Awareness in cardiac anesthesia

Cardiac surgery represents a sub-group of patients at significantly increased risk of intraoperative awareness. Relatively few recent publications have targeted the topic of awareness in this group. The aim of this review is to identify areas of awareness research that may equally be extrapolated to cardiac anesthesia in the attempt to increase understanding of the nature and significance of this scenario and how to reduce it.

The formation of both implicit and explicit memory during anesthesia may be the result of fluctuations in hypnotic state. Owing to the low incidence of awareness, prospective studies produce inadequate patient numbers to clearly identify risks, causes and sequelae of intraoperative awareness. A recent analysis of case reports has identified two main risk factors for intraoperative awareness. Awareness research increasingly focuses on refining processed electroencephalography (EEG) monitors and establishing their effectiveness in reducing awareness, but with conflicting results.

Identification of high-risk patients, the use of balanced anesthesia techniques and increased vigilance on the part of the anesthetist will go a long way in preventing intraoperative awareness. There is evidence that using processed EEG monitors reduces the incidence of awareness. However, understanding their limitations and interpatient variability in dose-response curves, and interpreting the data in relation to the specific drugs and techniques used is paramount.