, left on for 24 h (n = 135) Sham group included acupressure wristbands at non-acupoint on both forearms just before start of anaesthesia, left on for 24 h (n = 139) Reference group received no prophylactic treatment and was not blinded (n = 136)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), side effects of acupressure, risk of rescue antiemetic (type of drug not described)
Notes	Reference group received no treatment and were not included in data analysis. Adverse effects: wristbands felt uncomfortable, produced red indentation, or caused itching, headache and dizziness, or wrists hurt and tightness of wristband caused swelling or deep marks or blistering at site of stud Financial support was provided by the County Council of Östergötland (Project F98–305) Sweden. No details about any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	“The wrists were wrapped for blinding”. Participants reported outcomes
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The wrists were wrapped for blinding”. Participants reported outcomes
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons were given for 30 dropouts, who were replaced by randomising another 30 participants at the end of the study. “Withdrawals were evenly distributed between the groups.” No missing data reported for 410 participants analysed
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Demographic data appeared to be comparable in Table 2.
Allen 1994
Methods	Parallel-group randomized trial, conducted in England. Study dates not reported
Participants	46 women undergoing gynaecological surgery. Exclusions: previous exposure to elasticized wristbands for the prevention of motion sickness
Interventions	Acupressure wristband placed on P6 point of dominant arm before premedication (90 min before surgery) (n = 23). Duration of treatment not given Sham acupressure wristband placed on dorsum of dominant wrist before premedication (n = 23). Duration of treatment not given
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h).
Notes	Rescue antiemetic was prochlorperazine 12.5 mg IM 4-hourly when necessary. More than 1 dose of prochlorperazine data given (not included in data analysis). No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar in participants with no previous experience with this form of acupressure
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Unclear risk	Insufficient information.
Incomplete outcome data (attrition bias) All outcomes	Low risk	“No patient refused to participate in the study, nor were there any withdrawals”
Selective reporting (reporting bias)	High risk	Risk of rescue antiemetic drug (1 or more doses) was not given in the results. Description of side effects not reported
Other bias	Low risk	Baseline characteristics were comparable. “The ages and weights of the patients in the two groups were comparable..”
Amir 2007
Methods	Parallel-group randomized trial, conducted in India. Study dates not reported
Participants	40 children and adults undergoing middle ear surgery. Exclusion: People with cardiovascular disease, central nervous system problems, previous history of PONV and/or motion sickness, and smokers. No details about withdrawals or loss to follow-up
Interventions	Group 1: electro-acupuncture at frequency of 4 Hz and current intensity increased to a degree just less than what caused discomfort, given 20 min before induction for duration of surgery (n = 20) Group 2: sham electro-acupuncture. No details given except that participants experienced needle pricks (n = 20)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), risk of rescue antiemetic drug (0 – 24 h), risk of adverse effects
Notes	Rescue antiemetic was ondansetron 4 mg IV after first episode of PONV and repeated when necessary at 6-hourly intervals. No side effects in sham electro-acupuncture group. Erythema occurred in 3 participants in the electro-acupuncture group No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Informed consent was taken from the selected patients and they were divided into two groups of twenty each using a computer-generated table of random numbers”
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“A blinded observed collected postoperative data of PONV”.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for the 20 participants randomized to each group
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “Differences in mean age, weight, sex and duration of surgery were statistically insignificant”
Andrzejowski 1996
Methods	Parallel-group randomized trial, conducted in United Kingdom. Study dates not reported
Participants	36 women undergoing total abdominal hysterectomy. Exclusions: metal or elastoplast allergy, anticoagulant therapy, local skin disease at P6 acupoint or sham point, or chronic treatment with antiemetics
Interventions	Semipermanent acupuncture needle inserted at P6 acupoint on both wrists 20 min before induction, left in place until second postoperative day (n = 18) Sham semipermanent acupuncture needle inserted in sham point 20 min before induction, left in place until second postoperative day (n = 18)
Outcomes	Nausea (0 – 8 h), vomiting (0 – 8 h), risk of antiemetic rescue drug, side effects
Notes	Antiemetic rescue was prochlorperazine 12.5 mg IM when necessary. No side effects reported with interventions. No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information. “Patients were allocated randomly into one of two groups”
Allocation concealment (selection bias)	Unclear risk	Insufficient information. “This was achieved by concealing the assignment schedule in sealed envelopes which were opened by the investigator just before inserting the needles”. Comment: not sure if envelopes were sequentially numbered and opaque
Blinding of patients (performance bias) All outcomes	Low risk	Assessments were made by the participants, who were blinded to their treatment
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	Assessments were made by the participants, who were blinded to their treatment
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for 36 participants randomized.
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “There was no significant difference between the two groups in age, weight, total morphine consumed, or duration of anaesthesia”
Arnberger 2007
Methods	Parallel-group randomized trial, conducted in Switzerland and Austria. Study dates not reported
Participants	220 women undergoing elective gynaecological and abdominal laparoscopic surgery of more than 1 hour duration. Exclusion: pregnant and breast-feeding women, and women with eating disorders, obesity (BMI > 35kg/m2), severe renal or liver impairment, central nervous system injury, vertebrobasilar artery insufficiency, vestibular disease, cytostatic therapy, and preoperative vomiting or antiemetic therapy. No participant withdrew from study
Interventions	P6 group: during anaesthesia, neuromuscular blockade was monitored by a conventional nerve stimulator at a frequency of 1 Hz over the median nerve (first electrode 1 cm proximal to P6 acupoint and second electrode placed 2 cm distal to the P6 acupoint) on the dominant hand (n = 110) Sham group: during anaesthesia, neuromuscular blockade was monitored by a conventional nerve stimulator at a frequency of 1 Hz over the ulnar nerve (first electrode 1 cm proximal to the point at which the proximal flexion crease of the wrist crosses the radial side of the tendon to the flexor carpi ulnaris muscle at the volar side of the wrist and second electrode placed 3 cm proximal to the distal electrode) on the dominant hand (n = 110)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), risk of rescue antiemetic drug (0 – 24 h), risk of adverse effects
Notes	Rescue antiemetic was ondansetron 4 mg IV if 2 or more episodes of vomiting or persistent nausea; with repetition after 2 hours. No local irritation, redness, contact dermatitis or muscle ache (side effects) were recorded. Nausea (0 – 6 h), vomiting (0 – 6 h), and incidence of rescue antiemetic (0 – 6 h) also reported Support was provided solely from institutional sources. Authors declared no conflict of interests
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“After induction of anaesthesia, patients were assigned to one of two groups using a set of computer-generated random numbers”
Allocation concealment (selection bias)	Low risk	“The assignments were kept in sealed, sequentially numbered envelopes until used, and the envelope numbers with the assignment were recorded”
Blinding of patients (performance bias) All outcomes	Low risk	“Patients and PONV evaluators were not informed of the group assignments”
Blinding of healthcare providers (performance bias) All outcomes	High risk	“The attending anaesthesiologist could not be blinded to the group assignment, but he or she was not involved with the PONV assessment”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Patients and PONV evaluators were not informed of the group assignments”
Incomplete outcome data (attrition bias) All outcomes	Low risk	“Two hundred twenty patients were recruited for this study without any dropout over the observation period”
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “Demographic and morphometric characteristics and factors likely to influence PONV were similar in the two groups”
Barsoum 1990
Methods	Parallel-group randomized trial, conducted in England. Study dates not reported
Participants	162 people undergoing general surgery. 10 participants withdrew because of language or age difficulty with completing analogue score, premature removal of wristbands, and incomplete follow-up data
Interventions	Acupressure wristbands placed on P6 acupoint of both wrists in the recovery room (n = 49) Sham acupressure wristbands (no studs) were applied to both wrists in the recovery room and antiemetics given only if clinically required (n = 54) Antiemetic group was given prochlorperazine 12.5 mg IM with each postoperative opiate injection and when clinically required, and wore an acupressure band without stud on both wrists in the recovery room (n = 49)
Outcomes	Vomiting (0 – 24 h), risk of rescue antiemetic (prochlorperazine)
Notes	Nausea scores were reported for those participants who could not eat. Number of participants who were free of nausea was not given. Vomiting on postoperative day 2 and 3 also reported. 4 participants reported some local tightness and discomfort (1 of these experienced carpal tunnel-like symptoms) No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar and all participants were told that they were wearing wristbands to try to prevent PONV
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Unclear risk	Insufficient information.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons for withdrawals were given. No missing data reported for the 152 participants analysed
Selective reporting (reporting bias)	High risk	Severity of nausea was reported but risk of nausea was not.
Other bias	Low risk	Baseline characteristics appeared to be comparable. “It can be seen that the groups were comparable with regard to the range of operation and anaesthetic agents used”
Butkovic 2005
Methods	Parallel-group randomized trial, conducted in Croatia. Study dates not reported
Participants	120 children (5 – 14 years) undergoing hernia repair, circumcision, or orchidopexy. Exclusion: children predisposed to nausea and vomiting secondary to gastroesophageal reflux, motion sickness, and inner ear or central nervious system disorders
Interventions	Group 1: laser acupuncture on P6 acupoint bilaterally for 1 min, 15 min before induction of anaesthesia and IV infusion of saline (n = 40) Group 2: metoclopramide 0.15 mg/kg IV and sham laser on P6 acupoint bilaterally for 1 min, 15 min before induction of anaesthesia (n = 40) Group 3: sham laser stimulation on P6 acupoint bilaterally for 1 min, 15 min before induction of anaesthesia and saline infusion (n = 40)
Outcomes	Vomiting (0 – 2 h), risk of rescue antiemetic drug.
Notes	Rescue antiemetic was ondansetron 0.1 mg/kg IV if vomiting was severe. No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make intervention appear similar
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“Researchers were double-blinded” but no specific details about how blinding was achieved. Comment: probably done
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Researchers were double-blinded” but no specific details about how blinding was achieved. Comment: probably done
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for the 120 children analysed.
Selective reporting (reporting bias)	High risk	Description of side effects not included. Nausea not reported because it may be difficult to assess in children
Other bias	Low risk	Baseline characteristics were comparable. “Demographic data showed no significant difference among groups”
Direkvand-Moghadam 2013
Methods	Parallel 3-arm randomized trial, conducted in Iran. Study conducted from September 2011 to October 2012
Participants	102 healthy women, aged 18 – 35 years, at first to fourth pregnancy, with normal foetal heart rates, undergoing Caesaren delivery with spinal anaesthesia between 29 September 2011 to 23 October 2012 at University Hospital of Ilam, West of Iran. Exclusion: Acute or chronic diseases associated with nausea and vomiting, carpal tunnel syndrome, preoperative opioids, weights < 50 kg or > 100 kg
Interventions	Group 1: No P6 treatment group (n = 34) Group 2: Metoclopramide IV before spinal anaesthesia induction (n = 34) Group 3: P6 acupressure wristbands applied to both wrists 15 min before spinal anaesthesia induction and removed 6 hours after surgery (n = 34)
Outcomes	Nausea (0 – 6 h), vomiting (0 – 6 h), risk of rescue antiemetic drugs (0 – 6 h)
Notes	All treatment groups were used in the analysis. Details of exact type of rescue antiemetic were not given. Power calculation done. Funding from Ilam University of Medical Sciences. No financial or other competing interests declared by authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Patients were randomly assigned to one of the three groups by a trained midwife, with 34 cases in each group, at the obstetrical triage unit, by using a random number chart”
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Unclear risk	Insufficent information.
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“The researcher was not aware of grouping of participants”.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The data collection was carried out by a trained midwife who was not also aware of each medication and who had no idea about the plan of the study. ”
Incomplete outcome data (attrition bias) All outcomes	Low risk	“None of the 102 enrolled parturients were withdrawn for any reason”
Selective reporting (reporting bias)	High risk	Description of side-effects of acupressure or metoclopramide were not reported
Other bias	Low risk	Baseline characteristics (age, weight, height, gestational age, duration of surgery” were comparable
Duggal 1998
Methods	Parallel-group randomized trial, conducted in Canada. Study dates not reported
Participants	263 women undergoing spinal anaesthesia for elective Caesarean delivery. Excluded: women with a history of hyperemesis gravidarum or if they had received antiemetic medication during the 48 h before surgery. 8 women excluded for failing to wear wristbands for 10 hours, 3 had received prophylactic antiemetics, and 8 were not given standard combination of intrathecal drugs (total 19 withdrawals)
Interventions	Acupressure wristbands were applied to both wrists just before induction of spinal anaesthesia and worn for 10 hours (n = 122) Sham acupressure wristbands were applied at P6 acupoint (but stud missing) on both wrists just before induction of spinal anaesthesia and worn for 10 hours (n = 122)
Outcomes	Nausea (0 – 10 h), vomiting (0 – 10 h), risk of rescue antiemetic (type of drug not given), side effects of acupressure. Patients recorded outcome measures on a questionnaire
Notes	Adverse effects of acupressure wristbands: tightness, swollen hands, problems with infusion, itching wrists. Intraoperative nausea and vomiting reported Funding by a grant from the BC Medical Services Foundation. Wristbands were donated by Sea Band UK Ltd. No details of any declarations of interest among the authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“A table of random numbers was used to allocate patients to one of two groups”
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	“The nature of the bands was therefore unknown to the patient, anaesthetist and investigators for the duration of the study”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“The nature of the bands was therefore unknown to the patient, anaesthetist and investigators for the duration of the study”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The nature of the bands was therefore unknown to the patient, anaesthetist and investigators for the duration of the study”
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons for withdrawals were given. No missing data reported for the 244 participants analysed
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “Demographic analysis revealed no statistically significant difference between subjects in the two groups”
Dundee 1986
Methods	Parallel-group randomized trial, conducted in Ireland. Study dates not reported
Participants	75 women undergoing minor gynaecological surgery.
Interventions	Group 1: acupuncture at P6 acupoint with 5 min manual stimulation (1.2 cm 30 gauge needle) after premedication with nalbuphine 10 mg (n = 25) Group 2: sham acupuncture at a dummy point on lateral elbow crease with 5 min manual stimulation (1.2 cm 30 gauge needle) after premedication with nalbuphine 10 mg (n = 25) Group 3: no further treatment after premedication with nalbuphine 10 mg (n = 25)
Outcomes	Nausea (0 – 6 h), vomiting (0 – 6 h), side effects of treatment
Notes	No side effects noted in either group. Group 3 data were excluded from data analysis. Presence or absence of needle marks and its location may have been observed by the outcome assessor No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	The authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Their assessments were performed by an observer who was unaware of which patients had undergone acupuncture”
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for 75 participants analysed.
Selective reporting (reporting bias)	Unclear risk	No details about the use of rescue antiemetic in anaesthetic protocol. The risk of rescue antiemetic drug not reported
Other bias	Low risk	“The groups were comparable in average age, weight, and duration of anaesthesia”
Dundee 1989
Methods	Parallel-group randomized trial, conducted in Ireland. Study dates not reported
Participants	155 women undergoing minor gynaecological surgery.
Interventions	Acupuncture at P6 acupoint with 5 min manual stimulation after premedication (n = 31) Electroacupuncture at P6 acupoint for 5 min after premedication (n = 31) Antiemetic group 1 had cyclizine 50 mg IM after premedication (n = 31) Antiemetic group 2 had metoclopramide 10 mg IM after premedication (n = 31) Reference group had no treatment (n = 31).
Outcomes	Nausea (0 – 6 h), vomiting (0 – 6 h), side effects of treatment
Notes	For data analysis purposes, manual acupuncture and electro-acupuncture were combined. Reference group received no treatment and were not included in data analysis. This paper reported both controlled and uncontrolled studies of P6 stimulation. Used original data from secondary papers related to this study (Dundee 1989) (note that metoclopramide group was not included in this trial, but the results of other groups are the same). According to the authors, there were no side effects associated with acupuncture groups but some participants complained of drowsiness following antiemetic drug administration. For data analyses, manual acupuncture group was compared with cyclizine, and electroacupuncture group was compared with metoclopramide No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Patients were visited at 1 h and 6 h after operation by a person who was unaware of the preoperative treatment”
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for 155 participants analysed.
Selective reporting (reporting bias)	Unclear risk	No details about the use of rescue antiemetic in anaesthetic protocol. The risk of rescue antiemetic drug not reported
Other bias	Unclear risk	Demographic comparisons between groups were not given.
Ebrahim Soltani 2010
Methods	Parallel 4-group randomized trial, conducted in Iran. Study conducted in Iran during 2007 to 2008
Participants	200 participants aged 10 – 60 years old, with ASA physical status I to II, undergoing strabismus surgery. Exclusion criteria: nausea or vomiting within 1 week of surgery, local infection near acupoint, symptomatic comorbidities, travel sickness, length of stay in the recovery room more than 2 hours or those receiving any medical therapy before surgery
Interventions	Group 1: sham acupressure wristbands place inappropriately on the posterior surface of both forearms 30 min before induction of anaesthesia plus saline 1ml IV. Removed wristband 6 hours after surgery (n = 50) Group 2: sham acupressure wristbands place inappropriately on the posterior surface of both forearms 30 min before induction of anaesthesia plus metoclopramide 0.2 mg/kg IV immediately before induction. Removed wristband 6 hours after surgery (n = 50) Group 3: sham acupressure wristbands place inappropriately on the posterior surface of both forearms 30 min before induction of anaesthesia plus ondansetron 0.15 mg/kg IV immediately before induction. Removed wristband 6 hours after surgery (n = 50) Group 4: bilateral wristbands on P6 acupoint 30 min before induction of anaesthesia plus saline 1ml IV. Removed wristband 6 hours after surgery (n = 50)
Outcomes	Nausea (0 – 2 h), Vomiting (0 – 2 h) in recovery room
Notes	Subgroup analysis for adults and children not done as overall population was mixed in age range (10 – 60 years). No incidence for postoperative nausea or vomiting (0 – 24 h) reported No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient details. “Patients were randomised into four groups using random numbers, with 50 cases in each group.”
Allocation concealment (selection bias)	Unclear risk	Insufficient details.
Blinding of patients (performance bias) All outcomes	Low risk	Authors attempted to blind antiemetic drugs use with saline placebo and used sham acupressure wristbands on non-acupoint
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Wristbands were not covered with dressing. No details about whether healthcare providers were blinded or not
Blinding of outcome assessor (detection bias) All outcomes	Low risk	Nursing staff recording the PONV were unaware of group allocations
Incomplete outcome data (attrition bias) All outcomes	Low risk	“No patient was excluded after admission to the study.”
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	“There was no statistically significant differences with respect to demographic data between groups in the study.”
El-Deeb 2011
Methods	Parallel 3-group randomized trial, conducted in Egypt. Study dates not reported
Participants	450 women undergoing elective Caesaren delivery using spinal anaesthesia. Exclusion criteria: previous acupuncture treatment in the last 6 months, nausea or vomiting during 24 h preoperatively, diabetes, hypertension, cardiovascular disease, and any other major systemic comorbidities
Interventions	Group 1: sham group (normal saline IV and sham electroacupuncture at dorsal side of forearm for 30 minutes) before spinal anaesthesia (n = 150) Group 2: ondansetron group (4 mg ondansetron IV 30 minutes and sham electroacupuncture at dorsal side of forearm for 30 minutes before spinal anaesthesia (n = 150) Group 3: electroacupuncture group (normal saline IV and electroacupuncture at P6 acupoint on both wrists for 30 minutes before spinal anaesthesia (n = 150)
Outcomes	Postoperative nausea (0 – 6 h), postoperative vomiting (0 – 6 h), rescue antiemetic (ondansetron 4 mg IV, 0 – 6 h), treatment side effects
Notes	“No local (cutaneous) side effects were reported at the acu-stimulation site by any patient in the treatment groups during the 24h study period. No complications were noted” No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient details given.
Allocation concealment (selection bias)	Unclear risk	Sealed envelop used. Comment: not sure if envelopes were sequentially numbered and opaque
Blinding of patients (performance bias) All outcomes	Low risk	Authors applied placebo drug and sham electroacupuncture techniques but blinding of participants not specified
Blinding of healthcare providers (performance bias) All outcomes	Low risk	Authors applied placebo drug and sham electroacupuncture techniques but blinding of healthcare providers not specified
Blinding of outcome assessor (detection bias) All outcomes	Low risk	Outcomes assessed by “independent anaesthetist who was blinded to group assignment”
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for 450 participants analysed.
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	“The three groups were not significantly different with respect to demographic characteristics, intraoperative ephedrine dose, gestational age, and duration of surgery”
Ertas 2015
Methods	Parallel-group double-blinded randomized trial, conducted in Turkey. Study dates not reported
Participants	62 adult women undergoing gynaecological laparoscopy under general anaesthesia. Exclusion: women who had nausea and vomiting within 24 h before surgery, use of antiemetics or glucocorticoids within 24 hours before surgery, users of pacemakers, pregnant or nursing women, obese women, diseases associated with nausea and vomiting, those switched from laparoscopic to laparotomy
Interventions	Group 1: ReliefBand applied 15 – 30 min, at 31 Hz, on dominant hand before the operation and activated for 24 hours after surgery (n = 31) Group 2: Sham ReliefBand (electrodes wrapped in a plastic bandage and inactivated) applied 15 – 30 min, at 31 Hz, on dominant hand before the operation for 24 hours after surgery (n = 31)
Outcomes	Risk of rescue antiemetic (IV metoclopramide 0.5 mg/kg) drug (0 – 24 h) and adverse effects of device. No incidence of postoperative nausea or vomiting reported in the first 24 h after surgery
Notes	Severity of postoperative nausea and vomiting data not used. Authors stated that no adverse effects related to ReliefBand were observed. Power calculation done. Authors declared no financial or conflict of interest. Details about funding support not given
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Random numbers displayed on a list of codes prepared by a computerized system.”
Allocation concealment (selection bias)	Low risk	“These codes were written on paper slips, which were placed in numbered opaque sealed envelopes.”
Blinding of patients (performance bias) All outcomes	Low risk	“The patient and the research worker who held the records of the patient had no idea whether the ReliefBand was an authentic or a sham device.”
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The patient and the research worker who held the records of the patient had no idea whether the ReliefBand was an authentic or a sham device.”
Incomplete outcome data (attrition bias) All outcomes	Low risk	All 62 women followed up.
Selective reporting (reporting bias)	High risk	Incidence of postoperative nausea and vomiting (0 – 24 h) not reported
Other bias	Low risk	Baseline characteristics (age, height, body weight, duration of anaesthesia, duration of surgery, Apfel risk scores, smoking history, history of PONV) were comparable between groups
Fassoulaki 1993
Methods	Parallel-group randomized trial, conducted in Greece. Study dates not reported
Participants	106 women undergoing abdominal hysterectomy. Exclusions: 3 women in the sham group were excluded because they were given metoclopramide in the postoperative period for persistent vomiting (but these data were included for risk of rescue antiemetic given analysis)
Interventions	Transcutaneous electrical nerve stimulation on the P6 acupoint was applied 30 – 45 min before induction and continued for 6 hours postoperatively (n = 51) Sham group was treated the same way but with the electrical stimulator turned off (n = 52)
Outcomes	Vomiting (0 – 2 h) without antiemetic rescue, risk of rescue antiemetic (metoclopramide)
Notes	Potential bias if outcome assessor removed plastic bag covering the stimulator. Reported vomiting 2 – 4 h, 4 – 6 h, 6 – 8 h intervals. No data on vomiting (0 – 8 h) No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	“The stimulator, active or inactive, was covered with dark plastic bags, not allowing distinction between active and inactive stimulators”
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	Vomiting was assessed by “an independent observer who was unaware of the patient randomization and of TENS treatment”
Incomplete outcome data (attrition bias) All outcomes	High risk	“Three patients, originally assigned to the control groups, who received postoperatively metoclopramide because of persistent vomiting were eliminated from further vomiting evaluation and consequently from the study”. Comment: may introduce clinically relevant bias in summary effect measure
Selective reporting (reporting bias)	High risk	Nausea and side effects were not reported.
Other bias	Low risk	Baseline characteristics were comparable. “The two groups did not differ in age, body weight, duration of anaesthesia, and duration of surgery”
Ferrara-Love 1996
Methods	Parallel-group randomized trial, conducted in United States. Study dates not reported
Participants	136 adults undergoing orthopaedic, general, plastic, and ‘other’ surgery. Exclusions: 46 participants excluded after randomisation for failure to meet inclusion criteria
Interventions	Group 1: acupressure wristbands placed on P6 acupoint during surgery until hospital discharge (n = 30) Group 2: sham acupressure wristbands without studs placed on P6 acupoint during surgery until hospital discharge (n = 30) Group 3: reference group had no acupressure treatment (n = 30)
Outcomes	Nausea in the operating room after surgery, risk of rescue antiemetic drugs in the operating room if nausea persisted and/or emesis occurred
Notes	No treatment group excluded from data analysis. No cumulative outcome data Study was funded by grants from the American Society of PostAnesthesia Nurses and SeaBand, United Kingdom No details about any declarations of interest among authors.
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	High risk	“Randomization was done by birth date with even numbered months and days assigned to the treatment group, odd months and days assigned to the placebo group and combinations of even/odd months and days assigned to the control group”
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Low risk	PACU staff were blinded.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Incidence of postoperative nausea and vomiting was documented by the PACU staff who were blinded as to treatment and placebo group”
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for the 90 participants analysed.
Selective reporting (reporting bias)	High risk	Risk of vomiting and side effects were not reported in the results
Other bias	Low risk	Baseline characteristics were comparable. “There were no differences between groups in demographic and perioperative variables” as tested using appropriate univariate statistical tests
Frey 2009a
Methods	Parallel 4-arm randomized trial, conducted at a single German centre. Study dates not reported
Participants	214 adult women undergoing vaginal hysterectomy requiring general anaesthesia. Exclusion: women with cardiac pacemaker or implanted defibrillator, at risk of malignant hyperthermia, had allergy to nickel/chrome, or change in surgical technique
Interventions	Group 1: Acu-stimulation (ReliefBand) before induction of anaesthesia at P6 acupoint on dominant forearm for 24 h after surgery (n = 48) Group 2: Acu-stimulation (ReliefBand) after induction of anaesthesia at P6 acupoint on dominant forearm for 24 h after surgery (n = 53) Group 3: Sham acustimulation (inactivated ReliefBand electrodes with a silicone cover) before induction of anaesthesia at P6 acupoint on dominant forearm for 24 h after surgery (n = 49) Group 4: Sham acustimulation (inactivated ReliefBand electrodes with a silicone cover) after induction of anaesthesia at P6 acupoint on dominant forearm for 24 h after surgery (n = 50)
Outcomes	Nausea (0 – 6 h), vomiting (0 – 6 h), rescue antiemetic (tropisetron 2 mg)
Notes	Combined Groups 1 and 2 as acustimulation group, and Groups 3 and 4 as sham group for analysis. No cumulative incidence of 0 – 24 h outcomes reported No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient details.
Allocation concealment (selection bias)	Unclear risk	Participants randomized by “drawing a sealed envelope indicating treatment assignment.” No details about envelopes being opaque
Blinding of patients (performance bias) All outcomes	Low risk	Authors made efforts to inactivate electrodes and place a silicone cover over the device which “was invisible for both patients and investigators.”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	Authors made efforts to inactivate electrodes and place a silicone cover over the device which “was invisible for both patients and investigators.”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The investigators responsible for collecting data were blind to the treatments administered to the study patients.”
Incomplete outcome data (attrition bias) All outcomes	Low risk	14 participants excluded after randomization due to change in surgical technique, resulting in final sample size of 200
Selective reporting (reporting bias)	High risk	Side effects of active and sham ReliefBand not assessed or reported
Other bias	Low risk	Groups were comparable for participant characteristics, duration of surgery and anaesthesia and risk score for PONV
Frey 2009b
Methods	Parallel 4-arm randomized trial (single centre) conducted in Germany. Study dates not reported
Participants	229 patients, aged more than 18 years with ASA physical status I to III, undergoing laparoscopic cholecystectomy. Exclusion criteria were patients with cardiac pacemaker or implanted cardioverter/defibrillator, at risk of malignant hyperthermia, with allergy to nickel/chrome or change in surgical technique
Interventions	Group 1: Acustimulation (ReliefBand) before induction of anaesthesia at P6 acupoint on dominant forearm for 24 h after surgery (n = 59) Group 2: Acu-stimulation (ReliefBand) after induction of anaesthesia at P6 acupoint on dominant forearm for 24 h after surgery (n = 53) Group 3: Sham acustimulation (inactivated ReliefBand electrodes with a silicone cover) before induction of anaesthesia at P6 acupoint on dominant forearm for 24 h after surgery (n = 59) Group 4: Sham acustimulation (inactivated ReliefBand electrodes with a silicone cover) after induction of anaesthesia at P6 acupoint on dominant forearm for 24 h after surgery (n = 58)
Outcomes	Nausea (0 – 2 h), vomiting (0 – 2 h), rescue antiemetic (tropisetron 2 mg), side effects of ReliefBand (skin irritation under electrodes)
Notes	Combined Groups 1 and 2 as acustimulation group, and Groups 3 and 4 as sham group for analysis. No cumulative incidence of 0 – 24 h outcomes reported. No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient details.
Allocation concealment (selection bias)	Unclear risk	Participants randomized by “drawing a sealed envelope indicating treatment assignment.” No details about envelopes being opaque
Blinding of patients (performance bias) All outcomes	Low risk	Authors made efforts to inactivate electrodes and place a silicone cover over the device which “was invisible for both patients and investigators.”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	Authors made efforts to inactivate electrodes and place a silicone cover over the device which “was invisible for both patients and investigators.”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Patients were evaluated for the occurrence of nausea, retching, vomiting, pain and potential side effects of ReliefBand (skin irritation under the electrodes) by an investigator unaware of the patients’ group assignment.”
Incomplete outcome data (attrition bias) All outcomes	Low risk	29 did not receive allocated intervention because of change of surgical technique. No missing data reported for the 200 participants analysed
Selective reporting (reporting bias)	Low risk	All expected outcomes reported. Authors stated “the requirement for rescue medication did not differ significantly between the treatment groups.”
Other bias	Low risk	“The demographic and morphometric characteristics and factors likely to influence PONV were not significantly different in the acu-stimulation and sham groups as were intraoperative variables.”
Gan 2004
Methods	Parallel-group randomized trial, conducted in United States. Study dates not reported
Participants	77 women undergoing major breast surgery. Exclusion: pregnancy, using permanent cardiac pacemaker, previous experience of acupuncture therapies, received any antiemetic medication or had nausea, vomiting or retching within 24 h of surgery. 2 women withdrew from study
Interventions	Group 1: ondansetron 4 mg IV given at induction of anaesthesia and sham electro-acupoint stimulation at P6 acupoints (30 – 60 min before induction and continued to the end of surgery) (n = 25) Group 2: electro-acupoint stimulation at P6 bilaterally (30 – 60 min before induction and continued to the end of surgery) and saline IV given at induction of anaesthesia (n = 26) Group 3: sham electro-acupoint stimulation at P6 bilaterally (30 – 60 min before induction and continued to the end of surgery) and saline IV given at induction of anaesthesia (n = 24)
Outcomes	Nausea (0 – 2 h), vomiting (0 – 2 h), risk of rescue antiemetic drug, adverse effects
Notes	Rescue antiemetic was dexamethasone 8 mg IV when participant’s nausea score > 5 out of 10 for 15 min or longer, 2 emetic episodes within 15 min, or at participant’s request. No redness residue on acupoint site in any groups No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Randomization was achieved using a random number generator..”
Allocation concealment (selection bias)	Low risk	“…In a sealed envelope technique”. “Study drugs were prepared by the pharmacists not directly involved in the study..”. Comments: the authors appeared to take steps to minimize inadequate allocation concealment
Blinding of patients (performance bias) All outcomes	Low risk	“All patients were also told that the device produced an electrical current that they may or may not feel. The screen on the unit (measuring 4 x 2 cm) was covered with an opaque tape in all groups so that the clinicians and research personnel were unaware if the unit was on or off”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“All patients were also told that the device produced an electrical current that they may or may not feel. The screen on the unit (measuring 4 x 2 cm) was covered with an opaque tape in all groups so that the clinicians and research personnel were unaware if the unit was on or off”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Postoperative data were collected by a separate research nurse not involved in the preoperative or intraoperative management of patients”
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons for withdrawals were given. No missing data reported for the 75 participants analysed
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “There was no difference in patient demographics among the groups”
Gieron 1993
Methods	Parallel-group randomized trial, conducted in Germany. Study dates not reported
Participants	90 women undergoing gynaecological operations (6 – 8 h).
Interventions	Group 1: acupressure was carried out by fastening small metal bullets at the P6 acupoint to each wrist by an elastic bandage on the morning of the operation and left on for 24 h (n = 30) Group 2: sham acupressure carried out by applying elastic bandage to P6 acupoint on the morning of the operation and left on for 24 h (n = 30) Group 3: no treatment (n = 30).
Outcomes	Nausea (0 – 6 h), vomiting (0 – 6 h), risk of rescue antiemetic (metoclopramide)
Notes	No treatment data were excluded from analysis. Also reported separate incidences of nausea and vomiting (0 – 1 h) and (6 – 24 h). No side effects identified in the trial No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	High risk	The outcome assessor was not blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for 90 participants analysed.
Selective reporting (reporting bias)	Low risk	All expected outcomes were reported.
Other bias	Low risk	Baseline characteristics were comparable. “The anthropometric data, the duration of surgery and the amount of postoperative analgesia were comparable between the three groups”
Habib 2006
Methods	Parallel-group randomized trial, conducted in United States. Study dates not reported
Participants	94 women undergoing Caesarean delivery under spinal anaesthesia. Exclusion: previous experience of acupuncture or acustimulation, had experienced vomiting or retching within 24 h before surgery, had taken on antiemetic or a glucocorticoid within 24 h before surgery, or had an implanted pacemaker or defibrillator device. 3 participants withdrew from study because of protocol violations
Interventions	Transcutaneous acupoint electrical stimulation device on P6 acupoint of the dominant hand 30 – 60 min before surgery. Participants asked to wear wristband for 24 h after surgery (n = 47) Sham transcutaneous acupoint electrical stimulation device on dorsum of wrist of the dominant hand 30 – 60 min before surgery. Participants asked to wear wristband for 24 h after surgery (n = 44)
Outcomes	Postoperative nausea (0 – 24 h), postoperative vomiting (0 – 24 h), risk of rescue antiemetic
Notes	Intraoperative nausea and vomiting data reported in the paper. Rescue antiemetic was ondansetron 4 mg IV if nausea score was 6 or more, or at participant’s request Study supported, in part, by departmental funds. No details about any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficent information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar. “For blinding, the ReliefBand was covered with opaque gauze that was taped to the wrist”
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“A separate researcher who was unaware of the patient’s randomisation collected that data…”
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons for withdrawals given. No missing data reported for 91 participants analysed
Selective reporting (reporting bias)	High risk	Side effects not reported
Other bias	Low risk	Baseline characteristics were comparable. “The two groups were similar with respect to demographics, parity, history of PONV or motion sickness, smoking status, duration of surgery, blood loss, intraoperative fluids, intraoperative IV fentanyl, intraoperative IV ephedrine, treatment for pruritus, and consumption of oxycodone/acetaminophen tablets”
Harmon 1999
Methods	Parallel-group randomized trial, conducted in Ireland. Study dates not reported
Participants	104 women undergoing laparoscopy and dye investigation. Exclusions: obesity, diabetes mellitus, and previous history of PONV
Interventions	Acupressure on P6 acupoint of right wrist, applied immediately before induction for 20 min, removed before end of surgery (n = 52) Sham acupressure on non-acupoint site, applied before induction for 20 min and removed before end of surgery (n = 52)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), risk of rescue antiemetic drugs
Notes	Rescue antiemetic was ondansetron 4 mg IV and prochlorperazine 12.5 mg IM. No side effects in either group noted. Some participants did not have outcome data No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Randomization was conducted by computer..”.
Allocation concealment (selection bias)	Unclear risk	“…And the code was sealed until arrival of the patient in the operating theatre”. Comment: not sure whether envelopes were sequentially numbered and opaque
Blinding of patients (performance bias) All outcomes	Low risk	“Both patients and nurses were unaware of patient group allocation”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“Both patients and nurses were unaware of patient group allocation”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“..An anaesthetist blinded to the therapy registered whether nausea, retching or vomiting had occurred”
Incomplete outcome data (attrition bias) All outcomes	High risk	In acupressure group (n = 52), missing nausea and vomiting data in 8 and 5 participants respectively. In sham group (n = 52), missing nausea and vomiting data in 13 and 5 participants respectively
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “The groups were comparable in age, weight and duration of surgical procedure”
Harmon 2000
Methods	Parallel-group randomized trial, conducted in Ireland. Study dates not reported
Participants	94 healthy women (18 – 40 years) undergoing elective Caesarean section. Exclusion: previous history of PONV, nausea and vomiting in previous 24 hours, obesity (BMI > 35), diabetes mellitus, or previous experience of acupuncture or acupressure
Interventions	Acupressure on P6 acupoint on right wrist, applied 5 min before administration of spinal anaesthesia, removed just before assessment 6 hours after discharge to the ward (n = 47) Sham acupressure on non-acupoint site, applied 5 min before administration of spinal anaesthesia, removed just before assessment 6 hours after discharge to the ward (n = 47)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h).
Notes	Reported separate incidence of intraoperative nausea and vomiting. Rescue antiemetic was ondansetron 4 mg IV during operations, or cyclizine 50 mg IM 8-hourly after operations. Rescue antiemetic use reported as mean dose (no data for risk of rescue cyclizine use). Side effect of acupressure bands was “some localized discomfort in a small number of women” No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“Bands were not visible to the assessing anaesthetist during operations, as patients’ arms were covered with surgical drapes”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“After 6 and 24h, an anaesthetist blinded to the therapy noted whether nausea, retching or vomiting had occurred”
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons for withdrawals were given. No missing data reported for 94 participants analysed
Selective reporting (reporting bias)	High risk	Risk of rescue cyclizine not reported separately for nausea and vomiting outcomes
Other bias	Low risk	Baseline characteristics were comparable. “The groups were comparable with respect to age, weight, height and bupivacaine dose”
Ho 1990
Methods	Parallel-group randomized trial, conducted in Taiwan. Study dates not reported
Participants	100 women undergoing laparoscopy.
Interventions	Group 1: electro-acupuncture applied at P6 acupoint on right wrist for 15 min in the recovery room (n = 25) Group 2: transcutaneous electrical nerve stimulation at P6 acupoint on right wrist for 15 min in the recovery room (n = 25) Group 3: antiemetic group was given prochlorperazine 5 mg IV (n = 25) Group 4: no treatment (n = 25).
Outcomes	Vomiting (0 – 3 h), side effects of treatment groups.
Notes	Reference group received no treatment and was not included in data analysis. Groups 1 and 2 were combined for data analysis, except for subgroup analysis on technique. Side effect of electro-acupuncture were sleepiness and feeling tired No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Unclear risk	Insufficient information.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data were reported for the 100 participants analysed
Selective reporting (reporting bias)	High risk	Only vomiting was reported. Authors should have assessed nausea in women and the risk of rescue antiemetic drugs
Other bias	Low risk	Baseline characteristics were comparable. “The age, weight, and duration of anaesthesia did not differ significantly among the groups”
Ho 1996
Methods	Parallel-group randomized trial, conducted in Taiwan. Study dates not reported
Participants	60 women receiving epidural morphine for post-Caesarean section pain relief. Excluded: previous carpal tunnel syndrome, or those who had experienced nausea or vomiting within 24 h before Caesarean section
Interventions	Group 1: acupressure wristbands on P6 acupoint of both wrists before administration of spinal anaesthesia. Worn for 48 hours (n = 30) Group 2: sham acupressure wristbands on both wrists but plastic button was blunted in order not to exert pressure on P6 acupoint. Worn for 48 hours (n = 30)
Outcomes	Nausea (0 – 48 h), vomiting (0 – 48 h), risk of rescue antiemetic drug, side effects of acupressure wristbands
Notes	Rescue antiemetic was metoclopramide. No side effects were noted No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Randomization was conducted by computer..”.
Allocation concealment (selection bias)	Unclear risk	“… With each code sealed in an envelope to be opened upon the parturient’s arrival in the operating room”. Comment: not sure if envelopes were sequentially numbered and opaque
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“An independent anaesthesiologist blinded to the parturient groups followed up all parturients”
Incomplete outcome data (attrition bias) All outcomes	Low risk	“All parturients completed the trial and tolerated the bands well”
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “There were no statistically significant difference with respect to age, weight, height, duration of operation, intraoperative blood loss, duration of pain relief, total epidural morphine dosage, percentage of parturients requiring additional analgesics and total time spent wearing bands between the two groups”
Iqbal 2012
Methods	Parallel-group randomized trial conducted in Pakistan from November 2011 to July 2012
Participants	60 participants aged 40 – 60 years, ASA I and II, undergoing laparoscopic surgery. Exclusion: those with a history of severe adverse reactions to NSAIDs, bronchial asthma, kidney or liver dysfunction, bleeding disorders or history of steroids intake within 24 h of surgery
Interventions	Group 1: acupressure wristband (Seaband) at the P6 acupoint to each wrist and draped with dressing during the stay in hospital. by an elastic bandage (n = 20) Group 2: sham acupressure (Seaband) on dorsal side of both forearms and draped with dressing during the stay in hospital (n = 20) Group 3: no treatment (n = 20).
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), risk of rescue antiemetic drug (metoclopramide 10 mg IV)
Notes	No treatment data were excluded from analysis. No power calculation done No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient details.
Allocation concealment (selection bias)	Unclear risk	Insufficient details.
Blinding of patients (performance bias) All outcomes	Low risk	Authors made efforts to drape dressing over active and sham wristbands
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“The doctors and nurses giving anesthesia and the nurses on the postoperative ward, although aware that stimulation was being performed were not aware of the location of PC6”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The doctors and nurses giving anesthesia and the nurses on the postoperative ward, although aware that stimulation was being performed were not aware of the location of PC6”
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data were reported for the 60 participants analysed
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Demographic data appear similar between acupressure and sham groups
Kim 2004
Methods	Parallel-group randomized trial conducted in Korea.
Participants	66 women, ASA physical status I or II, undergoing sevoflurane general anaesthesia for minor breast surgery. Exclusion criteria were women with respiratory, circulatory or neurological disease, liver or kidney dysfunction, nausea or vomiting in the 24 h before surgery, receiving antiemetics, pregnant women and excessively obesity
Interventions	Group 1: Transcutaneous electrical stimulation (ReliefBand) on P6 acupoint 10 min before surgery and left in place for 24 h. Bilateral or unilateral simulation not reported (n = 33) Group 2: Sham transcutaneous electrical stimulation (inactivated ReliefBand) on P6 acupoint 10 min before surgery and left in place for 24 h. Bilateral or unilateral sham simulation not reported (n = 33)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), risk of rescue antiemetic drug (ondansetron 4 mg IV)
Notes	Descriptive data taken from information in Kim 2012.
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient details.
Allocation concealment (selection bias)	Unclear risk	Insufficient details.
Blinding of patients (performance bias) All outcomes	Low risk	Inactivated device that looks similar to the real device.
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient details.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	Unaware of allocated treatment at both baseline and postoperative evaluations
Incomplete outcome data (attrition bias) All outcomes	Low risk	No reported dropouts or withdrawals.
Selective reporting (reporting bias)	Low risk	All expected measured outcomes were reported.
Other bias	Low risk	Baseline characteristics were comparable.
Kim 2011
Methods	Parallel-group randomized trial, conducted in Korea. Study dates not reported
Participants	264 adult women, with ASA physical status I to II, undergoing laparoscopic hysterectomy. Exclusion criteria were women receiving antiemetics within 24 h of surgery, obesity, neuromuscular, hepatic, or renal diseases, or a history of allergic reactions to the medications used during anaesthesia
Interventions	Group 1 (group control): 2 surface electrodes placed over ulnar nerve on dominant upper extremity before induction of anaesthesia and removed after anaesthesia in the operating room. Applied 1 Hz single twitch stimulation during anaesthesia maintenance (n = 54) Group 2 (group ST): 2 surface electrodes stimulated the median nerve at P6 acupoint on dominant upper extremity before induction of anaesthesia and removed after anaesthesia in the operating room. Applied 1 Hz single twitch stimulation during anaesthesia maintenance (n = 52) Group 3 (group TOF): 2 surface electrodes stimulated the median nerve at P6 acupoint on dominant upper extremity before induction of anaesthesia and removed after anaesthesia in the operating room. Applied TOF stimulation every 15 seconds during anaesthesia maintenance (n = 53) Group 4 (group DBS): 2 surface electrodes stimulated the median nerve at P6 acupoint on dominant upper extremity before induction of anaesthesia and removed after anaesthesia in the operating room. Applied double-burst stimulation every 20 seconds during anaesthesia maintenance (n = 53) Group 5 (group tetanus): 2 surface electrodes stimulated the median nerve at P6 acupoint on dominant upper extremity before induction of anaesthesia and removed after anaesthesia in the operating room. Applied tetanus stimulation at 50 Hz for 5 seconds every 10 min during anaesthesia maintenance (n = 52)
Outcomes	Nausea (0 – 6 h), Vomiting (0 – 6 h), rescue antiemetic (ondansetron 4 mg IV), side effects
Notes	Group 1 considered as sham. Groups 2 – 5 combined as 1 acustimulation group. “No side-effects were reported from the electrical stimulation.” Participants in the acustimulation group were more likely to be highly satisfied with PONV management (VAS 7 – 10) at 24 h than sham group (91% versus 75%, P = 0.003) Authors declare no conflicts of interest. No details about funding support for study
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient details given.
Allocation concealment (selection bias)	Unclear risk	Insufficient details given.
Blinding of patients (performance bias) All outcomes	Low risk	“The patients, as well as the anesthesiologist and the nursing staff, were unaware of the patient grouping.”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“The patients, as well as the anesthesiologist and the nursing staff, were unaware of the patient grouping.”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	Independent outcome assessor “was unaware of the patient randomization and of the neuromuscular monitoring mode.”
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts for 264 participants recruited into study.
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	“Baseline characteristics of study participants were similar, as were intraoperative variables.”
Klein 2004
Methods	Parallel-group randomized trial, conducted in Canada. Study dates not reported
Participants	152 people undergoing coronary artery bypass graft or valvular surgery. Exclusion: past history of hiatus hernia, heartburn, or previous gastric surgery, morbid obesity, taking antiemetic medications, H2 receptor antagonist, or proton pump inhibitors. No details about withdrawals or loss to follow-up
Interventions	Acupressure wristbands on P6 acupoint on both wrists before induction of anaesthesia, removed 24 h after extubation (n = 75) Sham acupressure wristbands on P6 acupoint of both wrists before induction of anaesthesia, removed 24 h after extubation. Sham group had band without a bead placed on P6 acupoint (n = 77)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), risk of rescue antiemetic drug, risk of adverse effects
Notes	Rescue antiemetic was dimenhydrinate 50 mg IV for participants who reported moderate or severe nausea, or who experienced retching or vomiting. No significant adverse effects reported in either group No details about any declarations of interest among authors. Acupressure bands were provided by Sea Band, United Kingdom
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Patients were randomized by computer-generated random number tables to either acupressure or placebo control groups”
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“The anaesthesiologist caring for the patient was not aware of group allocation”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“All patients were assessed for nausea and vomiting by nursing staff in the intensive care unit, who were unaware of treatment allocation”
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for the 152 participants analysed.
Selective reporting (reporting bias)	Low risk	Reported all expected outcomes.
Other bias	Low risk	Baseline characteristics were comparable. “There were no differences between the 2 groups with regard to demographic data and surgical characteristics”
Koo 2013
Methods	Parallel-group randomized trial that compared capsicum plaster stimulation of P6, K-D2 and sham acupoints. Study conducted in Korea
Participants	184 adults, aged 21 – 64 years, undergoing thyroid surgery between November 2012 and March 2013. Exclusion: obese, gastro-oesophageal reflux, use of antiemetic, histamine H2-receptor antagonist or tranquillizer within 72 hours before surgery, or respiratory disease
Interventions	Group 1: Sham P6 and K-D2 inactive tape, similar in appearance to capsicum plaster, applied to both wrists at P6 acupoint and both deltoid 30 min before induction of anaesthesia and left on for 8 h (n = 46) Group 2: Capsicum plaster applied to both wrists at P6 acupoints and inactive tape applied at both deltoids 30 min before induction of anaesthesia and left on for 8 h (n = 46) Group 3: Capsium plaster applied to both K-D2 points on index finger of hand and inactive tape applied at both deltoids 30 min before induction of anaesthesia and left on for 8 h (n = 46) Group 4: Capsium plaster applied to both deltoids and inactive tape applied to both wrists at P6 acupoint 30 min before induction of anaesthesia and left on for 8 h (n = 46)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), rescue antiemetic (metoclopramide 10 mg IV)
Notes	Groups 3 and 4 were not included in the analysis. Power calculation done. No details about financial support or conflict of interests of authors reported in article
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	“After enrolment, patients were randomized to four groups by sealed envelope.” Comment: no details about use of sequential numbering or opaque envelopes
Blinding of patients (performance bias) All outcomes	Low risk	“The patients and the investigators as well as anesthesiologists and nurses, were unaware of the patient grouping.”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“The patients and the investigators as well as anesthesiologists and nurses, were unaware of the patient grouping.”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The patients and the investigators as well as anesthesiologists and nurses, were unaware of the patient grouping.”
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants followed-up to 24 h after surgery. “There were no dropouts among the 184 enrolled subjects.”
Selective reporting (reporting bias)	High risk	Adverse effects of capsicum plaster not reported.
Other bias	Low risk	“The patients’ characteristics, such as sex, age, weight, height, duration of anesthesia, history of PONV, history of motion sickness, nonsmoking status and intraoperative remifentanil use, were comparable between groups.”
Lewis 1991
Methods	Parallel-group randomized trial, conducted in United States. Study dates not reported
Participants	66 children undergoing strabismus correction surgery. Excluded: children with anatomical or neurological abnormalities of the upper limbs. 2 children lost to follow-up
Interventions	Group 1: acupressure wristbands placed on P6 acupoints 1 h before surgery and worn until discharge from hospital (n = 33) Group 2: sham acupressure wristbands without studs placed on P6 acupoints 1 h before surgery and worn until discharge from hospital (n = 33)
Outcomes	Vomiting (0 – 24 h), risk of rescue antiemetic drug, side effects
Notes	Both types of wristbands were identical unless turned inside out. Rescue antiemetic was droperidol 0.02 mg/kg IV for vomiting. No side effects reported No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Low risk	The anaesthetic staff were blinded.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“A second blinded investigator recorded all other perioperative data, including the incidence of postoperative nausea and vomiting in the recovery areas”
Incomplete outcome data (attrition bias) All outcomes	Low risk	Two participants in acupressure group had incomplete data. Comment: unlikely to have a clinically relevant impact on summary estimate
Selective reporting (reporting bias)	High risk	Although nausea was an outcome collected in the Methods section it was not reported in the Results because nausea may be difficult to assess in children
Other bias	Low risk	Baseline characteristics were comparable. “There were no significant differences between the two groups in their patient characteristics”
Liu 2008
Methods	Parallel-group randomized trial, conducted in China. Study conducted from June 2006 to July 2007
Participants	96 people undergoing laparoscopic cholecystectomy who were aged 18 – 60 years. Exclusions: pregnancy, women experiencing menstrual symptoms, patients with permanent cardiac pace-maker, previous experience with acupuncture therapies before surgery, received antiemetics or experienced nausea, vomiting, or retching within 24 h of surgery. No participants withdrew from study
Interventions	Group 1: transcutaneous electro-acupoint stimulation using a peripheral nerve stimulator at P6 (2 – 100 Hz, 50 ms, 0.5 – 4 mA) applied 30 to 60 min before induction of anaesthesia, and continued to the end of surgery (n = 48) Group 2: inactive device with similar electrode for transcutaneous electro-acupoint stimulation using a peripheral nerve stimulator at P6 applied 30 – 60 min before induction of anaesthesia, and continued to the end of surgery (n = 48)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), risk of rescue antiemetic drug (0 – 24 h), adverse effects of transcutaneous electro-acupoint stimulation
Notes	Rescue antiemetic drug was ondansetron 4 mg IV, to participants who had a nausea score of > 5 on a 10-point scale, vomited twice within 15 min, or at the participant’s request. P6 acupoint stimulation was associated with a reduction in the risk of severe nausea (Group 1: 2/48 versus Group 2: 14/48). No redness, swelling, itching, and pain, or other relevant complications at P6 acupoint in the 2 groups No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Patients were randomized into two groups of 48 in each using a table of random numbers”
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“The anesthesiologists and care providers were blinded to the study group”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Postoperative data were collected by a separate research nurse who was not aware of the preoperative or perioperative management of patients”
Incomplete outcome data (attrition bias) All outcomes	Low risk	“All 96 patients completed the study”.
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “As shown in Tables 1 and 2, the patients’ gender, age, weight, ASA physical status, previous PONV history, duration of surgery or anaesthesia, transfusion amount, operative procedure and doses of opioids in the two groups were not significantly different”
Majholm 2011
Methods	Parallel-group randomized trial, conducted in Denmark. Study conducted from May 2005 to December 2006
Participants	134 healthy non-smoking women undergoing breast surgery given total intravenous anaesthesia. Exclusions: pregnancy, women graded ASA physical status at least III, smoked or had comorbidities that could influence sensitivity in wrists and hands, skin problems at the location of wristband or had experienced nausea or vomiting within 24 h of surgery. Of the 134 participants, 22 withdrew, leaving 112 completing the study
Interventions	Group 1: acupressure wristbands (Vital-Band) placed on P6 acupoints just before induction and worn until 24 h after surgery, covered with dressing (n = 67) Group 2: sham acupressure wristbands with studs placed on dorsum of the forearm just before induction surgery and worn until 24 h after surgery, covered with dressing (n = 67)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), risk of rescue antiemetic drug (0 – 24 h), adverse effects associated with wristband
Notes	P6 wristband adverse effects: 19/57 (redness), 7/58 (tenderness), 3/59 (paraesthesia), 8/59 (swelling). Sham wristband adverse effects: 20/53 (redness), 9/53 (tenderness), 1/53 (paraesthesia), 9/52 (swelling). Similar risk of adverse effects between groups for redness (P = 0.59), tenderness (P = 0.59), paraesthesia (P = 0.62) and swelling (P = 0.61) Manufacturer of Vital-Band paid USD 9000 for testing of their device No details about any declarations of interest among authors.
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Random allocation sequence was generated by drawing one of these sealed envelopes” and “In order to avoid staff members to figure out the randomization outcome of the last envelopes, we had more sealed randomization envelopes than needed according to the sample size calculation”
Allocation concealment (selection bias)	Low risk	“Randomized using opaque sealed envelopes”.
Blinding of patients (performance bias) All outcomes	Low risk	“The wristband was covered with a dressing in such a way that both the patient and the outcome assessors were blinded and unable to discover in which position the acupressure wristband had been applied”
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	No details available.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The wristband was covered with a dressing in such a way that both the patient and the outcome assessors were blinded and unable to discover in which position the acupressure wristband had been applied”
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons for 22 lost to follow-up and discontinued intervention were given
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable for preoperative factors (except history of PONV or motion sickness, or both), intraoperative factors and morphine use in the postoperative period
Misra 2005
Methods	Parallel-group randomized trial, conducted in India. Study dates not reported
Participants	123 adults (18 – 52 y) undergoing middle ear surgery. Exclusion: pregnancy, obesity, diabetes mellitus, impaired renal or liver functions; people who had taken H2 antagonists, antiemetics, or psychoactive medication; or had nausea, retching, or vomiting within 48 h before surgery. 3 participants withdrew because: they required administration of dexamethasone (n = 2), and facial nerve injury (n = 1)
Interventions	Group 1: sham plaster 1 cm × 1 cm patch affixed to P6 acupoint on both forearms 30 min before induction of anaesthesia and normal saline IV at the end of surgery. Plasters removed 6 h after surgery (n = 40) Group 2: capsicum plaster containing capsicum oleoresin 1% w/w 1 cm × 1 cm patch affixed to P6 acupoint on both forearms 30 min before induction of anaesthesia and normal saline IV at the end of surgery. Plasters removed 6 h after surgery (n = 38) Group 3: sham plaster 1 cm × 1 cm patch affixed to P6 acupoint on both forearms 30 min before induction of anaesthesia and ondansetron 4 mg IV at the end of surgery. Plasters removed 6 h after surgery (n = 39)
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), risk of rescue antiemetic drug (0 – 24 h), adverse effects of plaster
Notes	Nausea (0 – 6 h), vomiting (0 – 6 h), incidence of rescue antiemetic (0 – 6 h) also reported. Rescue antiemetic was ondansetron 4 mg IV for participants with persistent nausea for more than 5 min, 2 or more episodes of vomiting/retching, or at participant’s request for PONV treatment. “One patient complained of mild irritation at the site of capsicum plaster application. No other adverse effects attributable to acu-stimulation or ondansetron were observed” No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“The subjects were randomly assigned to one of the three groups using a computer-generated random number table”
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“Anesthesia was standardized and given by an anesthesiologist blinded to group assignment”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The incidence of PONV was evaluated within six hours and 24 hr after transfer to the postoperative unit by a blinded observer”
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons for withdrawals given. No missing data reported for the 120 participants analysed
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “The demographic characteristics of the three groups were similar, as were history of previous PONV and motion sickness”
Nilsson 2015
Methods	Parallel-group randomized trial, conducted in Sweden.
Participants	120 adults undergoing elective infratentorial or supratentorial craniotomy from November 2011 to June 2013. Exclusion: mental impairment or communication problems and use of antiemetics within 12 h before surgery
Interventions	Group 1: SeaBand acupressure wristband with plastic button was applied on wrist P6 acupoint (marked by neurosurgical ward nursing staff) on wrist that did not have an intra-arterial catheter at the end of surgery by a nurse anaesthetist (n = 52). Duration of acupressure wristband application was 48 h Group 2: Sham SeaBand acupressure wristband without plastic button was applied on wrist P6 acupoint (marked by neurosurgical ward nursing staff) on wrist that did not have an intra-arterial catheter at the end of surgery by a nurse anaesthetist (n = 60). Duration of sham acupressure wristband application was 48 h Prophylactic IV ondansetron 4 mg was given at the end of surgery to both groups
Outcomes	Nausea (0 – 48 h), vomiting (0 – 48 h), rescue antiemetic (0 – 48 h), adverse effects related to wristbands
Notes	Authors reported median times, not incidence, that rescue antiemetic (IV ondansetron 1 – 4 mg or droperidol 0.625 – 1.25 mg, or both) were used (0 – 48 h) for each group. No significant difference in proportion of participants requiring antiemetics between groups Power calculation done. The side effects (swelling, bruises, paraesthesia or pain) were equally distributed between P6 acupressure group (n = 7) and sham group (n = 7). Study was supported by the hospitals research foundation. Active and sham wristbands were partly provided by the manufacturer. Authors declared no conflicts of interests
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Patients were “randomly assigned to either the PC6 acupressure group or the sham group using a computer-generated random number table.”
Allocation concealment (selection bias)	Low risk	Sealed envelopes, prepared by persons not involved in study, contained information about wristband placement and presumably group allocation
Blinding of patients (performance bias) All outcomes	Low risk	“Both the PC6 acupressure bands and the sham bands were covered with a bandage to ensure blinding to the patient and outcome assessor.”
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Both the PC6 acupressure bands and the sham bands were covered with a bandage to ensure blinding to the patient and outcome assessor.”
Incomplete outcome data (attrition bias) All outcomes	Low risk	120 randomized but 95 in final analysis (43 in PC6 acupressure group and 52 in sham group). Reasons for withdrawals were described. “There was no difference between the groups in excluded patients (P = 0.406).”
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	“The 2 groups were comparable with respect to medical and demographic characteristics, anesthesia, surgical techniques, risk factors for PONV, and postoperatively administered opioids.”
Ravi 2010
Methods	Parallel-group randomized trial, conducted in India. Study dates not reported
Participants	50 people aged 4 – 60 years with ASA physical status I or II undergoing surgery (general, laparoscopic, ENT, paediatric, orthopaedic, obstetric, gynaecological) under general anaesthesia. Exclusion criteria: people with cardiovascular disease, central nervous system problems, previous history of PONV and motion sickness, and smokers
Interventions	Group 1: P6 acupoint injection with 50% 0.2 ml dextrose after induction of anaesthesia (n = 25) Group 2: Ondansetron (50 μg/kg) at end of surgery (n = 25).
Outcomes	Nausea (0 – 6 h), vomiting (0 – 6 h), rescue antiemetic (ondansetron 4 mg)
Notes	Subgroup analysis for adults and children not done as overall population was mixed in age range (4 – 60 years) No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer-generated random numbers table.
Allocation concealment (selection bias)	Unclear risk	Insufficient details given.
Blinding of patients (performance bias) All outcomes	Low risk	“Both patients and doctors were unaware of the group allocation.”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“Both patients and doctors were unaware of the group allocation.”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“An anaesthetist blinded for the study assessed the presence of nausea and vomiting.”
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for the 50 participants analysed.
Selective reporting (reporting bias)	High risk	Incidence of rescue ondansetron 4 mg for intolerable PONV in recovery room and postoperative ward not reported
Other bias	Low risk	Age, sex ratio, weight of participants and duration of surgery were similar between groups
Rusy 2002
Methods	Parallel-group randomized trial, conducted in United States. Study dates not reported
Participants	121 children (4 – 18 years) undergoing tonsillectomy with or without adenoidectomy. Exclusions: presence of skin lesions near acupuncture sites, previous and severe PONV, chronic history of nausea and vomiting. 1 child disqualified after enrolment when propofol was administered during the anaesthetic
Interventions	Electro-acupuncture at P6 for 20 min after child was awake (n = 40) Sham electro-acupuncture at P2 for 20 min after child was awake (n = 40) Sham reference group had no needles inserted. Insulated wires were attached to insides of arm and stimulation box was activated to maintain blinding (n = 40)
Outcomes	Vomiting (0 – 24 h), nausea (0 – 24 h), risk of rescue antiemetic drugs
Notes	Rescue antiemetics were ondansetron and droperidol IV. Sham electro-acupuncture and sham reference group data were combined for analysis Funding source was the Jane B Pettit Pain Foundation, Children’s Hospital of Wisconsin. No details about any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“A randomized block design procedure was used to assign enrollees to one of three groups..”
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“Experienced recovery room nurses, who were blinded to the treatment group, assessed nausea and vomiting”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Experienced recovery room nurses, who were blinded to the treatment group, assessed nausea and vomiting”
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reason for withdrawal of one participants was given. No missing data reported for 120 participants analysed
Selective reporting (reporting bias)	Unclear risk	There was no description about side effects of therapy in the trial, but in the correspondence (Rusy 2002) the authors wrote “There were no noted muscle contractions or patients who complained of paresthesias during the study”
Other bias	Low risk	Baseline characteristics were comparable. “The groups were similar for age, sex, weight, analgesics administered, and surgical time (table 1), with no differences found”
Sadighha 2008
Methods	Parallel-group randomized trial, conducted in Iran. Study dates not reported
Participants	156 adults undergoing elective laparoscopic cholecystectomy with ASA physical status I to II. Excluded: those with a history of PONV, kidney dysfunction, BMI > 35 kg/m2, use of antiemetics or H2 receptor antagonists within 72 hours of surgery, history of gastrointestinal disease, intra-abdominal pressure > 15 mm Hg, or surgery duration of more than 2 h
Interventions	Group 1: acupressure wristband at a P6 acupoint before induction until recovery discharge (n = 51) Group 2: metoclopramide 0.2 mg/kg IV at end of surgery and sham acupressure wristband at a non-acupoint before induction until recovery discharge (n = 53) Group 3: no antiemetic and had sham acupressure wristband at a non-acupoint before induction until recovery discharge (n = 52)
Outcomes	Nausea (recovery), vomiting (no time point specified).
Notes	Power calculation done. Funding source was Shaheed Beheshti University of Medical science. No details about any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	High risk	“Patients were randomly assigned to treatment groups according to the last digit of the medical record number.”
Allocation concealment (selection bias)	High risk	“Patients were randomly assigned to treatment groups according to the last digit of the medical record number.”
Blinding of patients (performance bias) All outcomes	Low risk	Authors used sham acupressure and participants given general anaesthesia would not be aware of any antiemetic drugs given at end of surgery
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient details given.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Assessors of nausea and vomiting were blinded to the treatment.”
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for 156 participants analysed.
Selective reporting (reporting bias)	High risk	No treatment side effects or rescue antiemetic use reported.
Other bias	Low risk	“Demographic and clinical characteristics of the three groups were similar.”
Samad 2003
Methods	Parallel-group randomized trial, conducted in Pakistan. Study dates not reported
Participants	50 people (18 – 60 y) undergoing laparoscopic cholecystectomy. Exclusion: obesity (weight > 80 kg), diabetics, people with history of PONV, people receiving antiemetics and histamine H2 antagonists
Interventions	Acupressure band on right hand at P6 acupoint ½ h before induction of anaesthesia, and kept on for 6 hours after surgery (n = 25) Sham acupressure band on right hand with plastic bead placed on the dorsum of forearm (n = 25)
Outcomes	Nausea (0 – 6 h), vomiting (0 – 6 h), risk of rescue antiemetic drug, side effects
Notes	Rescue antiemetic was metoclopramide 10 mg IV for nausea or vomiting. No side effects or complications associated with either intervention No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Patients were randomly assigned by random table number to either group..”
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“A blinded observer in the recovery room (one of the investigator not involved in applying acupressure band) evaluated the patients for presence of nausea and vomiting…”
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for 50 participants analysed.
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “There was no statistically significant difference with respect to age, sex, weight and duration of surgery between the two groups”
Schlager 1998
Methods	Parallel-group randomized trial, conducted in Austria. Study dates not reported
Participants	40 children (3 – 12 years) undergoing strabismus surgery. Excluded: children with gastric or intestinal disease, emesis and vomiting in the previous week, and those who received any medical therapy immediately before surgery. No child withdrew from study
Interventions	Low-level laser stimulation performed on each P6 acupoint over 30 seconds, 15 min before induction of anaesthesia and 15 min after arriving in the recovery room (n = 20) Sham laser stimulation held on P6 acupoints but laser beam not activated, 15 min before induction of anaesthesia and 15 min after arriving in the recovery room (n = 20)
Outcomes	Vomiting (0 – 24 h), risk of rescue antiemetic drug.
Notes	Rescue antiemetic was dimenhydrinate suppositories 50 mg. Nurses in the recovery room may not have been blinded to treatment groups. Vomiting (0 – 2 h, 0 – 6 h) also recorded in the paper Funding source was from Helbo-Medizintechnik GmbH and the Ludwig Boltzmann Institute for Acupuncture. No details about any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar. “Neither children nor parents were able to tell if the laser was active”
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Unclear risk	Insufficient information.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for 40 children analysed.
Selective reporting (reporting bias)	Unclear risk	Risk of nausea was not recorded because it may be difficult to assess in children. Authors stated that “stimulation of PC6 with a low-level laser has no known side effects”
Other bias	Low risk	Baseline characteristics were comparable. “There were no significant differences between the groups in age, sex distribution, ASA status, weight, height, duration of anaesthesia, duration of surgery or number of repaired muscles (table 1)”
Schultz 2003
Methods	Parallel-group randomized trial, conducted in United States. Study conducted from July 1999 to August 2000
Participants	103 women undergoing gynaecological surgery. Exclusions: pregnancy, surgery for cancer within the previous 5 years, chemotherapy or radiation therapy within 5 years, an antiemetic within 24 h before surgery, previous use of acupressure bands, or peripheral neuropathy. 40 women withdrew before completion of trial due to non-administration of study drug and change in postoperative plans due to earlier hospital discharge
Interventions	Group 1: droperidol 1.25 mg IV at induction and acupressure wristband at P6 acupoint on both wrists before surgery (worn up to 48 h after surgery) (n = 30) Group 2: droperidol 1.25 mg IV at induction and sham acupressure wristband at P6 acupoint on both wrists before surgery (worn up to 48 h after surgery). Sham acupressure wristband had flat button which did not exert pressure on P6 acupoint (n = 24) Group 3: normal saline IV at induction and acupressure wristband at P6 acupoint on both wrists before surgery (worn up to 48 h after surgery) (n = 24) Group 4: normal saline IV at induction and sham acupressure wristband at P6 acupoint on both wrists before surgery (worn up to 48 h after surgery) (n = 25)
Outcomes	Nausea (0 - duration of hospital stay), vomiting (0 - hospital stay)
Notes	Authors replied to our request for unpublished data for incidence of nausea and vomiting during hospital stay. Sea Bands were provided by manufacturer. No details about any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Used random-number table.
Allocation concealment (selection bias)	Low risk	“Study envelopes with the appropriate acupressure band and drug preparation were prepared by the principal investigator and the study pharmacist…. The packets were kept in a secure area of the surgical admitting department. The envelope, containing the study group designation, was opened by the admitting nurse…”
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Unclear risk	Insufficient information.
Incomplete outcome data (attrition bias) All outcomes	High risk	Although 40 women withdrew from the study, reasons were given. “There was no statistically significant difference in the age of the 103 women who continued in the study as compared with 40 women who did not complete the study”. Of the 103 women recruited, 95 and 62 women had complete data for nausea and vomiting during hospital stay respectively. Comment: missing data likely to bias the summary effect measure
Selective reporting (reporting bias)	High risk	Risk of side effects and use of rescue antiemetic drugs were not described in the paper
Other bias	Low risk	Baseline characteristics appeared to be comparable. There was no difference among the groups for age, type of surgery, duration of surgery, duration of acupressure wristband use
Sharma 2007
Methods	Parallel-group randomized trial, conducted in India. Study dates not reported
Participants	60 women undergoing laparoscopic cholecystectomies under general anaesthesia. Exclusion: obesity, previous history of PONV and motion sickness
Interventions	Group 1: ondansetron 4 mg IV given 10 min after induction of anaesthesia (n = 20) Group 2: bilateral P6 acupuncture 5 min before induction of anaesthesia. Intermittent stimulation was given at P6 acupoints by rotating needle clockwise and anticlockwise up to 30 min (n = 20) Group 3: combination of group 1 and group 2 interventions (n = 20)
Outcomes	Nausea (0 – 7 h), vomiting (0 – 7 h), risk of rescue antiemetic drug (0 – 7 h), risk of adverse effects
Notes	Rescue antiemetic was metoclopramide 10 mg IV. No pain, bleeding, vasovagal attack, or broken acupuncture needles noted in any of the groups No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	High risk	“Blinding of any form was not possible because acupuncture needles had to be kept in situ in the operating room”
Blinding of healthcare providers (performance bias) All outcomes	High risk	“Blinding of any form was not possible because acupuncture needles had to be kept in situ in the operating room”
Blinding of outcome assessor (detection bias) All outcomes	High risk	“Blinding of any form was not possible because acupuncture needles had to be kept in situ in the operating room”
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for 60 women analysed.
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “There was no significant difference among the patients in both the groups regarding weight, age, height, gender, hours of preoperative fasting and duration of anesthesia and surgery…”
Shenkman 1999
Methods	Parallel-group randomized trial, conducted in United States. Study dates not reported
Participants	100 children (2 – 12 y) undergoing tonsillectomy. Exclusion: congenital heart disease or significant pulmonary disease, predisposition for emesis or actual emesis in the 24 h before surgery, use of medications with antiemetic effects within the 24 h before surgery, infection over an acupuncture point, need for postoperative intubation for more than 1 h, and severe obstructive sleep apnoea
Interventions	Group 1: acupressure wristband on P6 acupoints of both wrists applied before premedication. Immediately after induction of anaesthesia, wristbands were removed and acupuncture needles were inserted at P6 acupoint on both wrists, left in place until next day. Needles were secured with a strip of tape (n = 47) Group 2: acupressure wristbands applied to sham point on both arms before premedication. Immediately after induction of anaesthesia, wristbands were removed and acupuncture needles were applied to sham point on both arms, left in place until next day. Needles were secured with a strip of tape (n = 53)
Outcomes	Vomiting (0 – 24 h), risk of rescue antiemetic drug, side effects of acupressure/acupuncture
Notes	Rescue antiemetic was ondansetron IV if 2 or more emetic episodes occurred. Combination of acupressure and acupuncture treatment effect was not analysed in subgroup analysis (invasive versus noninvasive). Proportion of acupuncture site redness and irritation was similar in both groups Funding source from National Institutes of Health General Clinical Research Centre (grant number MRR 02172). Acubands provided by Lifestyle Enterprises, New Jersey. Intradermal needles supplied by OMS Medical Supplies, Massachusetts. No details about any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar. P6 acupoints and sham points on all patients were covered with opaque adhesive tape
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“Postanesthesia care unit and ward nurses who assessed and charted postoperative emesis and medication administration were blinded to the group assignment of each patient”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Postanesthesia care unit and ward nurses who assessed and charted postoperative emesis and medication administration were blinded to the group assignment of each patient”
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for 100 participants analysed.
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “There were no differences between the groups with regard to demographics or previous retching, vomiting, or either (table 2)”
Streitberger 2004
Methods	Parallel-group randomized trial, conducted in Germany. Study was conducted between January and August 2002
Participants	212 women undergoing gynaecological or breast surgery under general anaesthesia. Exclusion: acupuncture treatment during the last 6 months, pregnancy, nausea or vomiting during the past 24 h, lymphoedema of the upper limbs, eczematous skin changes at the P6 acupoint, and coagulopathy. 1 woman in the acupuncture group withdrew consent and was treated as a failure in the analysis
Interventions	Acupuncture group: 52 participants had acupuncture to P6 acupoint on both wrists, 20 min before induction of anaesthesia; another 54 participants had acupuncture to P6 acupoint on both wrists immediately after induction of anaesthesia Sham acupuncture: 51 participants had placebo acupuncture to P6 acupoint on both wrists, 20 min before induction of anaesthesia; another 55 participants had placebo acupuncture to P6 acupoint on both wrists immediately after induction of anaesthesia
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), risk of rescue antiemetic drugs, adverse events related to acupuncture
Notes	Dimenhydinate and dolasetron rescue antiemetics used. Haematomas reported by 1 participant in the acupuncture group and by 2 participants in the placebo acupuncture group. Allergy to sticky plaster reported by 5 participants in each group. No severe adverse reaction reported Funding source from University of Heidelberg (grant number F.203583). No details about any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	“The patients were randomly distributed by type of surgery (gynaecological or breast) to ensure balance between groups“. Comment: no further details provided in the paper.
Allocation concealment (selection bias)	Low risk	“The acupuncturist obtained randomisation allocation by phone from a member of the Coordination Centre for Clinical Trials, University of Heidelberg, who had no contact with study patients. An adequate concealment was thereby assured”
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar. To assess blinding, patients were asked what kind of needle they believe they had received”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“The patients, the observer of the endpoints, the nurses, the anaesthetists and all other staff members were not informed about the allocation”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The patients, the observer of the endpoints, the nurses, the anaesthetists and all other staff members were not informed about the allocation”
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons for withdrawals given. Intention-to-treat analysis used
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “Baseline characteristics revealed no relevant differences between the two groups (table 1)”
Tavlan 1996
Methods	Parallel-group randomized trial, conducted in Turkey. Study dates not reported. This study was reported as an abstract
Participants	65 women (18 – 45 y) undergoing gynaecological laparoscopy.
Interventions	Group 1: ondansetron 8 mg IV before induction (n = 25). Group 2: 0.2 ml 50% dextrose on the P6 acupoint before induction (n = 20) Group 3: 20 ml IV saline before induction.
Outcomes	Nausea (0 – 1 h), vomiting (0 – 1 h).
Notes	Group 3 (n = 20) not used in the acupoint P6 stimulation versus sham analyses No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Unclear risk	Insufficient information.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for 65 participants analysed.
Selective reporting (reporting bias)	Unclear risk	Risk of side effects and rescue antiemetic drugs not given because the article was an abstract
Other bias	Low risk	Baseline characteristics were comparable. “No significant differences were observed between the groups in terms of demography”
Turgut 2007
Methods	Parallel-group randomized trial, conducted in Turkey. Study dates not reported
Participants	102 women aged 40 – 65 years, with no previous experience of acupressure bands, undergoing elective gynaecological surgery (total abdominal hysterectomy and bilateral salpingo-oophorectomy). 1 participant in acupressure group and 1 in sham group withdrew because of swelling and erythema in treated hand and protocol violation respectively. Exclusion criteria: obesity (BMI > 30), diabetes, history of motion sickness, PONV, or smoking
Interventions	Acupressure group: wristband with plastic bead positioned at P6 point on both wrists, 30 min before induction of general anaesthesia. Wristbands left on for 24 h (n = 51) Sham group: wristband with plastic bead positioned at non-acupoint site on the dorsal surface of both forearms, 30 min before induction of general anaesthesia. Wristbands left on for 24 h (n = 51) Both groups were educated on the use of participant-controlled analgesia before surgery. Participants received participant-controlled analgesia containing morphine in the postanaesthetic care room, and continued for 24 h
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), rescue antiemetic drug use, adverse effects of wristbands
Notes	Risks of nausea and vomiting on arrival in recovery room reported. No adverse effects or complications were observed due to acupressure wristbands, except for 1 participant in the acupressure group who withdrew due to swelling and erythema of the treated hand. Rescue antiemetic was metoclopramide 10 mg IV No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“The anaesthesiologists caring for the patients were not aware of group assignment”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The study was observer-blinded”.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons for withdrawal given. No missing data reported for 100 participants analysed
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	“Patients of both groups were comparable with regard to age, weight, height, ASA physical status and duration of surgery”
Wang 2002
Methods	Parallel-group randomized trial, conducted in United States. Study dates not reported
Participants	190 children (7 – 16 y) undergoing general anaesthesia and outpatient surgical procedures. Exclusions: ASA physical status higher than II and people with a history of developmental delay or prematurity. 3 children were excluded from study because of major study protocol violations
Interventions	Group 1: after induction, intravenous saline was given. Acupuncture at P6 acupoints on both arms was performed before end of surgery. Injection of 0.2 mL of 50% dextrose using a 1 mL tuberculin syringe with a 25-gauge needle at a depth of 5 to 7 mm from skin (n = 50) Group 2: after induction, droperidol 10 ug/kg IV was given. Superficial skin prick at the P6 acupoint was performed before end of surgery (n = 49) Group 3: after induction, intravenous saline was given. Sham point acupuncture at the dorsum of arms was performed before end of surgery. Injection of 0.2 mL of 50% dextrose using a B-D 1 mL tuberculin syringe with a 25-gauge needle at a depth of 5 to 7 mm from skin (n = 43) Group 4: after induction, intravenous saline was given. Superficial skin prick at the P6 acupoint was performed before end of surgery (n = 45)
Outcomes	Nausea (0 - recovery room), vomiting (0 - recovery room), risk of rescue antiemetic drug
Notes	Rescue antiemetic was ondansetron IV 0.1 – 4 mg/kg. Groups 3 and 4 were combined and considered as a sham group. No puncture site redness or irritation noted in any of the groups. Late outcomes (discharge to first day after surgery) also reported. No data on outcomes (0 – 24 h) according to author Funding source from Foundation of Anesthesia Education and Research, Society of Pediatric Anesthesia and National Institutes of Health (NICHD R01HD37007-01). No details about any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Yoking randomization (based on computer-generated list) was used for equal distribution of variables that are known to affect the outcome
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar. “Children, parents, surgeons, anesthesiologists, PACU nursing staff, and the research assistant, were all blinded to group assignment”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“Children, parents, surgeons, anesthesiologists, PACU nursing staff, and the research assistant, were all blinded to group assignment”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Children, parents, surgeons, anesthesiologists, PACU nursing staff, and the research assistant, were all blinded to group assignment”
Incomplete outcome data (attrition bias) All outcomes	Low risk	Details about withdrawals were given. No missing data reported for 187 children analysed
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “There were no differences among the various study groups in regard to baseline demographic characteristics such as age and history of PONV”
Wang 2010
Methods	Parallel-group randomized trial, conducted in China. Study dates not reported
Participants	80 people, aged 20 – 60 years, undergoing supratentorial craniotomy. Excluded people were obese (BMI > 30), diabetic, had a history of motion sickness or recent PONV or smoked
Interventions	Group 1: transcutaneous electrical acupoint stimulation at right wrist P6 acupoints 30 min before induction of anaesthesia, left on for 6 hours after surgery (n = 40) Group 2: sham transcutaneous electrical acupoint stimulation at non-acupoint on dorsal side of the forearm 30 min before induction of anaesthesia, left on for 6 hours after surgery (n = 40) Ondansetron 4 mg IV given as routine antiemetic treatment for each participant before skin closure in both groups
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), rescue antiemetic (metoclopramide 10 mg IV), side effects
Notes	Authors reported that no adverse effects or complications occurred associated with treatment groups No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer-generated random number table.
Allocation concealment (selection bias)	Unclear risk	Insufficient details given.
Blinding of patients (performance bias) All outcomes	Low risk	“None of the patients had experience with acupuncture electrodes.” Patients were also “unaware whether the sensation was coming from an acupoint or a non-acupoint.”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	Attending anaesthetist was blinded to treatment allocation. “The screen on the unit was covered with an opaque tape in both groups, so that clinicians and observers were unaware whether the unit was at an acupoint or not.”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	Trained nurse staff did the PONV and were blind to the position of the electrode
Incomplete outcome data (attrition bias) All outcomes	Low risk	80 participants were randomized and all completed the study.
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Demographic and perioperative characteristics in Table 1 were comparable between groups
White 2002
Methods	Parallel-group randomized trial, conducted in United States. Study dates not reported
Participants	120 adults undergoing elective plastic surgery. Excluded: antiemetic medication within 24 h before surgery, pregnancy, using permanent cardiac pacemaker, previous experience with acustimulation treatment, experiencing vomiting or retching within 24 h before surgery. No participants withdrew before discharge from hospital, 5 participants withdrew from study at 72 hours follow-up
Interventions	Group 1: ondansetron 4 mg and inactive acustimulation device (ReliefBand) at P6 acupoint on arrival in the recovery room. Device worn for 72 hours after surgery (n = 40) Group 2: saline 2 mL and active acustimulation device (ReliefBand) at P6 acupoint on arrival in the recovery room. Device worn for 72 hours after surgery (n = 40) Group 3: ondansetron 4 mg and active acu-stimulation device (ReliefBand) at P6 acupoint on arrival in the recovery room. Device worn for 72 hours after surgery (n = 40)
Outcomes	Nausea (0 - hospital discharge), vomiting (0 - hospital discharge), risk of rescue antiemetic drug, side effects
Notes	Rescue antiemetic was metoclopramide 10 mg IV if persistent nausea or vomiting, or retching lasting more than 10 min. No swelling at wrist or erythema reported. No outcome measures (0 – 72 h) given in the paper Funding source from department. First author received past funding from both Woodside Biomedical systems and GlaxoSmith-Kline
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Patients were randomly assigned to one of three treatment groups using a computer-generated random number table…”
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	All participants were told that the Relief-Band acu-stimulation device produces a sensation which they may or may not feel to minimize bias. Participants recorded outcome measures in a participant diary
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Low risk	All participants were told that the Relief-Band acustimulation device produces a sensation which they may or may not feel to minimize bias. Participants recorded outcome measures in a participant diary
Incomplete outcome data (attrition bias) All outcomes	Low risk	1 participant lost to follow-up in ondansetron group, 1 lost to follow-up in acu-stimulation group, and 3 lost to follow-up in combination group. Author used intention to treat analysis
Selective reporting (reporting bias)	Low risk	All expected outcomes were reported.
Other bias	Low risk	Baseline characteristics were comparable. “The three treatment groups were comparable with respect to demographic characteristics, pre-existing risk factors for development of PONV, and preoperative nausea scores”
White 2012
Methods	Parallel-group randomized trial, conducted in United States. Study dates not reported
Participants	100 adult outpatients, with ASA physical status I – II, undergoing major laparoscopic surgery. Exclusion criteria were people receiving antiemetic drugs within 24 hour before surgery, previous experience using acustimulation device for management of pain or emetic symptoms, history of alcohol or drug abuse within last 3 months, or a skin lesion or irritation at P6 acupoints
Interventions	Group 1: Bilaterial acupressure (Pressure Right) strips on P6 acupoints 30 – 60 min before entering operating room and left in place for 72 h after surgery. Dexamethasone 4 mg IV given before start of surgery, ondansetron 4 mg IV given at end of surgery (n = 50) Group 2: Sham acupressure (no plastic button) strips on P6 acupoints 30 – 60 min before entering operating room and left in place for 72 hours after surgery. Dexamethasone 4 mg IV given before start of surgery, ondansetron 4 mg IV given at end of surgery (n = 50)
Outcomes	Nausea (0 – 72 h), vomiting (0 – 72 h), rescue antiemetic (metoclopramide 10 mg IV and prochlorperazine 25 mg suppository), side effects of acupressure
Notes	Outcomes 0 – 24 h also reported. Participants in the acupressure group were more likely to be highly satisfied with PONV management at 72 h than sham group (mean difference 18%, 95% CI 1% to 34%). No difference in 48 h or 72 h quality of recovery score between groups. “Incidence of side-effects did not differ between the two study groups (Table 4).” Power calculation done Active and sham Pressure Right acupressure devices were provided by manufacturer. Authors declare no conflicts of interest
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer-generated randomisation scheme.
Allocation concealment (selection bias)	Unclear risk	Insufficient details given.
Blinding of patients (performance bias) All outcomes	Low risk	Strips were identical.
Blinding of healthcare providers (performance bias) All outcomes	Low risk	Placement of acupressure or sham acupressure strips by co-investigator not involved in outcome assessment
Blinding of outcome assessor (detection bias) All outcomes	Low risk	Blinded observer questioned each participant before discharge and via telephone interviews about outcomes
Incomplete outcome data (attrition bias) All outcomes	Low risk	100 participants completed the study and all participants completed the follow-up evaluations
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Demographic characteristics and history of PONV or motion sickness were not significantly different in the 2 antiemetic study groups
Xu 2012
Methods	Parallel-group randomized trial, conducted in China. Study dates not reported
Participants	130 adults, ASA physical status I – III, undergoing infratentorial craniotomy. Excluded: those with previous experiences with acupuncture, nausea or vomiting within 24 h before surgery, preoperative use of antiemetics (except dexamethasone), cardiac pacemaker, cardioverter, or defibrillator, pregnant or breastfeeding at time of surgery, obese (BMI > 35), mental retardation or psychiatric illness
Interventions	Group 1: transcutaneous electrical acupoint stimulation at dominant wrist P6 acupoints 30 min before induction of anaesthesia, left on for 24 hours after surgery (n = 65) Group 2: sham transcutaneous electrical acupoint stimulation at dominant wrist P6 acupoints 30 min before induction of anaesthesia but no electrical stimulation activated, left on for 24 h after surgery (n = 65) Ondansetron 4 mg IV and dexamethasone 10 mg given as routine antiemetic treatment for each participant during surgery in both groups
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), rescue antiemetic (metoclopramide 10 mg IM)
Notes	Power calculation done. Authors reported that no adverse effects (cutaneous irritation, bleeding, nerve injury) occurred associated with treatment groups. Authors have no conflicts of interest. Study supported by grants from Major State Basic Research Development Program of China (973 Program No. 2007CB12502) and National Natural Science Foundation of China (No. 81171235/H0914)
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer-generated random number table.
Allocation concealment (selection bias)	Low risk	Sequentially-numbered, opaque sealed envelopes.
Blinding of patients (performance bias) All outcomes	Low risk	“Display screens of the units were concealed from view for patients and other investigators… All patients were told that a tingling or numbing sensation might or might not be felt, regardless of the the group assignment.”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“Display screens of the units were concealed from view for patients and other investigators.”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“Trained nursing staff, who were blinded to the group assignments, assessed PONV…”
Incomplete outcome data (attrition bias) All outcomes	Low risk	11 (8%) participants withdrew, probably due to those who could not be extubated within 2 h after surgery or had impaired consciousness in the neurological intensive care unit
Selective reporting (reporting bias)	Low risk	All expected outcomes were reported.
Other bias	Low risk	“No differences in patient demographics, risk factors for PONV, duration of anaesthesia, intraoperative opioids and postoperative analgesic consumption between the two groups.”
Yang 1993
Methods	Parallel-group randomized trial, conducted in Taiwan. Study dates not reported
Participants	120 women undergoing gynaecological laparoscopy.
Interventions	Group 1: acupuncture group included participants given an injection of 0.2 mL 50% glucose in water into P6 acupoint before extubation (n = 40) Group 2: antiemetic group was droperidol 20 ug/kg IV on induction of anaesthesia (n = 40) Group 3: no treatment (n = 40).
Outcomes	Vomiting (0 – 3 h), side effects of acupuncture.
Notes	Reference group received no treatment and was not included in data analysis. Pain at acupoint site noted No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of healthcare providers (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessor (detection bias) All outcomes	Unclear risk	Insufficient information.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data recorded for 120 participants analysed.
Selective reporting (reporting bias)	High risk	Nausea was not reported.
Other bias	Low risk	Baseline characteristics were comparable. “There was no statistically significant differences in age, weight, duration of anesthesia or amount of fluid given among the three groups of patients”
Yentis 1992
Methods	Parallel-group randomized trial, conducted in Canada. Study dates not reported
Participants	90 children (1 – 16 y) undergoing strabismus surgery. 1 child in each of the 3 groups could not be contacted after surgery
Interventions	Group 1: acupuncture at P6 acupoint on right wrist with 5 min of manual stimulation after induction of anaesthesia (n = 30) Group 2: antiemetic group had 0.075 mg/kg droperidol IV after induction of anaesthesia (n = 30) Group 3: acupuncture (as in Group 1) and droperidol (as in Group 2) treatment (n = 30)
Outcomes	Vomiting (0 – 48 h), risk of rescue antiemetic drug, side effects of treatment
Notes	Rescue antiemetic was dimenhydrinate IM. Restlessness more frequent in droperidol group than acupuncture group. Risk of vomiting before discharge from hospital also reported in paper No details about funding source or any declarations of interest among authors
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	“Whether or not patients received droperidol, both treatments or acupuncture alone, was unknown to the staff, the patients and their parents”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“Whether or not patients received droperidol, both treatments or acupuncture alone, was unknown to the staff, the patients and their parents”
Blinding of outcome assessor (detection bias) All outcomes	Unclear risk	Insufficient information.
Incomplete outcome data (attrition bias) All outcomes	Low risk	One participant in each group lost to follow-up. Comment: unlikely to bias summary estimate.
Selective reporting (reporting bias)	High risk	Need for rescue antiemetic not reported in Results. Nausea was not reported because it may have been difficult to assess in younger children
Other bias	Low risk	Baseline characteristics were comparable. “Age, weight, number of muscles repaired and duration of anaesthesia did not differ among the groups”
Zhu 2010
Methods	Parallel-group randomized trial, conducted in China. Study dates not reported
Participants	120 women undergoing gynaecological laparoscopic surgery, ASA I – II, for general anaesthesia
Interventions	Group 1: dilute droperidol injected into bilateral P6 acupoints using an acupuncture needle at 20 min before surgery. Twisted needle at depth of 2.5 cm to 3 cm to get needling sensation, and retained for 10 min (n = 40) Group 2: 2.5 mg droperidol IV 20 minutes before surgery (n = 40) Group 3: no treatment.
Outcomes	Nausea (0 – 24 h), vomiting (0 – 24 h), side effects of droperidol
Notes	No treatment data were excluded from analysis. No drowsiness, anxiety or extrapyramidal reactions observed in any groups No details about any declarations of interest among authors.
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants were randomized into 3 groups using a random-numbers table
Allocation concealment (selection bias)	Unclear risk	Sequential but no other details given.
Blinding of patients (performance bias) All outcomes	High risk	Participants unlikely to be blinded as they were conscious in order to feel needling sensation of acupuncture
Blinding of healthcare providers (performance bias) All outcomes	High risk	No attempt to mask sham acupuncture in droperidol group.
Blinding of outcome assessor (detection bias) All outcomes	Unclear risk	Insufficient details given.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data recorded for 120 participants analysed.
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Age and type of surgery among groups were comparable.
Zárate 2001
Methods	Parallel-group randomized trial, conducted at 4 university centres in United States. Study dates not reported
Participants	250 adults undergoing laparoscopic cholecystectomy. Excluded: people who had taken antiemetic, glucocorticosteroids, or psychoactive medication within 24 hours before the operation; were pregnant; had an implanted cardiac pacemaker or defibrillator device; or had experienced vomiting or retching within 24 h before surgery. 29 adults were excluded because of protocol violations
Interventions	Group 1: ReliefBand (watch-like acustimulation device) positioned at P6 acupoint before the end of surgery. The device was set to deliver a 25 mA stimulus at 31 Hz. Participants wore the device for 9 hours after surgery (n = 110) Group 2: ReliefBand with no acustimulation positioned at P6 acupoint before end of surgery, worn up to 9 hours after surgery (n = 56) Group 3: ReliefBand with no acustimulation positioned at the dorsal aspect of the wrist before end of surgery, worn up to 9 hours after surgery (n = 55)
Outcomes	Nausea (0 - arrival in recovery room), vomiting (0 - arrival in recovery room), risk of rescue antiemetic (0 – 2 h), side effects of wristband. Rescue antiemetics were droperidol 0.625 mg IV and ondansetron 4 mg IV
Notes	Group 2 and Group 3 were considered as the sham control group for data analysis. Although the ReliefBand devices were identical in appearance, their placement on the dorsal side of the wrist would have suggested that the participants were in Group 3. Outcomes also evaluated at 45, 90, 120, 240, 360 and 540 min after surgery. No cumulative data recorded (requested data from authors but no reply). Side effects of wristbands were mild cutaneous irritation with erythema Study supported by grants from Woodside Biomedical Inc and the White Mountain Institute. The second and third authors are paid consultants for Woodside Biomedical Inc
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Outpatients who had been fasted overnight were randomly assigned to one of three treatment groups (groups T, S, and P) with a computer-generated random number table”
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar. “To minimize bias resulting from the presence or absence of the electrical stimulation, all patients were told before the operation that the ReliefBand produces a sensation which ’they might or might not feel”
Blinding of healthcare providers (performance bias) All outcomes	Low risk	“The recovery room nursing staff were unaware of the acu-stimulation treatment group to which the patient had been assigned”
Blinding of outcome assessor (detection bias) All outcomes	Low risk	“The recovery room nursing staff were unaware of the acu-stimulation treatment group to which the patient had been assigned”
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons for withdrawals were given. No missing data recorded for 221 participants analysed
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. “The three treatment groups were comparable demographically and with respect to their histories of PONV and motion sickness, baseline nausea score, duration of surgery, and the time the acu-stimulation device was applied before the end of surgery”

ASA = American Society of Anesthesiologists

BMI = body mass index

cm = centimetres

DBS = double burst stimulation

ENT = Ear, nose, throat

h = hour

Hz = Hertz

H2 = selective histamine type 2 receptor

IM = intramuscular

IV = intravenous

K-D2 = Korean hand acupuncture K-D2 point

Kg = kilograms

mA = milliamperes

mg = milligrams

ml = millilitres

mm = millimetres

n = number of participants

NSAIDs = nonsteroidal anti-inflammatory drugs

P6 = pericardium acupoint

PACU = postoperative anaesthesia care unit

PC = pericardium acupoint

PONV = postoperative nausea and vomiting

ST = single twitch

TENS = transcutaneous electrical nerve stimulation

TOF = train-of-four

VAS = visual analogue scale

y = years