Van Hemelrijck 1991.

Methods	Single‐centre RCT
Participants	Setting: A hospital in Missouri, USA Inclusion criteria: 92 non‐pregnant gynaecologic patients, 19 to 46 years of age, ASA I‐II, scheduled for out‐patient laparoscopic surgery Participant numbers: 92 randomly assigned; 92 analysed
Interventions	Intervention: all patients breathed 100% oxygen for 2 min after receiving a preinduction dose of fentanyl 1.5 μg/kg intravenous and dtubocurarine 3 mg intravenous. Three anaesthetic protocols were used for induction and maintenance of anaesthesia. In protocol 1, anaesthesia was induced with propofol 2.5 mg/kg administered over 2.5 minutes using a syringe‐type infusion pump. After loss of consciousness, succinylcholine 1.5 mg/kg intravenous was administered to facilitate intubation. Anaesthesia was maintained with nitrous oxide 60% and a continuous infusion of propofol at an initial infusion rate of 160 μg/kg/min, which subsequently was titrated within the range of 50 to 200 μg/kg/min. The maintenance infusion rate of propofol was adjusted to maintain an adequate depth of anaesthesia, adjudged by clinical signs and hemodynamic responses. In protocol 2, anaesthesia was induced with propofol 2.5 mg/kg administered over 2.5 minutes using a syringe‐type infusion pump. After loss of consciousness, succinylcholine 1.5 mg/kg intravenous was administered to facilitate intubation. Anaesthesia was maintained with desflurane 4 to 7% inspired concentration in combination with 60% nitrous oxide. The inspired desflurane concentration were adjusted to maintain an adequate depth of anaesthesia, adjudged by clinical signs and hemodynamic responses. In protocol 3, anaesthesia was induced by inhalation of desflurane with nitrous oxide 60% in oxygen. After loss of consciousness, succinylcholine 1.5 mg/kg intravenous was administered to facilitate intubation. Anaesthesia was maintained with desflurane 4 to 7% inspired concentration in combination with 60% nitrous oxide. The inspired desflurane concentration were adjusted to maintain an adequate depth of anaesthesia, adjudged by clinical signs and hemodynamic responses. Control: anaesthesia was induced by inhalation of desflurane with 100% oxygen. After loss of consciousness, succinylcholine 1.5 mg/kg intravenous was administered to facilitate intubation. Anaesthesia was maintained with desflurane 4 to 7% inspired concentration in combination with 100% oxygen. The inspired desflurane concentration were adjusted to maintain an adequate depth of anaesthesia, adjudged by clinical signs and hemodynamic responses.
Outcomes	Secondary outcomes: Severe nausea and vomiting: persistent nausea with repeated episodes of vomiting, requiring treatment
Notes	—
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	High risk	Quote: "The study used an open (non blinded) design."
Blinding of outcome assessment (detection bias) Inhospital case fatality rate/length of stay	Unclear risk	—
Blinding of outcome assessment (detection bias) Complications	Low risk	Quote: "The outcome was assessed by research nurse who was blinded to as to the anaesthetic treatment."
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data.
Selective reporting (reporting bias)	Low risk	All outcomes described in methods section reported.
Other bias	High risk	Fewer than 50 participants per arm.