Prediction of neurological outcome using bispectral index monitoring in patients with severe ischemic-hypoxic brain injury undergoing emergency surgery

Abstract

Background: Predicting outcome from ischemic-hypoxic brain injury can be difficult in patients rushed to the operating room for time-critical emergency surgery. The authors chose to evaluate the prognostic ability of bispectral index (BIS) in this setting.

Methods: Twenty-five critically ill, unconscious patients with ischemic-hypoxic brain injury undergoing emergency surgery were prospectively studied. Clinical evaluation, laboratory investigations, BIS, and burst suppression ratio were recorded before and during surgery. Neurologic outcome of the patients was measured according to the Glasgow outcome scale at 30 days after injury, with poor neurologic outcome defined as severe disability or death.

Results: The incidence of poor neurologic outcome was 68%. Neither clinical judgment (P = 0.40) nor pupillary responses (P = 0.21) were predictive of neurologic outcome after surgery. An abnormal BIS trace was strongly associated with poor neurologic outcome, positive likelihood ratio 6.6 (95% CI 1.7-36.4; exact test P = 0.002). Some BIS values were significantly different when comparing patients with and without poor outcome: c-statistics for the average BIS and maximal electroencephalographic burst-suppression were 0.80 (95% CI 0.62-0.98; P = 0.017) and 0.84 (95% CI 0.68-0.99; P = 0.007), respectively. A normal BIS (P < 0.0005) but not clinical judgment (P = 0.16) could identify a group of patients more likely to survive with a good neurologic outcome.

Conclusions: BIS, when compared with clinical judgment and routine laboratory tests, provides useful information that may identify patients with a good chance of recovery after ischemic-hypoxic brain injury requiring emergency surgery.