Stefani 1995.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 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)): 56.3 ± 12.03 Weight (mean ± SD, median (IQR), median (range)): 72.8 ± 14.66 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: inhalational anaesthesia (N₂O, Isoflurane) Duration of anaesthesia or surgery (in min; as mean or median): 68.5 Use of perioperative opioids (if yes, which?): 1.5 µg/kg fentanyl at induction, ketorolac for postoperative analgesia Type of surgery: laparoscopic cholecystectomy Tropisetron Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 20 Received treatment (n): NA Analysed (n): 20 Age (mean ± SD, median (IQR), median (range)): 50.55 ± 10.31 Weight (mean ± SD, median (IQR), median (range)): 68.95 ± 10.09 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: inhalational anaesthesia (N₂O, Isoflurane) Duration of anaesthesia or surgery (in min; as mean or median): 67.55 Use of perioperative opioids (if yes, which?): 1.5 µg/kg fentanyl at induction, ketorolac for postoperative analgesia Type of surgery: laparoscopic cholecystectomy Included criteria: female, ASA I or II Excluded criteria: NA Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, perioperative opioids): no; (history of PONV/motion sickness, non‐smoker): unclear
Interventions	Intervention characteristics Placebo Dose: saline Time point of administration: 15 minutes before end of surgery Route of administration: IV Rescue antiemetics (if yes, which?): metoclopramide 10 mg IV Tropisetron Dose: 5 mg Time point of administration: 15 minutes before end of surgery Route of administration: IV Rescue antiemetics (if yes, which?): metoclopramide 10 mg IV
Outcomes	Vomiting (0 to 24 hours) Outcome type: dichotomous outcome Nausea (0 to 24 hours) Outcome type: dichotomous outcome
Identification	Sponsorship source: NA Country: Italy Setting: inpatient, single‐centre Author's name: M. Stefani Institution: Servizi di Anestesia e Terapia del Dolore, Ospedale Regina Apostolorum Alabano Laziale, Roma Email: NA Address: NA Duration of study: NA Language: Italian (translated by Insa Backhaus) Study's primary outcome: NA Trial registry number: NA
Notes	None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Judgement comment: quote: "with a randomized double‐blind system, the patients were randomly assigned to two groups of 20 people" (translated). 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	Unclear risk	Judgement comment: insufficient information on blinding ("double‐blind")
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Judgement comment: insufficient information on blinding ("double‐blind")
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	Judgement comment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, perioperative opioids): no; (history of PONV/motion sickness, non‐smoker): unclear