Arslan 2011.

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): NA Received treatment (n): NA Analysed (n): 30 Age (mean ± SD, median (IQR), median (range)): 42.8 ± 9.9 Weight (mean ± SD, median (IQR), median (range)): 72.8 ± 10.1 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): 24/6/0/0 Gender (female in %): 76.7 Non‐smoker (%): 63.3 History of PONV/motion sickness (%): 0 Type of general anaesthesia: inhalational anaesthesia (sevoflurane, remifentanil) Duration of anaesthesia or surgery (in min; as mean or median): 105.5 Use of perioperative opioids (if yes, which?): intraoperative remifentanil infusion 0.2 µg/kg Type of surgery: laparoscopic cholecystectomy Metoclopramide Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): NA Received treatment (n): NA Analysed (n): 30 Age (mean ± SD, median (IQR), median (range)): 41.5 ± 7.8 Weight (mean ± SD, median (IQR), median (range)): 70.5 ± 8.1 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): 25/5/0/0 Gender (female in %): 83.3 Non‐smoker (%): 70.0 History of PONV/motion sickness (%): 0 Type of general anaesthesia: inhalational anaesthesia (sevoflurane, remifentanil) Duration of anaesthesia or surgery (in min; as mean or median): 110.5 Use of perioperative opioids (if yes, which?): intraoperative remifentanil infusion 0.2 µg /kg Type of surgery: laparoscopic cholecystectomy Included criteria: patients scheduled for laparoscopic cholecystectomy (25 to 55 years of age; 48 women) with an American Society of Anesthesiologists (ASA) physical status classification system risk of I or II Excluded criteria: history of hepatic, renal, or cardiovascular disease; chronic obstructive pulmonary disease; haematological or gastrointestinal disorders, or both; hypersensitivity to propofol or to any other drug; history of vertigo or motion sickness; previous postoperative emesis; pregnant or breastfeeding or menstruating women; use of an antiemetic agent within 24 hours before surgery; laparoscopy replaced by laparotomy 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 Dose: 2 × 8 mg Time point of administration: at induction of anaesthesia and at time to skin closure Route of administration: IV Rescue antiemetics (if yes, which?): 20% (metoclopramide 10 mg) Metoclopramide Dose: 0.2 mg/kg Time point of administration: at time to skin closure (metoclopramide) Route of administration: IV Rescue antiemetics (if yes, which?): 46.7% (metoclopramide 10 mg)
Outcomes	Vomiting (0 to 4 hours) Outcome type: dichotomous outcome Vomiting (4 to 12 hours)) Outcome type: dichotomous outcome PONV (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: Turkey Setting: inpatient, single‐centre Author's name: Mustafa Arslan Institution: Gazi University Faculty of Dentistry, Anesthesiology and Reanimation Specialist, Department of Oral and Maxillofacial Surgery Email: mustarslan@gmail.com Address: Gazi University Faculty of Dentistry, Anesthesiology and Reanimation Specialist, Department of Oral and Maxillofacial Surgery, Emek 06510 Ankara, Turkey Duration of study: NA Language: English Study's primary outcome: primary end point of this study was total PONV rate up to 24 hours post anaesthesia Trial registry number: NA
Notes	None&&
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "using a computer‐generated random number table"
Allocation concealment (selection bias)	Unclear risk	Judgement comment: no statement
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "patients, the anesthesiologist attending during surgery, and the anesthesiologist who collected postoperative data were all blinded to the randomization process and the identity of the study drugs"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "patients, the anesthesiologist attending during surgery, and the anesthesiologist who collected postoperative data were all blinded to the randomization process and the identity of the study drugs"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "a total of 64 patients were approached for study inclusion, 4 of whom were excluded based on criteria described previously"
Selective reporting (reporting bias)	Unclear risk	Judgement comment: no reference to a study protocol or trial registry number reported
Other bias	Unclear risk	Quote: "no statistically significant between‐group differences were found in the patients’ demographic and clinical characteristics" 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