Yilmazlar 1996.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 3 groups, monoprophylaxis
Participants	Baseline characteristics Placebo Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 20 Received treatment (n): NA Analysed (n): 20 Age (mean ± SD, median (IQR), median (range)): 42.5 ± 3.2 Weight (mean ± SD, median (IQR), median (range)): NA BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 80 Non‐smoker (%): NA History of PONV/motion sickness (%): 0/NA Type of general anaesthesia: inhalational anaesthesia (halothane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): NA Use of perioperative opioids (if yes, which?): intraoperative fentanyl 50 µg to 75 µg IV Type of surgery: thyroidectomy Metoclopramide Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 20 Received treatment (n): NA Analysed (n): 20 Age (mean ± SD, median (IQR), median (range)): 43.2 ± 4.1 Weight (mean ± SD, median (IQR), median (range)): NA BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 80 Non‐smoker (%): NA History of PONV/motion sickness (%): 0/NA Type of general anaesthesia: inhalational anaesthesia (halothane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): NA Use of perioperative opioids (if yes, which?): intraoperative fentanyl 50 µg to 75 µg IV Type of surgery: thyroidectomy Tropisetron Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 20 Received treatment (n): NA Analysed (n): 20 Age (mean ± SD, median (IQR), median (range)): 41.1 ± 2.8 Weight (mean ± SD, median (IQR), median (range)): NA BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 85 Non‐smoker (%): NA History of PONV/motion sickness (%): 0/NA Type of general anaesthesia: inhalational anaesthesia (halothane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): NA Use of perioperative opioids (if yes, which?): intraoperative fentanyl 50 µg to 75 µg IV Type of surgery: thyroidectomy Included criteria: ASA I or II, 22 to 60 years of age, scheduled for thyroidectomy with postoperative bed rest of at least 24 hours Excluded criteria: nausea or emesis in the preoperative period, history of postoperative vomiting after previous anaesthesia, ASA III and IV Pretreatment: baseline characteristics (age, ASA): no; (weight): unclear. Potential effect modifiers (gender, history of PONV): no; (history of motion sickness, duration of anaesthesia, non‐smoker, perioperative opioids): unclear
Interventions	Intervention characteristics Placebo Dose: saline Time point of administration: during anaesthesia induction Route of administration: IV Rescue antiemetics (if yes, which?): not defined Metoclopramide Dose: 0.2 mg/kg Time point of administration: during anaesthesia induction Route of administration: IV Rescue antiemetics (if yes, which?): not defined Tropisetron Dose: 5 mg Time point of administration: during anaesthesia induction Route of administration: IV Rescue antiemetics (if yes, which?): not defined
Outcomes	Vomiting (0 to 2 hours) Outcome type: dichotomous outcome
Identification	Sponsorship source: NA Country: Turkey Setting: inpatient, single‐centre Author's name: A. Yilmazlar Institution: Department of Anaesthesiology, Uludag University School of Medicine, Bursa, Turkey Email: NA Address: Department of Anaesthesiology, Uludag University School of Medicine, Corukle 16059, Bursa, Turkey Language: English Duration of study: NA Trial registry number: NA Study's primary outcome: NA
Notes	None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "randomized" Judgement comment: insufficient information about the sequence generation process
Allocation concealment (selection bias)	Unclear risk	Judgement comment: no statement
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Judgement comment: "double‐blind". No further statement
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Judgement comment: "double‐blind". No further statement
Incomplete outcome data (attrition bias) All outcomes	Low risk	Judgement comment: no missing outcome data
Selective reporting (reporting bias)	Unclear risk	Judgement comment: no reference to a study protocol or trial registry number reported
Other bias	Unclear risk	Quote: "Table 1 summarizes the demographic data of the three groups, which were comparable with regard to age and sex. The three groups were not significantly different (P> 0.05). The number of patients vomiting..." Judgement comment: baseline characteristics (age, ASA): no; (weight): unclear. Potential effect modifiers (gender, history of PONV): no; (history of motion sickness, duration of anaesthesia, non‐smoker, perioperative opioids): unclear