Anesthetic Depth and Postoperative Delirium Trial - 2

Recently, it has been proposed that use of a processed electroencephalogram (EEG) monitor during surgery may be associated with a lower rate of postoperative delirium. In fact, some suggest that older patients undergoing surgery should routinely be monitored with an anesthetic depth monitor to allow the titration of anesthetics or sedation medications to lighter levels to promote better postoperative cognitive outcomes. Recent studies, including preliminary results from our group, have demonstrated electroencephalogram (EEG) suppression to be an independent risk factor for postoperative delirium. Prior studies that have focused on risk prediction have shown age and prior cognitive impairment to be the most consistent risk factors for postoperative delirium. However, as of yet, no clinical trial has identified a relationship whether use of processed EEG monitor resulted in a reduction of incident postoperative delirium through a reduction in EEG suppression, with proper consideration of patients' baseline cognitive status as a potential moderator. Additionally, use of anesthetic depth monitor to keep patients' anesthetic depth above a specified value has never been validated or proven to be feasible or safe. Accordingly, the investigators plan an exploratory study to: 1) determine whether the use of processed EEG to keep anesthetic depth above a specified level, results in a reduction in EEG suppression when compared to standard anesthetic care, 2) to determine whether preoperative level of cognitive function moderates the effect of group assignment on EEG suppression, and 3) to determine the feasibility and safety of using processed EEG-guided to keep patients' anesthetic depth above a specified value. A secondary aim was to determine the effect size for the intervention to reduce postoperative delirium for subjects with and without preoperative cognitive impairment for a future trial.