Sengupta 1988.

Methods	Single‐centre RCT
Participants	Setting: a hospital in London, UK Inclusion criteria: 80 ASA I‐II patients older than 18 years undergoing a standard anaesthetic technique for day‐case laparoscopy Exclusion criteria: patients with a history of excessive nausea and vomiting after previous anaesthetics Participant numbers: 80 randomly assigned; 64 analysed
Interventions	Intervention: patients were given fentanyl 1.5 μg/kg intravenous and anaesthesia was induced with propofol 2 mg/kg intravenous followed by vecuronium 0.06 mg/kg intravenous. The patients received an inspired gas mixture of 33% nitrous oxide and 1% enflurane in oxygen. Control: patients were given fentanyl 1.5 μg/kg intravenous and anaesthesia was induced with propofol 2 mg/kg intravenous followed by vecuronium 0.06 mg/kg intravenous. The patients received an inspired gas mixture of 1% enflurane in oxygen.
Outcomes	Secondary outcomes: Severe nausea and vomiting: patient rated
Notes	16 patients had not returned questionnaires
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Described as randomized but no further details.
Allocation concealment (selection bias)	Unclear risk	No details given.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	This was not reported.
Blinding of outcome assessment (detection bias) Inhospital case fatality rate/length of stay	Unclear risk	—
Blinding of outcome assessment (detection bias) Complications	Unclear risk	This was not reported.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient information.
Selective reporting (reporting bias)	Low risk	All outcomes described in methods section reported.
Other bias	High risk	Fewer than 50 participants per arm.