Amir 2007.

Methods	Parallel‐group randomized trial, conducted in India. Study dates not reported.
Participants	40 children and adults undergoing middle ear surgery. Exclusion: People with cardiovascular disease, central nervous system problems, previous history of PONV and/or motion sickness, and smokers. No details about withdrawals or loss to follow‐up.
Interventions	Group 1: electro‐acupuncture at frequency of 4 Hz and current intensity increased to a degree just less than what caused discomfort, given 20 min before induction for duration of surgery (n = 20). Group 2: sham electro‐acupuncture. No details given except that participants experienced needle pricks (n = 20).
Outcomes	Nausea (0 ‐ 24 h), vomiting (0 ‐ 24 h), risk of rescue antiemetic drug (0 ‐ 24 h), risk of adverse effects.
Notes	Rescue antiemetic was ondansetron 4 mg IV after first episode of PONV and repeated when necessary at 6‐hourly intervals. No side effects in sham electro‐acupuncture group. Erythema occurred in 3 participants in the electro‐acupuncture 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	"Informed consent was taken from the selected patients and they were divided into two groups of twenty each using 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	"A blinded observed collected postoperative data of PONV".
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data reported for the 20 participants randomized to each group.
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. "Differences in mean age, weight, sex and duration of surgery were statistically insignificant".