Stimulation of the wrist acupuncture point PC6 for preventing postoperative nausea and vomiting

Anna Lee; Simon KC Chan; Lawrence TY Fan

doi:10.1002/14651858.CD003281.pub4

. 2015 Nov 2;2015(11):CD003281. doi: 10.1002/14651858.CD003281.pub4

Stimulation of the wrist acupuncture point PC6 for preventing postoperative nausea and vomiting

Anna Lee ^1,^2,^✉, Simon KC Chan ¹, Lawrence TY Fan ¹

Editor: Cochrane Anaesthesia Group

PMCID: PMC4679372 NIHMSID: NIHMS736151 PMID: 26522652

Abstract

Background

Postoperative nausea and vomiting (PONV) are common complications following surgery and anaesthesia. Antiemetic drugs are only partially effective in preventing PONV. An alternative approach is to stimulate the PC6 acupoint on the wrist. This is an update of a Cochrane review first published in 2004, updated in 2009 and now in 2015.

Objectives

To determine the effectiveness and safety of PC6 acupoint stimulation with or without antiemetic drug versus sham or antiemetic drug for the prevention of PONV in people undergoing surgery.

Search methods

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library, Issue 12, 2014), MEDLINE (January 2008 to December 2014), EMBASE (January 2008 to December 2014), ISI Web of Science (January 2008 to December 2014), World Health Organization Clinical Trials Registry, ClinicalTrials.gov, and reference lists of articles to identify additional studies. We applied no language restrictions.

Selection criteria

All randomized trials of techniques that stimulated the PC6 acupoint compared with sham treatment or drug therapy, or combined PC6 acupoint and drug therapy compared to drug therapy, for the prevention of PONV. Interventions used in these trials included acupuncture, electro‐acupuncture, transcutaneous electrical acupoint stimulation, transcutaneous nerve stimulation, laser stimulation, capsicum plaster, acu‐stimulation device, and acupressure in people undergoing surgery. Primary outcomes were the incidences of nausea and vomiting after surgery. Secondary outcomes were the need for rescue antiemetic therapy and adverse effects.

Data collection and analysis

Two review authors independently extracted the data and assessed the risk of bias domains for each trial. We used a random‐effects model and reported risk ratio (RR) with associated 95% confidence interval (95% CI). We used trial sequential analyses to help provide information on when we had reached firm evidence in cumulative meta‐analyses of the primary outcomes, based on a 30% risk ratio reduction in PONV.

Main results

We included 59 trials involving 7667 participants. We rated two trials at low risk of bias in all domains (selection, attrition, reporting, blinding and other). We rated 25 trials at high risk in one or more risk‐of‐bias domains. Compared with sham treatment, PC6 acupoint stimulation significantly reduced the incidence of nausea (RR 0.68, 95% CI 0.60 to 0.77; 40 trials, 4742 participants), vomiting (RR 0.60, 95% CI 0.51 to 0.71; 45 trials, 5147 participants) and the need for rescue antiemetics (RR 0.64, 95% CI 0.55 to 0.73; 39 trials, 4622 participants). As heterogeneity among trials was substantial and there were study limitations, we rated the quality of evidence as low. Using trial sequential analysis, the required information size and boundary for benefit were reached for both primary outcomes.

PC6 acupoint stimulation was compared with six different types of antiemetic drugs (metoclopramide, cyclizine, prochlorperazine, droperidol. ondansetron and dexamethasone). There was no difference between PC6 acupoint stimulation and antiemetic drugs in the incidence of nausea (RR 0.91, 95% CI 0.75 to 1.10; 14 trials, 1332 participants), vomiting (RR 0.93, 95% CI 0.74 to 1.17; 19 trials, 1708 participants), or the need for rescue antiemetics (RR 0.87, 95% CI 0.65 to 1.16; 9 trials, 895 participants). We rated the quality of evidence as moderate, due to the study limitations. Using trial sequential analyses, the futility boundary was crossed before the required information size was surpassed for both primary outcomes.

Compared to antiemetic drugs, the combination of PC6 acupoint stimulation and antiemetic therapy reduced the incidence of vomiting (RR 0.56, 95% CI 0.35 to 0.91; 9 trials, 687 participants) but not nausea (RR 0.79, 95% CI 0.55 to 1.13; 8 trials, 642 participants). We rated the quality of evidence as very low, due to substantial heterogeneity among trials, study limitations and imprecision. Using trial sequential analysis, none of the boundaries for benefit, harm or futility were crossed for PONV. The need for rescue antiemetic was lower in the combination PC6 acupoint stimulation and antiemetic group than the antiemetic group (RR 0.61, 95% CI 0.44 to 0.86; 5 trials, 419 participants).

The side effects associated with PC6 acupoint stimulation were minor, transient and self‐limiting (e.g. skin irritation, blistering, redness and pain) in 14 trials. Publication bias was not apparent in the contour‐enhanced funnel plots.

Authors' conclusions

There is low‐quality evidence supporting the use of PC6 acupoint stimulation over sham. Compared to the last update in 2009, no further sham comparison trials are needed. We found that there is moderate‐quality evidence showing no difference between PC6 acupoint stimulation and antiemetic drugs to prevent PONV. Further PC6 acupoint stimulation versus antiemetic trials are futile in showing a significant difference, which is a new finding in this update. There is inconclusive evidence supporting the use of a combined strategy of PC6 acupoint stimulation and antiemetic drug over drug prophylaxis, and further high‐quality trials are needed.

Keywords: Humans, Acupuncture Points, Wrist, Antiemetics, Antiemetics/therapeutic use, Postoperative Nausea and Vomiting, Postoperative Nausea and Vomiting/prevention & control, Randomized Controlled Trials as Topic

Plain language summary

Wrist PC6 acupuncture point stimulation to prevent nausea and vomiting after surgery

Review question

Does a review of the evidence support the use of wrist PC6 acupuncture point stimulation (PC6 acupoint) as effective in reducing nausea and vomiting after surgery (PONV), compared to sham (dummy acupoint stimulation) or antiemetics (drugs that relieve nausea and vomiting) in people undergoing surgery? This review updates the evidence published in 2009, and is current to December 2014.

Background

Nausea and vomiting are two of the most common complications (up to 80%) after anaesthesia and surgery. Antiemetics are only partially effective and may cause adverse effects, like sedation and headache. Stimulating a PC6 acupoint, an alternative method, has been reported to reduce PONV with few serious side effects.

Study characteristics

We found 59 relevant studies, conducted between 1986 and 2015, involving 7667 participants undergoing elective surgery. Seven of the trials were conducted in 727 children. The PC6 acupoint stimulation varied from invasive techniques, such as traditional acupuncture needles, to noninvasive techniques, such as acupressure wristbands. PC6 acupoint stimulation was compared with six different types of antiemetic drugs (metoclopramide, cyclizine, prochlorperazine, droperidol. ondansetron and dexamethasone).

Key findings and quality of evidence

Effects of PC6 acupoint stimulation versus sham on PONV

We found a moderate‐size effect in children and adults, although there were concerns about study limitations and unexplained variation in the effects. Further studies with sham comparisons are not necessary to confirm this beneficial effect.

Effects of PC6 acupoint stimulation versus antiemetic on PONV

We found no difference in the incidence of PONV. We rated the quality of this evidence as moderate, due to study limitations. Further studies are unlikely to show a difference.

Effects of combining PC6 acupoint stimulation and antiemetic versus antiemetic on PONV

We found a moderate‐size effect on postoperative vomiting but not on postoperative nausea. However, there were concerns about study limitations, unexplained variation in effects between studies, and an insufficient number of studies. Further high‐quality research on combinations of PC6 acupoint stimulation and antiemetics are needed to reduce uncertainties about this effect on PONV.

Overall, the side effects related to PC6 acupoint stimulation were minor, transient and self‐limiting (e.g. skin irritation, blistering, redness and pain) in 14 studies.

Conclusion

To prevent PONV, the effect of PC6 acupoint stimulation is comparable to antiemetics.

Summary of findings

Summary of findings for the main comparison. Acupoint PC6 stimulation versus sham for preventing postoperative nausea and vomiting.

Acupoint PC6 stimulation versus sham for preventing postoperative nausea and vomiting
Patient or population: People at risk of postoperative nausea and vomiting  Settings: Surgery  Intervention: Acupoint PC6 stimulation Comparison: Sham
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect  (95% CI)	No of Participants  (studies)	Quality of the evidence  (GRADE)	Comments
	Assumed risk	Corresponding risk
	Sham	Acupoint PC6 stimulation
Nausea ‐ All trials	Low		RR 0.68   (0.60 to 0.77)	4742  (40 studies)	⊕⊕⊝⊝  low^1,2
	200 per 1000	136 per 1000   (120 to 154)
	Moderate
	400 per 1000	272 per 1000   (240 to 308)
	High
	600 per 1000	408 per 1000   (360 to 462)
Vomiting ‐ All trials	Low		RR 0.60   (0.51 to 0.71)	5147  (45 studies)	⊕⊕⊝⊝  low^2,3
	200 per 1000	120 per 1000   (102 to 142)
	Moderate
	400 per 1000	240 per 1000   (204 to 284)
	High
	600 per 1000	360 per 1000   (306 to 426)
Rescue antiemetics	329 per 1000	210 per 1000   (181 to 240)	RR 0.64   (0.55 to 0.73)	4622  (39 studies)	⊕⊕⊝⊝  low^4,5
Adverse effects	Not estimable	Not estimable	Not estimable	35 studies⁶	Not applicable	See footnote⁶
The basis for the assumed risks* for nausea and vomiting is from a consensus panel (Gan 2014) using Apfel's simplified risk score (Apfel 1999). The assumed risk for rescue antiemetic is the median sham group risk across studies. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).  CI: Confidence interval; RR: Risk ratio;
GRADE Working Group grades of evidence  High quality: Further research is very unlikely to change our confidence in the estimate of effect.  Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.  Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.  Very low quality: We are very uncertain about the estimate.

Acupoint PC6 stimulation versus antiemetic drug for preventing postoperative nausea and vomiting
Patient or population: People at risk of postoperative nausea and vomiting  Settings: Surgery  Intervention: Acupoint PC6 stimulation Comparison: Antiemetic drug
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect  (95% CI)	No of Participants  (studies)	Quality of the evidence  (GRADE)	Comments
	Assumed risk	Corresponding risk
	Antiemetic	Acupoint PC6 stimulation
Nausea ‐ All antiemetics combined	Low		RR 0.91   (0.75 to 1.10)	1332  (14 studies)	⊕⊕⊕⊝  moderate¹
	200 per 1000	182 per 1000   (150 to 220)
	Moderate
	400 per 1000	364 per 1000   (300 to 440)
	High
	600 per 1000	546 per 1000   (450 to 660)
Vomiting ‐ All antiemetics combined	Low		RR 0.93   (0.74 to 1.17)	1708  (19 studies)	⊕⊕⊕⊝  moderate²
	200 per 1000	186 per 1000   (148 to 234)
	Moderate
	400 per 1000	372 per 1000   (296 to 468)
	High
	600 per 1000	558 per 1000   (444 to 702)
Rescue antiemetic	150 per 1000	130 per 1000   (97 to 174)	RR 0.87   (0.65 to 1.16)	895  (9 studies)	⊕⊕⊕⊝  moderate³
Adverse effects	See comment	See comment	Not estimable	11 studies⁴	Not applicable	See footnote⁴
The basis for the assumed risks* for nausea and vomiting is from a consensus panel (Gan 2014) using Apfel's simplified risk score (Apfel 1999). The assumed risk for rescue antiemetic is the median antiemetic group risk across studies. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).  CI: Confidence interval; RR: Risk ratio;
GRADE Working Group grades of evidence  High quality: Further research is very unlikely to change our confidence in the estimate of effect.  Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.  Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.  Very low quality: We are very uncertain about the estimate.

Acupoint PC6 stimulation and antiemetic combination compared to antiemetic for preventing postoperative nausea and vomiting
Patient or population: People at risk of postoperative nausea and vomiting  Settings: Surgery  Intervention: Acupoint PC6 stimulation and antiemetic combination  Comparison: Antiemetic drug
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect  (95% CI)	No of Participants  (studies)	Quality of the evidence  (GRADE)	Comments
	Assumed risk	Corresponding risk
	Antiemetic	Acupoint PC6 stimulation and antiemetic combination
Nausea	Low		RR 0.79   (0.55 to 1.13)	642  (8 studies)	⊕⊝⊝⊝  very low^1,2,3
	200 per 1000	158 per 1000   (110 to 226)
	Moderate
	400 per 1000	316 per 1000   (220 to 452)
	High
	600 per 1000	474 per 1000   (330 to 678)
Vomiting	Low		RR 0.56   (0.35 to 0.91)	687  (9 studies)	⊕⊝⊝⊝  very low^3,4,5
	200 per 1000	112 per 1000   (70 to 182)
	Moderate
	400 per 1000	224 per 1000   (140 to 364)
	High
	600 per 1000	336 per 1000   (210 to 546)
Rescue antiemetic	316 per 1000	193 per 1000   (139 to 272)	RR 0.61   (0.44 to 0.86)	419  (5 studies)	⊕⊕⊝⊝  low^3,6
Adverse effects	See comment	See comment	Not estimable	6 studies⁷	Not applicable	See footnote⁷
The basis for the assumed risks* for nausea and vomiting is from a consensus panel (Gan 2014) using Apfel's simplified risk score (Apfel 1999). The assumed risk for rescue antiemetic is the median antiemetic group risk across studies. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).  CI: Confidence interval; RR: Risk ratio;
GRADE Working Group grades of evidence  High quality: Further research is very unlikely to change our confidence in the estimate of effect.  Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.  Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.  Very low quality: We are very uncertain about the estimate.

Control event rate	Nausea	95% CI	Vomiting	95% CI
10%	31	25 to 43	25	20 to 34
20%	16	13 to 22	13	10 to 17
30%	10	8 to 14	8	7 to 11
40%	8	6 to 11	6	5 to 9
50%	6	5 to 9	5	4 to 7
60%	5	4 to 7	4	3 to 6
70%	4	4 to 6	4	3 to 5
80%	4	3 to 5	3	3 to 4
90%	3	3 to 5	3	2 to 4

Date	Event	Description
30 October 2015	New search has been performed	We have performed a new search. We reran the searches until December 2014.
30 October 2015	New citation required and conclusions have changed	We have made the following changes from the previous published review (Lee 2009) in this updated review. 1. In keeping with World Health Organization International Acupuncture Nomenclature, we abbreviate the Pericardium acupoint as PC6. 2. We found 19 new completed trials and 2 new ongoing trials, which changed the previously published review's conclusions (Lee 2009) . 3. We include trial sequential analyses in this update. 4. A change in members of the review team from the first published review to the present update. Another author (Chan) has joined the review team.
8 December 2010	Amended	Contact details updated.
10 October 2008	New search has been performed	The searches were rerun until September 2008
10 October 2008	New citation required and conclusions have changed	The following changes from the previous published review are made in this updated review. We found 14 new studies which changed the previously published review's conclusions. We have incorporated risk of bias and summary of findings tables. A change in members of the review team from the first published review to the present update. One of the original authors (Done) was unavailable, and another author (Fan) has joined the review team.
9 January 2008	Amended	Converted to new review format.
13 July 2004	Amended	"Stimulation of the wrist acupuncture point P6 for preventing postoperative nausea and vomiting" was published as a protocol under the title: "Acupoint P6 stimulation for preventing postoperative nausea and vomiting".

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Nausea	40		Risk Ratio (IV, Random, 95% CI)	Subtotals only
1.1 All trials	40	4742	Risk Ratio (IV, Random, 95% CI)	0.68 [0.60, 0.77]
1.2 Children	2	258	Risk Ratio (IV, Random, 95% CI)	0.63 [0.51, 0.80]
1.3 Adults	36	4344	Risk Ratio (IV, Random, 95% CI)	0.70 [0.61, 0.79]
1.4 Invasive PC6 stimulation	7	896	Risk Ratio (IV, Random, 95% CI)	0.56 [0.39, 0.80]
1.5 Noninvasive PC6 stimulation	33	3846	Risk Ratio (IV, Random, 95% CI)	0.71 [0.62, 0.81]
1.6 Low risk of bias trials	2	169	Risk Ratio (IV, Random, 95% CI)	0.40 [0.17, 0.93]
1.7 Unclear risk of bias trials	20	2496	Risk Ratio (IV, Random, 95% CI)	0.68 [0.56, 0.82]
1.8 High risk of bias trials	11	1090	Risk Ratio (IV, Random, 95% CI)	0.68 [0.55, 0.85]
1.9 Trials with control event rate less than or equal to 20%	4	454	Risk Ratio (IV, Random, 95% CI)	0.81 [0.49, 1.33]
1.10 Trials with control event rate more than 20%	36	4288	Risk Ratio (IV, Random, 95% CI)	0.68 [0.59, 0.77]
2 Vomiting	45		Risk Ratio (IV, Random, 95% CI)	Subtotals only
2.1 All trials	45	5147	Risk Ratio (IV, Random, 95% CI)	0.60 [0.51, 0.71]
2.2 Children	6	542	Risk Ratio (IV, Random, 95% CI)	0.67 [0.46, 0.97]
2.3 Adults	37	4465	Risk Ratio (IV, Random, 95% CI)	0.61 [0.51, 0.72]
2.4 Invasive PC6 stimulation	7	896	Risk Ratio (IV, Random, 95% CI)	0.51 [0.34, 0.76]
2.5 Noninvasive PC6 stimulation	37	4151	Risk Ratio (IV, Random, 95% CI)	0.60 [0.50, 0.73]
2.6 Low risk of bias trials	2	169	Risk Ratio (IV, Random, 95% CI)	0.52 [0.31, 0.88]
2.7 Unclear risk of bias trials	26	3583	Risk Ratio (IV, Random, 95% CI)	0.59 [0.48, 0.72]
2.8 High risk of bias trials	14	1373	Risk Ratio (IV, Random, 95% CI)	0.62 [0.45, 0.83]
2.9 Trials with control event rate less than or equal to 20%	12	1556	Risk Ratio (IV, Random, 95% CI)	0.75 [0.51, 1.11]
2.10 Trials with control event rate more than 20%	33	3591	Risk Ratio (IV, Random, 95% CI)	0.58 [0.48, 0.69]
3 Rescue antiemetics	39	4622	Risk Ratio (IV, Random, 95% CI)	0.64 [0.55, 0.73]

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.

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".

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.

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."

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".

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.

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.

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."

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.

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."

Study	Reason for exclusion
Agarwal 2005	PC6 acupoint stimulation not used. Authors used Korean hand acupressure point K‐D2 in the study.
Al‐Sadi 1997	No sham treatment group used. Control was defined as no intraoperative acupuncture needle at PC6 acupoint.
Alkaissi 2005	Participants did not undergo surgery.
Cekmen 2007	PC6 acupoint stimulation not used. Authors used transcutaneous electrical nerve stimulation on neck and mastoid area.
Chen 2005	No sham treatment group used.
Coloma 2002	Treatment of established postoperative nausea and vomiting.
Dundee 1988	Incidences of nausea and vomiting were not reported separately.
Dundee 1991	2 different forms of PC6 stimulation (acupuncture + saline, acupuncture + 1% lidocaine). No sham treatment group used.
El‐Bandrawy 2013	Severity of nausea and vomiting symptoms assessed, not incidence.
El‐Rakshy 2009	Multiple acupoints used.
Fan 1997	Incidences of nausea and vomiting were not reported separately.
Fry 1986	No sham treatment group used. Control was defined as no acupressure treatment. Participants did not know that they were in the trial.
Grube 2009	Multiple acupoints used (Hegu, Quchi, Neiguan, Zusanli, Neiting, Sanyinjiao, Daichong).
Hirs 2013	Ambiguous details about group allocation following results of unpublished pilot study.
Ho 2006	Prevention of intraoperative nausea and vomiting, not postoperative outcomes.
Jin 2013	No sham PC6 acupoint stimulation group.
Kabalak 2005	Both Pericardium and Shangwan acupoints used. No treatment was given to the control group.
Khan 2004	Incidences of nausea and vomiting were not reported separately.
Kim 2002	Control was defined as an inactive capsicum plaster tape fixed at the Korean hand acupuncture point K‐D2 point of both hands.
Kim 2010	Control group appears to be no‐treatment. Unable to get full text.
Klaiman 2008	Incidences of nausea and vomiting were not reported separately.
Korinenko 2009	Multiple acupoints used.
Larson 2010	Severity of nausea and vomiting symptoms assessed, not incidence.
Lee 2008	No sham treatment group used.
Lee 2013	No sham treatment group used.
Liodden 2011	Control group was standard care without acupuncture/acupressure.
Lu 2013	No sham treatment group used.
McConaghy 1996	Treatment of established postoperative nausea and vomiting.
McMillan 1994	All transcutaneous electrical stimulation at PC6 acupoint groups received antiemetics. Incidences of nausea and vomiting were not reported separately for placebo transcutaneous electrical stimulation and transcutaneous electrical stimulation groups.
Ming 2002	Multiple acupoints used.
Ng 2011	Incidences of nausea and vomiting were not reported separately.
Norheim 2010	Control group was standard care without acupuncture/acupressure.
Noroozinia 2013	Prevention of intraoperative nausea and vomiting, as well as postoperative nausea and vomiting. Unclear how long acupressure wristband was applied on for. Metoclopramide given for intraoperative nausea and vomiting will affect subsequent PONV incidence comparisons.
Ouyang 2009	No sham treatment group used. Control was defined as no acupuncture at PC6 acupoint before and during anaesthesia.
Phillips 1994	No sham treatment group used. No specific details of the type of antiemetic drug used as control.
Schwager 1996	Both PC6 and Li4 acupoints stimulated.
Shyr 1990	Control was defined as no acupuncture at PC6 acupoint.
Sinha 2011	Nausea and vomiting during labour and delivery, not postoperative outcomes.
Somri 2001	Multiple acupoints used.
Stein 1997	Prevention of intraoperative nausea and vomiting.
Tang 2013	No sham treatment group used.
Wang 2014	Multiple acupoints used.
Weightman 1987	No sham treatment group used. Control was defined as no acupuncture at PC6 acupoint after induction of anaesthesia.
White 2005	This study compared 3 prophylactic acu‐stimulation treatments: preoperative, postoperative, and both preoperative and postoperative. No sham treatment group used for both preoperative and postoperative acu‐stimulation.
Windle 2001	Retrospective chart review was used to estimate the incidence of vomiting. Incidences of nausea and vomiting were not considered separately, and results were not presented in the paper.
Yeh 2010	Multiple acupoints used for pain and PONV.
Yentis 1991	No sham treatment group used. Control was no acupuncture treatment at PC6 acupoint.
Yentis 1998	This study compared acupuncture given before induction, after induction and in the recovery room. No sham treatment or antiemetic drug group for comparison.
Zheng 2008	Multiple acupoints used.

Trial name or title	PC6 acupoint stimulation for prevention of postoperative nausea and vomiting in patients undergoing cardiac surgery
Methods	2‐centred, double‐blinded, 2‐arm, parallel‐group RCT
Participants	People undergoing primary cardiac surgery
Interventions	Group 1: Seaband wristband applied bilaterally to PC6 acupoint on arrival to ICU, covered by light opaque bandage for 36 hours. Group 2: Sham Seaband wristband without stud applied to both wrists on arrival to ICU, covered by light opaque bandage for 36 hours.
Outcomes	Nausea (0 ‐ 6 h, 0 ‐ 12 h, 0 ‐ 24 h, 0 ‐ 36 h), vomiting (0 ‐ 6 h, 0 ‐ 12 h, 0 ‐ 24 h, 0 ‐ 36 h), rescue antiemetic (0 ‐ 36 h).
Starting date	February 2015
Contact information	m.cooke@griffith.edu.au
Notes	Rescue antiemetic includes metoclopramide, ondansetron, dexamethasone, droperidol. The trial is registered with the Australian and New Zealand Clinical Trials Registry (ACTRN12614000589684)

PERMALINK

Stimulation of the wrist acupuncture point PC6 for preventing postoperative nausea and vomiting

Anna Lee

Simon KC Chan

Lawrence TY Fan

Abstract

Background

Objectives

Search methods

Selection criteria

Data collection and analysis

Main results

Authors' conclusions

Plain language summary

Summary of findings

Summary of findings for the main comparison. Acupoint PC6 stimulation versus sham for preventing postoperative nausea and vomiting.

Summary of findings 2. Acupoint PC6 stimulation versus antiemetic drug for preventing postoperative nausea and vomiting.

Summary of findings 3. Acupoint PC6 stimulation and antiemetic combination compared to antiemetic for preventing postoperative nausea and vomiting.

Background

Description of the condition

Description of the intervention

How the intervention might work

Why it is important to do this review

Objectives

Methods

Criteria for considering studies for this review

Types of studies

Types of participants

Types of interventions

Types of outcome measures

Primary outcomes

Secondary outcomes

Search methods for identification of studies

Electronic searches

Searching other resources

Data collection and analysis

Selection of studies

Data extraction and management

Assessment of risk of bias in included studies

Measures of treatment effect

Unit of analysis issues

Dealing with missing data

Assessment of heterogeneity

Assessment of reporting biases

Data synthesis

Subgroup analysis and investigation of heterogeneity

Sensitivity analysis

Results

Description of studies

Results of the search

1.

Included studies

Excluded studies

Studies awaiting classification

Ongoing studies

Risk of bias in included studies

2.

3.

Allocation

Blinding

Incomplete outcome data

Selective reporting

Other potential sources of bias

Effects of interventions

PC6 acupoint stimulation versus sham treatment

Primary outcomes

1. Incidence of postoperative nausea

1.1. Analysis.

4.

1. Estimated NNTB for preventing PONV (PC6 acupoint stimulation versus sham).

5.

2. Incidence of postoperative vomiting, defined as either retching or vomiting, or both

1.2. Analysis.

6.

7.

Secondary outcomes

1.Need for rescue antiemetic drug when prophylaxis failed

1.3. Analysis.

2. Adverse effects from PC6 acupoint stimulation and/or antiemetic drug

PC6 acupoint stimulation versus antiemetic drug