Huang 2016.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, monoprophylaxis and combination prophylaxis
Participants	Baseline characteristics Ondansetron (group 2) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 21 Received treatment (n): NA Analysed (n): 20 Age (mean ± SD, median (IQR), median (range)): 39.7 ± 5.5 Weight (mean ± SD, median (IQR), median (range)): NA BMI (mean ± SD, median (IQR), median (range)): 22.7 ± 1.2 ASA I/II/III/IV (n): 13/7/0/0 Gender (female in %): NA Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: TIVA (propofol, remifentanil) Duration of anaesthesia or surgery (in min; as mean or median): 52.4 Use of perioperative opioids (if yes, which?): intraoperative remifentanil, 1 patient with postoperative sufentanil 5 µg Type of surgery: laparoscopic cholecystectomy Ondansetron + dexamethasone (group 3) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 22 Received treatment (n): NA Analysed (n): 20 Age (mean ± SD, median (IQR), median (range)): 38.6 ± 8.9 Weight (mean ± SD, median (IQR), median (range)): NA BMI (mean ± SD, median (IQR), median (range)): 22.5 ± 2.0 ASA I/II/III/IV (n): 15/5/0/0 Gender (female in %): NA Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: TIVA (propofol, remifentanil) Duration of anaesthesia or surgery (in min; as mean or median): 54.3 Use of perioperative opioids (if yes, which?): intraoperative remifentanil, 2 patients with postoperative sufentanil 5 µg Type of surgery: laparoscopic cholecystectomy Included criteria: ASA I and II, had undergone laparoscopic cholecystectomy Excluded criteria: systemic cardiovascular or endocrine disease, coagulopathy, needle puncture site infection, BMI > 30, history of chronic pain, hypersensitive or allergic to any medicine Pretreatment: baseline characteristics (age, BMI, ASA): no. Potential effect modifiers (duration of anaesthesia): no; (gender, history of PONV/motion sickness, non‐smoker, perioperative opioids): unclear
Interventions	Intervention characteristics Ondansetron (group 2) Dose: 0.1 mg/kg Time point of administration: end of surgery Route of administration: IV Rescue antiemetics (if yes, which?): NA Ondansetron + dexamethasone (group 3) Dose: ondansetron 0.1 mg/kg, dexamethasone 10 mg Time point of administration: ondansetron end of surgery, dexamethasone after intubation Route of administration: ondansetron IV, dexamethasone perineural Rescue antiemetics (if yes, which?): NA
Outcomes	Vomiting (0 to 24 hours) Outcome type: dichotomous outcome Nausea (0 to 24 hours) Outcome type: dichotomous outcome Sedation/drowsiness (0 to 24 hours) Outcome type: dichotomous outcome
Identification	Sponsorship source: none Country: China Setting: inpatient, single‐centre Author's name: Shuan‐Ke Wang Institution: Department of Anesthesiology and Department of Orthopedics, Second Hospital of Lanzhou University, Lanzhou 730030, China Email: wsk2zzy@126.com Address: Department of Orthopedics, Second Hospital of Lanzhou University, Lanzhou 730030, China Duration of study: November 2013 to April 2014 Language: English Study's primary outcome: effect of intervention on time of first request for additional analgesics Trial registry number: NA
Notes	Two out of 3 groups relevant (without TAP block)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "were randomly divided" Judgement comment: no further information on sequence generation provided
Allocation concealment (selection bias)	Unclear risk	Judgement comment: no statement
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "patients and postoperative assessors were blinded to the intervention protocol, while members of anesthesia and operation groups were not blinded"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "postoperative assessors were blinded to the intervention protocol"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "...was considered statistically significant. In 65 patients initially enrolled, 5 were excluded: 2 patients in group I and 1 patient in group III were converted to open cholecystectomy"
Selective reporting (reporting bias)	Unclear risk	Judgement comment: no reference to a study protocol or trial registry number reported
Other bias	Unclear risk	Quote: "the patients in all groups were comparable in age, BMI and operative time (Table 1)" Judgement comment: baseline characteristics (age, BMI, ASA): no. Potential effect modifiers (duration of anaesthesia): no; (gender, history of PONV/motion sickness, non‐smoker, perioperative opioids): unclear