Areeruk 2016.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, monoprophylaxis
Participants	Baseline characteristics Dexamethasone (group D) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): NA Received treatment (n): NA Analysed (n): 25 Age (mean ± SD, median (IQR), median (range)): 43.40 ± 9.28 Weight (mean ± SD, median (IQR), median (range)): 55.65 ± 10.15 BMI (mean ± SD, median (IQR), median (range)): 22.99 ± 4.23 ASA I/II/III/IV (n): 11/14/0/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: inhalational anaesthesia (sevoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 142.20 Use of perioperative opioids (if yes, which?): fentanyl 0.5 µg/kg for induction, intraoperative morphine 0.1 mg/kg, postoperatively morphine via PCA at 24 hours (15.88mg) Type of surgery: gynaecological laparotomy surgery Placebo (group P) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): NA Received treatment (n): NA Analysed (n): 24 Age (mean ± SD, median (IQR), median (range)): 41.67 ± 10.05 Weight (mean ± SD, median (IQR), median (range)): 56.49 ± 8.84 BMI (mean ± SD, median (IQR), median (range)): 23.50 ± 3.47 ASA I/II/III/IV (n): 12/12/0/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: inhalational anaesthesia (sevoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 120.83 Use of perioperative opioids (if yes, which?): fentanyl 0.5 µg/kg for induction, intraoperative morphine 0.1 mg/kg, postoperative morphine via PCA at 24 hours (24.25 mg) Type of surgery: gynaecological laparotomy surgery Included criteria: ASA I or II, 18 to 65 years of age, undergoing elective gynaecological laparotomy surgery with Pfannenstiel incision under general anaesthesia consented to participate in the study Excluded criteria: patients with diabetic mellitus, treatment with steroids, obesity, use of opioid or analgesic drug within 1 month before the study, history of alcohol or drug abuse, pregnancy, undergoing surgical staging surgery, history of chronic pain, history of peptic ulcer or gastritis, those who refused the study Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender): no; (history of PONV/motion sickness, non‐smoker): unclear; (perioperative opioids, duration of anaesthesia ‐> significant P values): yes
Interventions	Intervention characteristics Dexamethasone (group D) Dose: 8 mg Time point of administration: after intubation Route of administration: IV Rescue antiemetics (if yes, which?): NA Placebo (group P) Dose: saline Time point of administration: after intubation Route of administration: IV Rescue antiemetics (if yes, which?): NA
Outcomes	Postoperative wound infection (0 to 7 days) Outcome type: dichotomous outcome
Identification	Sponsorship source: NA Country: Thailand Setting: inpatient, single‐centre Author's name: Pornpatra Areeruk Institution: Department of Anesthesiology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand Email: pornpatra.are@mahidol.ac.th Address: Department of Anesthesiology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand Duration of study: NA Language: English Study's primary outcome: total morphine consumption at six hours and 24 hours postoperatively Trial registry number: TCTR20151116001
Notes	None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "based on computer generated random number list (nQuery program)"
Allocation concealment (selection bias)	Unclear risk	Quote: "the study solution was prepared by a nurse not involved in the perioperative and postoperative care of the patient three hours before surgery. Then it was given to the patient in a sealed envelope, which was handed over to the anesthesiologist who was not involved in the study" Judgement comment: not mentioned: opaque, sequentially numbered envelopes (SNOSE)
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "patients, anesthesiologists, and the follow‐up team were blinded to the administered drugs"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "all patients, anesthesiologists, and the follow‐up team were blinded to the administered drugs"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "fifty‐two patients undergoing gynecological laparotomy surgery were recruited. Three patients were excluded due to receiving succinylcholine for induction, operative time more than three hours, and having paracoxib for pain relief in the postanesthesia care unit"
Selective reporting (reporting bias)	Unclear risk	Judgement comment: TCTR20151116001 (retrospective registration)
Other bias	High risk	Judgement comment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender): no; (history of PONV/motion sickness, non‐smoker): unclear; (perioperative opioids, duration of anaesthesia ‐> significant P values): yes