Tarhan 2007.

Study characteristics
Methods	RCT
Participants	88 ASA 1‐2, 20‐38 year old women undergoing elective CS under spinal anaesthesia with no history of GI disease, recent antiemetic use or contraindication for regional anaesthesia.
Interventions	Intervention 1: sedative (Comparison 6) Propofol 20 mg bolus, 1 mg/kg/hour. N = 30. Intervention 2: sedative (Comparison 6) Midazolam 1 mg bolus 1 mg/kg/hour. N = 30. Comparison: placebo Normal saline. N = 28.
Outcomes	Nausea, vomiting, retching ‐ intraoperative and postoperative.
Notes	Setting: Ankara, Turkey. Dates: not reported. Funding source: not reported. Declaration of interest: not reported. Retching combined with vomiting. In Table 2, Column 4, reports that the control group consisted of n = 28, but then in the body of the table, it states n = 30. Email correspondence with author confirms that 28 participants were actually enrolled in the control group. Drugs are in separate subgroups but then pooled in our analysis so the placebo data are dealt with according to our methods (Unit of analysis issues)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated random number list.
Allocation concealment (selection bias)	Low risk	Drugs prepared and covered according to a random number list by a personnel member who was not aware of the study.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "Double blind". No additional information about participant blinding.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Postoperative outcomes assessed by blinded clinician.
Incomplete outcome data (attrition bias) All outcomes	Low risk	None.
Selective reporting (reporting bias)	Unclear risk	We did not assess the trial protocol.
Other bias	Low risk	No baseline differences.