Perez Ascencio 1992.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 4 groups, monoprophylaxis
Participants	Baseline characteristics Droperidol Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 15 Received treatment (n): NA Analysed (n): 15 Age (mean ± SD, median (IQR), median (range)): 28 ± 7 Weight (mean ± SD, median (IQR), median (range)): 58 ± 6 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): NA Non‐smoker (%): NA History of PONV/motion sickness (%): 0/NA Type of general anaesthesia: balanced general anaesthesia (enflurane, fentanyl) Duration of anaesthesia or surgery (in min; as mean or median): 207 Use of perioperative opioids (if yes, which?): 359 µg fentanyl intraoperative Type of surgery: head and neck surgery Diphenidol Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 15 Received treatment (n): NA Analysed (n): 15 Age (mean ± SD, median (IQR), median (range)): 27 ± 9 Weight (mean ± SD, median (IQR), median (range)): 59 ± 7 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): NA Non‐smoker (%): NA History of PONV/motion sickness (%): 0/NA Type of general anaesthesia: balanced general anaesthesia (enflurane, fentanyl) Duration of anaesthesia or surgery (in min; as mean or median): 192 Use of perioperative opioids (if yes, which?): 303 µg fentanyl intraoperative Type of surgery: head and neck surgery Metoclopramide Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 15 Received treatment (n): NA Analysed (n): 15 Age (mean ± SD, median (IQR), median (range)): 29 ± 14 Weight (mean ± SD, median (IQR), median (range)): 62 ± 10 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): NA Non‐smoker (%): NA History of PONV/motion sickness (%): 0/NA Type of general anaesthesia: balanced general anaesthesia (enflurane, fentanyl) Duration of anaesthesia or surgery (in min; as mean or median): 249 Use of perioperative opioids (if yes, which?): 456 µg fentanyl intraoperative Type of surgery: head and neck surgery Placebo Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 15 Received treatment (n): NA Analysed (n): 15 Age (mean ± SD, median (IQR), median (range)): 30 ± 11 Weight (mean ± SD, median (IQR), median (range)): 61 ± 8 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): NA Non‐smoker (%): NA History of PONV/motion sickness (%): 0/NA Type of general anaesthesia: balanced general anaesthesia (enflurane, fentanyl) Duration of anaesthesia or surgery (in min; as mean or median): 155 Use of perioperative opioids (if yes, which?): 340 µg fentanyl intraoperative Type of surgery: head and neck surgery Included criteria: both sexes, 18 to 60 years of age, scheduled for elective surgery of the head and neck (maxillofacial surgery, plastic surgery, reconstructive surgery), ASA I or II Excluded criteria: old history of nausea and postoperative vomiting, obese, women, pregnant or in the menstrual period, pathology leading to vomiting Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (history of PONV): no; (gender, non‐smoker, history of motion sickness): unclear; (perioperative opioids, duration of anaesthesia): yes
Interventions	Intervention characteristics Droperidol Dose: 15 µg/kg to 20 µg/kg Time point of administration: 30 minutes before end of anaesthetic procedure Route of administration: IV Rescue antiemetics (if yes, which?): NA Diphenidol Dose: 150 µg/kg Time point of administration: 30 minutes before end of anaesthetic procedure Route of administration: IV Rescue antiemetics (if yes, which?): NA Metoclopramide Dose: 150 µg/kg Time point of administration: 30 minutes before end of anaesthetic procedure Route of administration: IV Rescue antiemetics (if yes, which?): NA Placebo Dose: 3 ml saline Time point of administration: 30 minutes before end of anaesthetic procedure Route of administration: IV Rescue antiemetics (if yes, which?): NA
Outcomes	Vomiting (0 to 4 hours) Outcome type: dichotomous outcome
Identification	Sponsorship source: NA Country: Mexico Setting: inpatient, single‐centre Author's name: Rebeca E. Pérez‐Ascencio Institution: Departemento de Anestesiología del Hospital de Escpecialidades del Centro Médico La Raza Email: NA Address: Departemento de Anestesiología del Hospital de Escpecialidades del Centro Médico La Raza, Instituto Mexicano del Seguro social (IMSS), México D.F. Duration of study: NA Language: Spanish (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: "a random population of 60 patients ..." (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: no statement on blinding of participants and personnel
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Judgement comment: no statement on blinding of outcome assessor
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	High risk	Judgement comment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (history of PONV): no; (gender, non‐smoker, history of motion sickness): unclear; (perioperative opioids, duration of anaesthesia): yes