Myles 2008a.
| Methods | Muli‐centre RCT | |
| Participants |
Setting: 2 hospitals from Australia and Hong Kong Inclusion criteria: patients undergoing elective noncardiac surgery, with risk factors or a known history of coronary artery disease (hypertension, diabetes, age older than 60 years, or preexisting history of coronary artery disease) Exclusion criteria: patients expected to require a high inspired oxygen concentration intraoperatively or with any relative contraindication to nitrous oxide (volvulus, pulmonary hypertension, increased intracranial pressure) Participant numbers: 59 randomly assigned; 59 analysed |
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| Interventions | Intervention: patients had maintenance of general anaesthesia with nitrous oxide and FiO2 0.3, and one of three other hypnotic agents (isoflurane, sevoflurane, or propofol) at the discretion of the anaesthesiologist. Control: patients had their anaesthesia maintained with FiO2 0.8 or FiO2 0.3, but without nitrous oxide. | |
| Outcomes |
Secondary outcomes: Length of hospital stay |
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| Notes | — | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | Quote: "Patients were randomly allocated via a computer‐generated random list." |
| Allocation concealment (selection bias) | Low risk | Quote: "The random sequence was concealed in opaque, sealed envelopes." |
| Blinding of participants and personnel (performance bias) All outcomes | Low risk | Quote: "Administration and group identity were concealed from the surgeon and research staff." |
| 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 | Unclear risk | — |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | No missing data. |
| Selective reporting (reporting bias) | High risk | Not all of the study's pre‐specified primary outcomes (e.g. myocardial infarction) had been reported. |
| Other bias | Low risk | No other potential sources of bias were detected. |