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".