Gan 2004.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, monoprophylaxis
Participants	Baseline characteristics Ondansetron Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 26 Received treatment (n): NA Analysed (n): 25 Age (mean ± SD, median (IQR), median (range)): 47 ± 10 Weight (mean ± SD, median (IQR), median (range)): 74 ± 18 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): 6/16/3/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): 36 Type of general anaesthesia: inhalational anaesthesia (isoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 199 Use of perioperative opioids (if yes, which?): 343 µg fentanyl intraoperative, 76 µg postoperative fentanyl Type of surgery: major breast surgery Placebo Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 25 Received treatment (n): NA Analysed (n): 24 Age (mean ± SD, median (IQR), median (range)): 46 ± 12 Weight (mean ± SD, median (IQR), median (range)): 77 ± 17 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): 7/16/1 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): 46 Type of general anaesthesia: inhalational anaesthesia (isoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 222 Use of perioperative opioids (if yes, which?): 376 µg fentanyl intraoperative, 91 µg postoperative fentanyl Type of surgery: major breast surgery Included criteria: undergoing major breast surgery Excluded criteria: pregnant, experiencing menstrual symptoms, using a permanent cardiac pacemaker, had previous experience with acupuncture therapies, had received any antiemetic medication or had experienced nausea, vomiting, or retching within 24 hours of surgery Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, history of PONV/motion sickness, perioperative opioids): no; (non‐smoker): unclear
Interventions	Intervention characteristics Ondansetron Dose: 4 mg Time point of administration: at induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): dexamethasone 8 mg; 28% Placebo Dose: saline Time point of administration: at induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): dexamethasone 8 mg; 54%
Outcomes	Vomiting (0 to 2 hours) Outcome type: dichotomous outcome Vomiting (2 to 24 hours) Outcome type: dichotomous outcome Adverse events (general notes in the publication, 24 hours' observation) Outcome type: general notes on side effects
Identification	Sponsorship source: NA Country: USA Setting: outpatient, single‐centre Author's name: Tong J. Gan Institution: Departments of Anesthesiology and Plastic Surgery, Duke University Medical Center, Durham, North Carolina, USA Email: gan00001@mc.duke.edu Address: Department of Anesthesiology, Duke University Medical Center, Box 3094, Durham, NC 2771, USA Duration of study: NA Language: English Study's primary outcome: incidence of nausea Trial registry number: NA
Notes	Two out of 3 groups relevant (electro‐acupoint stimulation)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "randomization was achieved using a random number generator"
Allocation concealment (selection bias)	Unclear risk	Quote: "in a sealed envelope technique..." Judgement comment: not stated; "sequentially numbered, opaque, and sealed envelopes" (SNOSE)
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "the anesthesiologists and care providers were blinded to the study"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "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	Quote: "seventy‐seven patients were enrolled in the study. One patient from the O group did not have her scheduled surgery and one patient from the P group withdrew from participation before the administration of study procedure. Seventy‐five patients completed the study"
Selective reporting (reporting bias)	Unclear risk	Judgement comment: no reference to a study protocol or trial registry number reported
Other bias	Unclear risk	Quote: "there was no difference in patient demographics among the groups..." Judgement comment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, history of PONV/motion sickness, perioperative opioids): no; (non‐smoker): unclear