Nitrous oxide and serious long-term morbidity and mortality in the evaluation of nitrous oxide in the gas mixture for anaesthesia (ENIGMA)-II trial

K. Leslie, P.S. Myles, J. Kasza, A. Forbes, P.J. Peyton, M.T.V. Chan, Mike Paech, D.I. Sessler, W.S. Beattie, P.J. Devereaux, S. Wallace

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    Abstract

    © 2015, the American Society of Anesthesiologists, Inc. Wolters Kluwer Health, Inc. Background: The Evaluation of Nitrous Oxide in the Gas Mixture for Anaesthesia (ENIGMA)-II trial randomly assigned 7,112 noncardiac surgery patients at risk of perioperative cardiovascular events to 70% N2O or 70% N2 groups. The aim of this follow-up study was to determine the effect of nitrous oxide on a composite primary outcome of death and major cardiovascular events at 1 yr after surgery. Methods: One-year follow-up was conducted via a medical record review and telephone interview. Disability was defined as a Katz index of independence in activities of daily living score less than 8. Adjusted odds ratios and hazard ratios were calculated as appropriate for primary and secondary outcomes. Results: Among 5,844 patients evaluated at 1 yr, 435 (7.4%) had died, 206 (3.5%) had disability, 514 (8.8%) had a fatal or nonfatal myocardial infarction, and 111 (1.9%) had a fatal or nonfatal stroke during the 1-yr follow-up period. Exposure to nitrous oxide did not increase the risk of the primary outcome (odds ratio, 1.08; 95% CI, 0.94 to 1.25; P = 0.27), disability or death (odds ratio, 1.07; 95% CI, 0.90 to 1.27; P = 0.44), death (hazard ratio, 1.17; 95% CI, 0.97 to 1.43; P = 0.10), myocardial infarction (odds ratio, 0.97; 95% CI, 0.81 to 1.17; P = 0.78), or stroke (odds ratio, 1.08; 95% CI, 0.74 to 1.58; P = 0.70). Conclusion: These results support the long-term safety of nitrous oxide administration in noncardiac surgical patients with known or suspected cardiovascular disease.
    Original languageEnglish
    Pages (from-to)1267-1280
    JournalAnesthesiology
    Volume123
    Issue number6
    DOIs
    Publication statusPublished - Dec 2015

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