Mathiesen 2009.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, monoprophylaxis
Participants	Baseline characteristics Placebo (group B) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 43 Received treatment (n): NA Analysed (n): 39 Age (mean ± SD, median (IQR), median (range)): 46 (43 to 50) Weight (mean ± SD, median (IQR), median (range)): 67 (61 to 74) BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: TIVA Duration of anaesthesia or surgery (in min; as mean or median): 75 Use of perioperative opioids (if yes, which?): 3300 µg remifentanil, 40 mg morphine via PCA Type of surgery: abdominal hysterectomy ± salpingo‐oophorectomy Dexamethasone (group C) Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 42 Received treatment (n): NA Analysed (n): 37 Age (mean ± SD, median (IQR), median (range)): 46 (42 to 51) Weight (mean ± SD, median (IQR), median (range)): 67 (61 to 71) BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: TIVA Duration of anaesthesia or surgery (in min; as mean or median): 67 Use of perioperative opioids (if yes, which?): 3018 µg remifentanil, 38 mg morphine via PCA Type of surgery: abdominal hysterectomy ± salpingo‐oophorectomy Included criteria: scheduled for abdominal hysterectomy (salpingo‐oophorectomy), 18 to 75 years of age, BMI 18 to 32, ASA I or II Excluded criteria: inability to cooperate, allergy to any drugs in the study, diagnosis of ovarian cancer, alcohol and/or drug abuse, treatment with antacids or antidepressants, history of diabetes or epilepsy, daily intake of analgesics or intake of any analgesic within 24 hours before surgery, treatment with systemic glucocorticoids within 4 weeks before surgery, known impaired kidney function Pretreatment: baseline characteristics (age, ASA, weight): no. Potential effect modifiers (gender, duration of anaesthesia, perioperative opioids): no; (history of PONV/motion sickness, non‐smoker): unclear
Interventions	Intervention characteristics Placebo (group B) Dose: placebo Time point of administration: before induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): 78.95% (ondansetron 4 mg + 1 mg supplemental doses IV) Dexamethasone (group C) Dose: 8 mg Time point of administration: before induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): 62.16% (ondansetron 4 mg + 1 mg supplemental doses IV)
Outcomes	Vomiting (0 to 24 hours) Outcome type: dichotomous outcome Sedation/drowsiness (0 to 2 hours, 2 to 4 hours, 4 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: Astra Tech, Taastrup, Denmark: Supplier of CADD‐Legacy PCA devices. Conflict of interest: Dr Dahl has received an unrestricted research grant from Pfizer, Denmark Country: Denmark Setting: inpatient, multi‐centre (2) Author's name: Ole Mathiesen Institution: Department of Anaesthesia, Copenhagen University Hospital, Glostrup, Denmark Email: olemat@dadlnet.dk Address: Department of Anaesthesia, Copenhagen University Hospital, Ndr. Ringvej, DK‐2600 Glostrup, Denmark Duration of study: June 2005 to November 2007 Language: English Study's primary outcome: patient‐controlled morphine consumption from 0 to 4 to 0 to 24 hours after operation Trial registry number: NCT00209495
Notes	Two out of 3 groups relevant
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "according to a computer‐generated block randomization schedule prepared by the hospital pharmacy"
Allocation concealment (selection bias)	Low risk	Quote: "study medication was prepared by the hospital pharmacy into identical capsules of either 300 mg pregabalin or placebo. A separate package containing either dexamethasone or isotonic sodium chloride was opened and prepared into a neutral syringe by a nurse, who was not part..." Quote: "...of the study or any handling of the patient. All medications were given to the patient by one of the investigators. Study medication was marked with the name of the project, the investigator’s name and consecutive numbers according to a computer‐generated block randomization schedule prepared by the hospital pharmacy..."
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "no person was aware of group assignment until all patients had been included and assessments were completed"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "no person was aware of group assignment until all patients had been included and assessments were completed"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "...for inclusion in the study. One hundred and twenty‐eight patients, aged 30 to 70 years, were included (Regional Hospital Herning: n 5 80, and Glostrup Hospital: n 5 48) and randomly assigned to their treatment group. However, 12 of these patients were subsequently excluded, resulting in data from 116 patients in the final analyses (Fig. 1). For seven of these patients, we only have data for the first 4 h postoperatively: four patients were re‐operated and were excluded from further analyses, two patients wanted to drop out and have different analgesic medication (NSAID) and one patient’s 24‐h data were not obtained because of logistic problems. There were no significant differences..."
Selective reporting (reporting bias)	Unclear risk	Judgement comment: NCT00209495 (retrospective registration)
Other bias	Unclear risk	Judgement comment: baseline characteristics (age, ASA, weight): no. Potential effect modifiers (gender, duration of anaesthesia, perioperative opioids): no; (history of PONV/motion sickness, non‐smoker): unclear