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.