Lindekaer 1995.

Methods	Study design: Randomized controlled trial Study grouping: Parallel group
Participants	Baseline Characteristics Nitrous oxide‐free – A Number randomized: 21 Number analysed: 21 Age (mean): 44 (± 12.2) % male: 90.5 Type of surgery: Inguinal herniotomy Nitrous oxide‐based – A Number randomized: 21 Number analysed: 21 Age (mean): 47 (± 10.6) % male: 95.2 Type of surgery: Inguinal herniotomy Included criteria: aged 18 ‐ 60 years, ASA 1 or 2, scheduled for day‐case inguinal herniotomy Excluded criteria: NR
Interventions	Intervention Characteristics Nitrous oxide‐free – A Name: Propofol + air Induction: Alfentanil 15 mcg/kg and propofol 2 mg/kg IV followed by alfentanil 45 mcg/kg/hr and propofol 10 mg/kg/hr. Tracheal intubation was facilitated by vecuronium 85 mcg/kg Maintenance: Separate infusions of alfentanil 45 mcg/kg/hr and propofol 10 mg/kg/hr participant's lungs were manually ventilated with air/O₂. FiO₂ 30%. Propofol infusion was continued for 5 mins then reduced to a minimum rate judged clinically on the signs of ‘light’ anaesthesia: movement, lacrimation, sweating, arrhythmia,tachycardia, increasing arterial blood pressure compared to baseline measurements. If necessary, boluses of propofol (20 mg) could be administered Recovery: Alfentanil and propofol infusions were stopped at fascia and skin closure respectively. After skin closure the participant's lungs were ventilated with oxygen only and muscle relaxation was reversed with atropine and neostigmine Other drugs used: Premedication: Diazepam 0.15 mg/kg by mouth and naproxen 1 g per rectum 30 mins before operation Duration of infusion: Min 68 (± 19.1), mean maintenance propofol 0.088 mg/kg/min Nitrous oxide‐based – A Name: Propofol + N₂O Induction: Alfentanil 15 mcg/kg and propofol 2 mg/kg/hr IV followed by alfentanil 45 mcg/kg/hr and propofol 10 mg/kg/hr. Tracheal intubation was facilitated by vecuronium 85 mcg/kg Maintenance: separate infusions of alfentanil 45 mcg/kg/hr and propofol 10 mg/kg/hr participant's lungs were manually ventilated with N₂O/O₂ with a FiO₂ of 0.30. Propofol infusion was continued for 5 mins then reduced to a minimum rate judged clinically on the signs of ‘light’ anaesthesia: movement, lacrimation, sweating, arrhythmia, tachycardia, increasing arterial blood pressure compared to baseline measurements. If necessary, boluses of propofol (20 mg) could be administered Recovery: The alfentanil and propofol infusions were stopped at fascia and skin closure respectively. After skin closure the participant's lungs were ventilated with oxygen only and muscle relaxation was reversed with atropine and neostigmine Other drugs used: Premedication: Diazepam 0.15 mg/kg‐1 by mouth and naproxen 1g per rectum 30 mins before operation Duration of infusion: Min 66 (± 19.3) mean maintenance propofol 0.084 mg/kg/min Monitoring: The propofol infusion was continued for 5 mins at this rate; it was then reduced to a minimum rate judged clinically on the signs of ‘light’ anaesthesia: movement, lacrimation, sweating, arrhythmia, tachycardia, increasing arterial blood pressure compared to baseline measurements. If necessary, boluses of propofol (20 mg) could be administered and these were recorded
Outcomes	Accidental awareness "Before discharge from hospital the anaesthetist questioned the patients about possible awareness during the operation or any dreams." "Two hours after propofol all the patients felt well; none had any unpleasant recollection of events during anaesthesia but one patient reported pleasant dreams"
Identification	Country: Denmark Setting: University hospital Authors name: AL Lindekaer Institution: University of Copenhagen Email: NR Address: AL Lindekrer, Virumvej 104 B, 2830 Virum, Denmark
Aim of study	To evaluate the influence of N₂O on the infusion rate of propofol, allowing anaesthetic depth, as evaluated clinically, to determine the infusion rate
Notes	Sponsorship source: "We thank AGA for their support of the study"
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "by random allocation" Comment: No further details
Allocation concealment (selection bias)	Unclear risk	Quote: "by random allocation" Comment: No further details
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "nurse, who was not involved in adjusting the propofol infusion rate, adjusted the flowmeters for both groups to give an inspired oxygen fraction (FiO₂) of 0.30." Quote: "double blind design" Comment: States double‐blind but does not say who was blinded
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Quote: "double blind design" Quote: "anaesthetist questioned the patients about possible awareness during the operation or any dreams" Comment: Described as double‐bind but no details of who was blinded. Anaesthetist, who presumably was not blinded, asked about awareness
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: No apparent attrition
Selective reporting (reporting bias)	Low risk	Comment: All relevant outcomes described in Methods reported
Other bias	Low risk	Comment: None identified