Liu 2008.

Methods	Parallel‐group randomized trial, conducted in China. Study conducted from June 2006 to July 2007.
Participants	96 people undergoing laparoscopic cholecystectomy who were aged 18 ‐ 60 years. Exclusions: pregnancy, women experiencing menstrual symptoms, patients with permanent cardiac pace‐maker, previous experience with acupuncture therapies before surgery, received antiemetics or experienced nausea, vomiting, or retching within 24 h of surgery. No participants withdrew from study.
Interventions	Group 1: transcutaneous electro‐acupoint stimulation using a peripheral nerve stimulator at P6 (2 ‐ 100 Hz, 50 ms, 0.5 ‐ 4 mA) applied 30 to 60 min before induction of anaesthesia, and continued to the end of surgery (n = 48). Group 2: inactive device with similar electrode for transcutaneous electro‐acupoint stimulation using a peripheral nerve stimulator at P6 applied 30 ‐ 60 min before induction of anaesthesia, and continued to the end of surgery (n = 48).
Outcomes	Nausea (0 ‐ 24 h), vomiting (0 ‐ 24 h), risk of rescue antiemetic drug (0 ‐ 24 h), adverse effects of transcutaneous electro‐acupoint stimulation.
Notes	Rescue antiemetic drug was ondansetron 4 mg IV, to participants who had a nausea score of > 5 on a 10‐point scale, vomited twice within 15 min, or at the participant's request. P6 acupoint stimulation was associated with a reduction in the risk of severe nausea (Group 1: 2/48 versus Group 2: 14/48). No redness, swelling, itching, and pain, or other relevant complications at P6 acupoint in the 2 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	"Patients were randomized into two groups of 48 in each using a table of random numbers".
Allocation concealment (selection bias)	Unclear risk	Insufficient information.
Blinding of patients (performance bias) All outcomes	Low risk	Authors took adequate steps to make interventions appear similar.
Blinding of healthcare providers (performance bias) All outcomes	Low risk	"The anesthesiologists and care providers were blinded to the study group".
Blinding of outcome assessor (detection bias) All outcomes	Low risk	"Postoperative data were collected by a separate research nurse who was not aware of the preoperative or perioperative management of patients".
Incomplete outcome data (attrition bias) All outcomes	Low risk	"All 96 patients completed the study".
Selective reporting (reporting bias)	Low risk	All expected outcomes reported.
Other bias	Low risk	Baseline characteristics were comparable. "As shown in Tables 1 and 2, the patients' gender, age, weight, ASA physical status, previous PONV history, duration of surgery or anaesthesia, transfusion amount, operative procedure and doses of opioids in the two groups were not significantly different".