Effect of nitrous oxide use on long-term neurologic and neuropsychological outcome in patients who received temporary proximal artery occlusion during cerebral aneurysm clipping surgery.
BACKGROUND
The authors explored the relationship between nitrous oxide use and neurologic and neuropsychological outcome in a population of patients likely to experience intraoperative cerebral ischemia: those who had temporary cerebral arterial occlusion during aneurysm clipping surgery.


METHODS
A post hoc analysis of a subset of the data from the Intraoperative Hypothermia for Aneurysm Surgery Trial was conducted. Only subjects who had temporary arterial occlusion during surgery were included in the analysis. Metrics of short-term and long-term (i.e., 3 months after surgery) outcome were evaluated via both univariate and multivariate logistic regression analysis. An odds ratio (OR) greater than 1.0 denotes a worse outcome in patients receiving nitrous oxide.


RESULTS
The authors evaluated 441 patients, of which 199 received nitrous oxide. Patients receiving nitrous oxide had a greater risk of delayed ischemic neurologic deficits (i.e., the clinical manifestation of vasospasm) (OR, 1.78, 95% confidence interval [CI], 1.08-2.95; P = 0.025). However, at 3 months after surgery, there was no difference in any metric of gross neurologic outcome: Glasgow Outcome Score (OR, 0.67; CI, 0.44-1.03; P = 0.065), Rankin Score (OR, 0.74; CI, 0.47-1.16; P = 0.192), National Institutes of Health Stroke Scale (OR, 1.02; CI, 0.66-1.56; P = 0.937), or Barthel Index (OR, 0.69; CI, 0.38-1.25; P = 0.22). The risk of impairment on at least one test of neuropsychological function was reduced in those who received nitrous oxide (OR, 0.56; CI, 0.36-0.89; P = 0.013).


CONCLUSIONS
In this patient population, use of nitrous oxide was associated with an increased risk for the development of delayed ischemic neurologic deficits; however, there was no evidence of detriment to long-term gross neurologic or neuropsychological outcome.
Pasternak
Jeffrey J
JJ
Department of Anesthesiology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA. pasternak.jeffrey@mayo.edu
McGregor
Diana G
DG
Lanier
William L
WL
Schroeder
Darrell R
DR
Rusy
Deborah A
DA
Hindman
Bradley
B
Clarke
William
W
Torner
James
J
Todd
Michael M
MM
D000328:Adult; D021721:Balloon Occlusion / Q000009:adverse effects; D002536:Cerebral Arteries / Q000187:drug effects / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002532:Intracranial Aneurysm / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009422:Nervous System Diseases / Q000139:chemically induced / Q000503:physiopathology / Q000523:psychology*; D009483:Neuropsychological Tests; D019635:Neurosurgical Procedures / Q000009:adverse effects / Q000295:instrumentation*; D009609:Nitrous Oxide / Q000008:administration & dosage* / Q000009:adverse effects; D011183:Postoperative Complications / Q000139:chemically induced / Q000503:physiopathology / Q000523:psychology*; D011446:Prospective Studies; D013525:Surgical Instruments / Q000009:adverse effects; D016896:Treatment Outcome
D009609:Nitrous Oxide