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Br J Anaesth. 2006 Jun;96(6):754-60. Epub 2006 May 2.

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

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1
Department of Anesthesia and Perioperative Care, University of California, 521 Parnassus, San Francisco, 94143-0648, USA. leungj@anesthesia.ucsf.edu

Abstract

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 (N(2)O) 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 N(2)O resulted in an increased incidence of postoperative delirium than would be expected for patients not receiving N(2)O.

METHODS:

Patients who were >or=65 yr of age, undergoing non-cardiac surgery and requiring general anaesthesia were randomized to receive an inhalational agent and either N(2)O 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 N(2)O had no association with postoperative delirium.

CONCLUSIONS:

Exposure to N(2)O resulted in an equal incidence of postoperative delirium when compared with no exposure to N(2)O.

PMID:
16670110
DOI:
10.1093/bja/ael106
[Indexed for MEDLINE]
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