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Nitrous oxide exposure does not seem to be associated with increased mortality, stroke, and myocardial infarction: a non-randomized subgroup analysis of the General Anaesthesia compared with Local Anaesthesia for carotid surgery (GALA) trial
British Journal of Anesthesia, 06/21/2012
Sanders RD et al. – Given the greater prevalence of vascular risk factors in the nitrous oxide group and the lack of any definite effect on the primary outcome measure, these data do not support a clinically meaningful adverse effect of nitrous oxide on the composite outcome in patients undergoing carotid surgery.
Methods- One thousand seven hundred and seventy–three patients underwent GA, but 158 patients were excluded from this analysis as nitrous oxide use was unknown.
- The decision to use nitrous oxide was at the discretion of the anaesthetist and was not randomized.
- Six hundred and seventy–one patients received nitrous oxide and 944 patients did not.
- Logistic regression was used to analyse the same primary outcome as the original trial (risk of death, stroke, or myocardial infarction within 30days of the operation).
- Patients who received nitrous oxide were more likely to have had coronary artery disease, peripheral vascular disease, and atrial fibrillation (all P<0.05).
- Overall, there were 35 (5.2%) primary outcome events in patients receiving nitrous oxide compared with 44 (4.7%) in those who did not [relative risk 1.12, 95% confidence interval (CI: 0.73, 1.73); P=0.63].
- The adjustment for the imbalanced baseline variables using logistic regression reduced the point estimate of harm for nitrous oxide [adjusted odds ratio 1.09, 95% CI (0.68, 1.74); P=0.73].
