Jee 2010.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, combination prophylaxis
Participants	Baseline characteristics Dexamethasone + ondansetron (group O) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 50 Received treatment (n): 50 Analysed (n): 50 Age (mean ± SD, median (IQR), median (range)): 37.1 ± 3.3 Weight (mean ± SD, median (IQR), median (range)): 60.2 ± 8.9 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): 47/3/0/0 Gender (female in %): 100 Non‐smoker (%): 96 History of PONV/motion sickness (%): 24 Type of general anaesthesia: inhalational anaesthesia (sevoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 110.5 Use of perioperative opioids (if yes, which?): fentanyl PCA Type of surgery: gynaecological operation (laparoscopy/laparotomy) Dexamethasone + metoclopramide (group M) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 50 Received treatment (n): 50 Analysed (n): 50 Age (mean ± SD, median (IQR), median (range)): 38.7 ± 3.2 Weight (mean ± SD, median (IQR), median (range)): 61.6 ± 6.8 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): 48/2/0/0 Gender (female in %): 100 Non‐smoker (%): 94 History of PONV/motion sickness (%): 26 Type of general anaesthesia: inhalational anaesthesia (sevoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 118.3 Use of perioperative opioids (if yes, which?): fentanyl PCA Type of surgery: gynaecological operation (laparoscopy/laparotomy) Included criteria: female, adult, ASA I and II, undergoing gynaecological operation with IV‐PCA Excluded criteria: hypersensitivity to metoclopramide, ondansetron or dexamethasone, use of antiemetic drugs, presence of extrapyramidal motor disease, current steroid medication, liver or renal disease, peptic ulcer Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, non‐smoker, history of PONV/motion sickness): no; (perioperative opioids): unclear
Interventions	Intervention characteristics Dexamethasone + ondansetron (group O) Dose: dexamethasone 5 mg, ondansetron 4 mg Time point of administration: dexamethasone after tracheal intubation, ondansetron at end of surgery Route of administration: IV Rescue antiemetics (if yes, which?): ondansetron 1 mg IV Dexamethasone + metoclopramide (group M) Dose: dexamethasone 5 mg, metoclopramide 20 mg Time point of administration: dexamethasone after tracheal intubation, metoclopramide at end of surgery Route of administration: IV Rescue antiemetics (if yes, which?): ondansetron 1 mg IV
Outcomes	Vomiting (6 to 12 hours) Outcome type: dichotomous outcome Arrhythmia (0 to 36 hours) Outcome type: dichotomous outcome Extrapyramidal symptoms (0 to 36 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: Korea Setting: single‐centre, inpatient Author's name: Hea‐Jo Yoon Institution: Department of Anesthesiology and Pain Medicine, Cheil General Hospital and Women Healthcare Center, Kwandong University College of Medicine, Seoul, Korea Email: heajo7890@hanmail.net Address: Cheil General Hospital and Women Healthcare Center, Kwandong University College of Medicine, 1‐19, Mukjeong‐dong, Jung‐gu, Seoul 100‐380, Korea 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)	Low risk	Quote: "using computer generated random numbers"
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
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Judgement comment: no 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: "there were no significant differences in age, body weight, height, ASA, or PONV risk factors between groups (Table 1)" Judgement comment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, non‐smoker, history of PONV/motion sickness): no; (perioperative opioids): unclear