Jensen 1993a.

Methods	Single‐centre RCT
Participants	Setting: University Hospital Linköping, Linköping, Sweden Inclusion criteria: patients > 18 years, scheduled for laparoscopic cholecystectomy Participant numbers: 42 randomly assigned; 42 analysed for the outcome of pneumonia; 40 analysed for the outcome of length of hospital stay
Interventions	Intervention: patients received meperidine 1 mg/kg and atropine 6 μg/kg im for premedication approximately 45 min prior to anaesthetic induction. Anaesthesia was induced intravenously with fentanyl 2 μg/kg, and thiopental 4 to 6 mg/kg was administered until loss of eyelash reflex. Tracheal intubation was facilitated by the use of succinylcholine 1 mg/kg after pretreatment with vecuronium 1 mg. The patients received isoflurane with nitrous oxide in oxygen for maintenance of anaesthesia. An inspiratory fraction of oxygen of 0.3 was used. Control: patients received meperidine 1 mg/kg and atropine 6 μg/kg im for premedication approximately 45 min prior to anaesthetic induction. Anaesthesia was induced intravenously with fentanyl 2 μg/kg, and thiopental 4 to 6 mg/kg was administered until loss of eyelash reflex. Tracheal intubation was facilitated by the use of succinylcholine 1 mg/kg after pretreatment with vecuronium 1 mg. The patients received isoflurane with air in oxygen for maintenance of anaesthesia. An inspiratory fraction of oxygen of 0.3 was used.
Outcomes	Secondary outcomes: Pneumonia: no specific definition Length of hospital stay
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	Unclear risk	Described as double‐blind but no further details.
Blinding of outcome assessment (detection bias) Inhospital case fatality rate/length of stay	Low risk	The outcome measurement is not likely to be influenced by lack of blinding.
Blinding of outcome assessment (detection bias) Complications	Low risk	Quote: "Postoperative data was assessed by the postoperative ward staff and surgeon blinded to the anaesthetic technique."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups.
Selective reporting (reporting bias)	Low risk	All outcomes described in methods section reported.
Other bias	High risk	Fewer than 50 participants per arm.