Feo 2006.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, monoprophylaxis
Participants	Baseline characteristics Dexamethasone Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 49 Received treatment (n): 49 Analysed (n): 49 Age (mean ± SD, median (IQR), median (range)): NA Weight (mean ± SD, median (IQR), median (range)): NA BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA Gender (female in %): NA Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: inhalational anaesthesia (sevoflurane) Duration of anaesthesia or surgery (in min; as mean or median): NA Use of perioperative opioids (if yes, which?): fentanyl 3 μg/kg to 4 μg/kg for induction, mean dose of fentanyl during surgery 10.5 ± 3.3 μg/kg Type of surgery: laparoscopic cholecystectomy Placebo Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 52 Received treatment (n): 52 Analysed (n): 52 Age (mean ± SD, median (IQR), median (range)): NA Weight (mean ± SD, median (IQR), median (range)): NA BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA Gender (female in %): NA Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: inhalational anaesthesia (sevoflurane) Duration of anaesthesia or surgery (in min; as mean or median): NA Use of perioperative opioids (if yes, which?): fentanyl 3 μg/kg to 4 μg/kg for induction, mean dose of fentanyl during surgery 10.5 ± 3.3 μg/kg Type of surgery: laparoscopic cholecystectomy Included criteria: patients undergoing elective laparoscopic cholecystectomy Excluded criteria: ASA IV; age over 75 years; body mass index > 30; pregnancy; signs of endocrine, renal, hepatic, or immunological disease; use of opioids or tranquillizers less than 1 week before the operation; treatment with steroids; history of alcohol or drug abuse; preoperative diagnosis of gallbladder empyema; previous endoscopic sphincterotomy for common bile duct stones Pretreatment: baseline characteristics (age, weight, ASA): unclear (data not shown). Potential effect modifiers (gender, duration of anaesthesia, non‐smoker, history of PONV/motion sickness, perioperative opioids): unclear (data not shown)
Interventions	Intervention characteristics Dexamethasone Dose: 8 mg Time point of administration: 90 minutes before skin incision Route of administration: IV Rescue antiemetics (if yes, which?): ondansetron 4 mg; 10% Placebo group Dose: saline Time point of administration: 90 minutes before skin incision Route of administration: IV Rescue antiemetics (if yes, which?): ondansetron 4 mg; 44%
Outcomes	Vomiting (0 to 24 hours) Outcome type: dichotomous outcome Nausea (0 to 24 hours) or PONV Outcome type: dichotomous outcome Postoperative wound infection (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: Italy Setting: single‐centre Author's name: C.V. Feo Institution: Sezione di Chirurgia Generale, Azienda Ospedaliera Universitaria di Ferrara, Italy Email: cvfeo@unife.it Address: Sezione di Chirurgia Generale, Azienda Ospedaliera Universitaria di Ferrara, Corso Giovecca 203, 44100 Ferrara, Italy Duration of study: March to December 2004 Language: English Study's primary outcome: degree of postoperative nausea and vomiting Trial registry number: NA
Notes	None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "were randomized to receive..." Judgement comment: 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	Quote: "both the patients and the data collector were blinded with respect to the study group" Judgement comment: no information about blinding of anaesthesiologists provided
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "both the patients and the data collector were blinded with respect to the study group"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "six patients (6 per cent) were excluded from the study because of preoperative treatment with steroids (two patients) and previous endoscopic sphincterotomy (four patients)"
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 was no difference in sex distribution, age, body mass index, ASA score, pathology, or median operation and anaesthesia times between the dexamethasone and placebo groups" Judgement comment: baseline characteristics (age, weight, ASA): unclear (data not shown). Potential effect modifiers (gender, duration of anaesthesia, non‐smoker, history of PONV/motion sickness, perioperative opioids): unclear (data not shown)