Sadhasivam 1999.

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): 27 Received treatment (n): 27 Analysed (n): 27 Age (mean ± SD, median (IQR), median (range)): 46.5 ± 11.2 Weight (mean ± SD, median (IQR), median (range)): 54.7 ± 10.7 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): 19/8/0/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): 3.70/18.52 Type of general anaesthesia: inhalational anaesthesia (N2O, isoflurane) Duration of anaesthesia or surgery (in min; as mean or median): 147.3 Use of perioperative opioids (if yes, which?): 59.1 mg meperidine Type of surgery: modified radical mastectomy Ondansetron Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 27 Received treatment (n): 27 Analysed (n): 27 Age (mean ± SD, median (IQR), median (range)): 44.9 ± 11.1 Weight (mean ± SD, median (IQR), median (range)): 56.9 ± 8.9 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): 21/6/0/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): 7.41/18.52 Type of general anaesthesia: inhalational anaesthesia (N2O, isoflurane) Duration of anaesthesia or surgery (in min; as mean or median): 157.8 Use of perioperative opioids (if yes, which?): 58.9 mg meperidine Type of surgery: modified radical mastectomy Included criteria: ASA I or II, adult female patients undergoing modified radical mastectomy for carcinoma of the breast Excluded criteria: morbid obesity, gastrointestinal disease with gastric outlet obstruction, had received drugs with an antiemetic effect within 24 hours before anaesthesia Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, history of PONV/motion sickness, perioperative opioids): no; (non‐smoker): unclear
Interventions	Intervention characteristics Placebo Dose: saline Time point of administration: at end of surgery Route of administration: IV Rescue antiemetics (if yes, which?): 59% (150 µg/kg metoclopramide IV, ondansetron 4 mg IV) Ondansetron Dose: 4 mg Time point of administration: at end of surgery Route of administration: IV Rescue antiemetics (if yes, which?): 15% (150 µg/kg metoclopramide IV, ondansetron 4 mg IV)
Outcomes	Vomiting (0 to 24 hours) Outcome type: dichotomous outcome PONV (0 to 24 hours) Outcome type: dichotomous outcome Headache (0 to 24 hours) Outcome type: dichotomous outcome Adverse events (general notes in the publication, 24 hours' observation) Outcome type: general notes on side effects
Identification	Sponsorship source: NA Country: India Setting: inpatient, single‐centre Author's name: Abha Saxena Institution: Department of Anesthesiology, Institute Rotary Cancer Hospital, All India Institute of Medical Sciences, New Delhi, India Email: saxenas@medinst.ernet.in Address: Department of Anesthesiology, Institute Rotary Cancer Hospital, All India Institute of Medical Sciences, New Delhi, India Duration of study: NA Language: English 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	Quote: "patients were allocated to receive, in a randomized, double‐blinded manner, a single dose of either ondansetron 4 mg (4 mL) IV or saline at an equal volume (4 mL) as a placebo at the end of the surgery" Judgement comment: no 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	Quote: "patients were allocated to receive, in a randomized, double‐blinded manner, a single dose of either ondansetron 4 mg (4 mL) IV or saline at an equal volume (4 mL) as a placebo at the end of the surgery" Judgement comment: insufficient information on blinding
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Judgement comment: insufficient information on blinding ("double‐blinded manner")
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: "there were no significant differences between the groups with regard to age, weight, ASA physical status, duration of anesthesia, and intraoperative and postoperative analgesic requirements (Table 1)" Judgement comment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, history of PONV/motion sickness, perioperative opioids): no; (non‐smoker): unclear