OBJECTIVE: To evaluate whether elevated intraoperative blood glucose concentrations are associated with an increased risk of long-term neurologic dysfunction in patients at risk for ischemic brain injury. PATIENTS AND METHODS: Data from 1000 patients were retrieved from the Intraoperative Hypothermia for Aneurysm Surgery Trial database. All patients were recruited between February 2000 and April 2003, and underwent surgery for aneurysm clipping within 14 days of subarachnoid hemorrhage. Gross neurologic and neuropsychological function was evaluated at 3 months after surgery using certified observers and standardized assessment instruments. Intraoperative blood glucose concentrations, measured once when the aneurysm clip was placed, were correlated with neurologic outcome using both univariable and multivariable logistic regression analyses. RESULTS: Blood glucose concentrations at the time of aneurysm clipping ranged from 59 to 331 mg/dL. At 3 months after surgery, those with blood glucose concentrations of 129 mg/dL or more (upper 2 quartiles) were more likely to have impaired cognition (P=.03). Those with glucose concentrations of 152 mg/dL or more (upper quartile) were more likely to experience deficits in gross neurologic function assessed by the National Institutes of Health Stroke Scale (P<.05), but not other scoring scales. Length of stay in intensive care units was longer in those with glucose concentrations of 129 mg/dL or more, but there was no difference among glucose groups in the duration of overall hospital stay or the fraction of patients discharged to home. CONCLUSION: In patients at high risk for ischemic brain injury, intraoperative hyperglycemia, of a magnitude commonly encountered clinically, was associated with long-term changes in cognition and gross neurologic function.