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.