Effect of nitrous oxide on neurologic and neuropsychological function after intracranial aneurysm surgery.
BACKGROUND
Laboratory studies suggest that nitrous oxide augments brain injury after ischemia or hypoxia. The authors examined the relation between nitrous oxide use and outcomes using data from the Intraoperative Hypothermia for Aneurysm Surgery Trial.


METHODS
The Intraoperative Hypothermia for Aneurysm Surgery Trial was a prospective randomized study of the impact of intraoperative hypothermia (temperature = 33 degrees C) versus normothermia (temperature = 36.5 degrees C) in patients with aneurysmal subarachnoid hemorrhage undergoing surgical clipping. Anesthesia was dictated by a limited-options protocol with the use of nitrous oxide determined by individual anesthesiologists. All patients were assessed daily for 14 days after surgery or until hospital discharge. Neurologic and neuropsychological testing were conducted at 3 months after surgery. Outcome data were analyzed via both univariate tests and multivariate logistic regression analysis correcting for factors thought to influence outcome. An odds ratio (OR) greater than 1.0 denotes a worse outcome in patients receiving nitrous oxide.


RESULTS
Outcome data were available for 1,000 patients, of which 373 received nitrous oxide. There was no difference between groups in the development of delayed ischemic neurologic deficit. At 3 months after surgery, there were no significant differences between groups in any outcome variable: Glasgow Outcome Score (OR, 0.84; 95% confidence interval [CI], 0.63-1.14; P = 0.268), National Institutes of Health Stroke Scale (OR, 1.29; 95% CI, 0.96-1.73; P = 0.087), Rankin Disability Score (OR, 0.84; 95% CI, 0.61-1.15; P = 0.284), Barthel Activities of Daily Living Index (OR, 1.01; 95% CI, 0.68-1.51; P = 0.961), or neuropsychological testing (OR, 1.26; 95% CI, 0.85-1.87; P = 0.252).


CONCLUSIONS
In a population of patients at risk for ischemic brain injury, nitrous oxide use had no overall beneficial or detrimental impact on neurologic or neuropsychological outcomes.
McGregor
Diana G
DG
Department of Anesthesiology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
Lanier
William L
WL
Pasternak
Jeffrey J
JJ
Rusy
Deborah A
DA
Hogan
Kirk
K
Samra
Satwant
S
Hindman
Bradley
B
Todd
Michael M
MM
Schroeder
Darrell R
DR
Bayman
Emine Ozgur
EO
Clarke
William
W
Torner
James
J
Weeks
Julie
J
D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007036:Hypothermia, Induced / Q000379:methods; D002532:Intracranial Aneurysm / Q000473:pathology / Q000523:psychology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D015337:Multicenter Studies as Topic / Q000379:methods; D009422:Nervous System Diseases / Q000139:chemically induced* / Q000473:pathology / Q000523:psychology*; D009483:Neuropsychological Tests; D009609:Nitrous Oxide / Q000009:adverse effects*; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic / Q000379:methods; D013345:Subarachnoid Hemorrhage / Q000473:pathology / Q000523:psychology / Q000601:surgery
D009609:Nitrous Oxide