Ngan Kee 2002.

Methods	Study design: Randomized controlled trial Study grouping: Parallel group
Participants	Baseline Characteristics Nitrous oxide‐free – A Number randomized: 20 Number analysed: 20 Age (mean): 35 (range 27 ‐ 43) % male: 0 Type of surgery: Caesarean section Nitrous oxide‐based – A Number randomized: 20 Number analysed: 20 Age (mean): 34 (range 26 ‐ 41) % male: 0 Type of surgery: Caesarean section Nitrous oxide‐based – B Number randomized: 20 Number analysed: 20 Age (mean): 34 (range 27 ‐ 41) % male: 0 Type of surgery: Caesarean section Included criteria: ASA I and II women with term singleton pregnancies having elective Caesarean section under GA Excluded criteria: Pre‐existing or pregnancy‐induced hypertension, cardiovascular or cerebrovascular disease or known foetal abnormalities
Interventions	Intervention Characteristics Nitrous oxide‐free – A Name: Sevoflurane Induction: Pre‐oxygenation rapid sequence induction using thiopental 4 mg/kg and succinylcholine 1.5 mg/kg atracurium as required for further muscle relaxation as indicated by results of peripheral nerve stimulation Maintenance: Lungs ventilated to maintain end‐tidal CO₂ concentration of 4.3 kPa. FiO₂ 1.0 with end‐tidal sevoflurane 2.0%. Circle circuit with a fresh gas flow of 6 l/min was used and for all participants sevoflurane vaporiser was originally set to 6% for the first 60 secs and then adjusted to the required end‐tidal concentration Recovery: Neostigmine and atropine Other drugs used: Ranitidine 150 mg night before surgery 30 ml 0.3 M sodium citrate on arrival at theatre Premedication: NR Duration of anaesthetic (mins): NR Nitrous oxide‐based – A Name: Sevoflurane + Fi N₂O 0.5 Induction: Pre‐oxygenation rapid sequence induction using thiopental 4 mg/kg and succinylcholine 1.5 mg/kg atracurium as required for further muscle relaxation as indicated by results of peripheral nerve stimulation Maintenance: Lungs ventilated to maintain end‐tidal CO₂ concentration of 4.3 kPa. Inspired fractions chosen to give approximately equivalent MAC values in all groups. FiO₂ 0.5 + FiN₂O 0.5 with end‐tidal sevoflurane 1.0%. Circle circuit with a fresh gas flow of 6 l/min was used and for all participants sevoflurane vaporiser was originally set to 6% for the first 60 secs and then adjusted to the required end‐tidal concentration Recovery: Neostigmine and atropine Other drugs used: Ranitidine 150 mg night before surgery 30 ml 0.3 M sodium citrate on arrival at theatre Premedication: NR Duration of anaesthetic (mins): NR Nitrous oxide‐based – B Name: Sevoflurane +Fi N₂O 0.7 Induction: Pre‐oxygenation rapid sequence induction using thiopental 4 mg/kg and succinylcholine 1.5 mg/kg atracurium as required for further muscle relaxation as indicated by results of peripheral nerve stimulation Maintenance: Lungs ventilated to maintain end‐tidal CO₂ conc of 4.3 kPa. FiO₂ 0.3 Fi N₂O 0.7 with end‐tidal sevoflurane 0.6%. Circle circuit with a fresh gas flow of 6 l/min was used and for all participants sevoflurane vaporiser was originally set to 6% for the first 60 secs and then adjusted to the required end‐tidal concentration Recovery: Neostigmine and atropine Other drugs used: Ranitidine 150 mg night before surgery 30 ml 0.3 M sodium citrate on arrival at theatre Premedication: NR Duration of anaesthetic (mins): NR Monitoring: Anaesthetics in different groups aimed to give same overall MAC. Anaesthetic concentration adjusted to maintain allocated end‐tidal concentration. No mention of adjusting anaesthetic concentration according to participant's response or haemodynamic variables
Outcomes	Accidental awareness "Each patients was visited by a research nurse on the first day after the operation who asked if the patient was able to recall any intra‐operative events or remembered any dreams during the operation" "No patient reported recall of intraoperative events"
Identification	Country: Hong Kong Setting: University Hospital Authors name: WD Ngan Kee Institution: Prince of Wales Hospital, Shatin, Hong Kong Email: NR Address: NR
Aim of study	To compare the effect of FiO₂ of 0.3, 0.5 and 1.0 on umbilical cord blood oxygen content in participants having elective Caesarean section under anaesthesia
Notes	Obstetric patients. Anaesthetics in different groups aimed to give same overall MAC Sponsorship source: Direct Grant for research from the Chinese University of Hong Kong
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Patients were then randomly allocated to one of three groups by drawing of sequentially numbered sealed envelopes that each contained a computer‐generated randomization code"
Allocation concealment (selection bias)	Low risk	Quote: "randomly allocated to one of three groups by drawing of sequentially numbered sealed envelopes that each contained a computer‐generated randomization code." Comment: Probably was concealed allocation
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "Patients were not informed of the group allocation. One anaesthetist was responsible for controlling the delivery of the anaesthetic. Separate investigators were responsible for the blood sampling and analysis. To mask these investigators and the surgeon to the treatment, the anaesthesia machine was turned away so the monitors were not visible to them" Comment: Anaesthetists not blinded but anaesthetic inspired concentrations set
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "Each patient was visited on the first day after operation by a research nurse, who asked the patient if she was able to recall any intraoperative events" Comment: Not clear whether these research nurses were blinded. Participants were blinded
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: No reported attrition
Selective reporting (reporting bias)	Low risk	Comment: All relevant outcomes described in Methods were reported
Other bias	Low risk	Comment: None identified