Pedersen 1993.

Methods	Single‐centre RCT
Participants	Setting: Herlev hospital, Herlev, Denmark Inclusion criteria: 44 ASA I‐II patients, aged 30 to 65 years, scheduled for elective abdominal hysterectomy with or without salpingo oophorectomy Exclusion criteria: patients with gastrointestinal disease of any kind, malignancy, or weight < 45 kg or > 90 kg; preoperative medication known to interfere with bowel function; contraindications against any of the anaesthetics used; insertion of a nasogastric tube; surgical complications; administration of laxatives or enemas before the fourth day postoperatively (the operation day being day 0) Participant numbers: 44 randomly assigned; 36 analysed
Interventions	Intervention: diazepam 0.15 mg/kg administered orally 1 h before anaesthesia was used as premedication. Anaesthesia was induced with fentanyl 3 μg/kg and atracurium as precurarization followed by thiopentone 3 to 5 mg/kg. Intubation was facilitated by suxamethonium 1.5 mg/kg. Anaesthesia was maintained with fentanyl 2 μg/kg/h and isoflurane with nitrous oxide in 30% oxygen. Ventilation was adjusted to maintain end‐tidal carbon dioxide tension between 4 and 4.5 kPa. After the disappearance of the effect of suxamethonium, neuromuscular block was achieved with a bolus of atracurium, 0.3 mg/kg, and maintained with infusion of atracurium. Control: diazepam 0.15 mg/kg administered orally 1 h before anaesthesia was used as premedication. Anaesthesia was induced with fentanyl 3 μg/kg and atracurium as precurarization followed by thiopentone 3 to 5 mg/kg. Intubation was facilitated by suxamethonium 1.5 mg/kg. Anaesthesia was maintained with fentanyl 2 μg/kg/h and isoflurane in 30% oxygen. Ventilation was adjusted to maintain end‐tidal carbon dioxide tension between 4 and 4.5 kPa. After the disappearance of the effect of suxamethonium, neuromuscular block was achieved with a bolus of atracurium, 0.3 mg/kg, and maintained with infusion of atracurium.
Outcomes	Secondary outcomes: Severe nausea and vomiting: patient rated
Notes	8 patients were excluded during the study: 3 patients because of per‐ or postoperative surgical complications, 1 patient because of the surgeon's wish for insertion of a nasogastric tube due to distension of the intestines (the patient received nitrous oxide), 3 patients due to erroneous administration of laxative on the second postoperative day and 1 patient because of severe gastrointestinal discomfort on the third day postoperatively requiring an enema (the patient received nitrous oxide).
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	Low risk	Quote: "The mixture of gas administered was blinded for everyone other than the anaesthetist."
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: "Nausea and vomiting were assessed by an investigator other than the anaesthetist or the surgeon."
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.