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BJA Advance Access originally published online on May 2, 2006
British Journal of Anaesthesia 2006 96(6):754-760; doi:10.1093/bja/ael106
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© The Board of Management and Trustees of the British Journal of Anaesthesia 2006. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

Nitrous oxide does not change the incidence of postoperative delirium or cognitive decline in elderly surgical patients

J. M. Leung1,*, L. P. Sands2, L. E. Vaurio1 and Y. Wang3,4

1 Department of Anesthesia and Perioperative Care, University of California 521 Parnassus, San Francisco, CA 94143-0648, USA
2 School of Nursing, Center on Aging and the Life Course, Purdue University West Lafayette, IN 47907-2069, USA
3 Department of Statistics, Purdue University West Lafayette, IN 47907-2067, USA

*Corresponding author. E-mail: leungj{at}anesthesia.ucsf.edu

Background. Postoperative delirium and cognitive decline are common in elderly surgical patients after non-cardiac surgery. Despite this prevalence and clinical importance, no specific aetiological factor has been identified for postoperative delirium and cognitive decline. In experimental setting in a rat model, nitrous oxide (N2O) produces neurotoxic effect at high concentrations and in an age-dependent manner. Whether this neurotoxic response may be observed clinically has not been previously determined. We hypothesized that in the elderly patients undergoing non-cardiac surgery, exposure to N2O resulted in an increased incidence of postoperative delirium than would be expected for patients not receiving N2O.

Methods. Patients who were ≥65 yr of age, undergoing non-cardiac surgery and requiring general anaesthesia were randomized to receive an inhalational agent and either N2O with oxygen or oxygen alone. A structured interview was conducted before operation and for the first two postoperative days to determine the presence of delirium using the Confusion Assessment Method.

Results. A total of 228 patients were studied with a mean (range) age of 73.9 (65–95) yr. After operation, 43.8% of patients developed delirium. By multivariate logistic regression, age [odds ratio (OR) 1.07; 95% confidence interval (CI) 1.02–1.26], dependence on performing one or more independent activities of daily living (OR 1.54; 95% CI 1.01–2.35), use of patient-controlled analgesia for postoperative pain control (OR 3.75; 95% CI 1.27–11.01) and postoperative use of benzodiazepine (OR 2.29; 95% CI 1.21–4.36) were independently associated with an increased risk for postoperative delirium. In contrast, the use of N2O had no association with postoperative delirium.

Conclusions. Exposure to N2O resulted in an equal incidence of postoperative delirium when compared with no exposure to N2O.

4Present address: Staff Statistician, University of Pittsburgh, PA 15213, USA


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Delirium after elective surgery among elderly patients taking statins
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[Abstract] [Full Text] [PDF]

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Nitrous oxide and cognitive function in the elderly
Mohammad R. Abdul Rahim
British Journal of Anaesthesia, 7 Dec 2006 [Full text]
Re: Nitrous oxide and cognitive function in the elderly
Jacqueline M. Leung, M.D., M.P.H., et al.
British Journal of Anaesthesia, 15 Dec 2006 [Full text]

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