Monitoring consciousness: EEG-based measures of anesthetic depth

The current clinical practice of balanced anesthetic technique has obscured many of the observed physiologic parameters that once indicated the depth of anesthesia. Consequently, there is an increased need for assessing anesthetic effects on consciousness with processed electroencephalography (EEG). This article discusses the concept of anesthetic depth and the principles of EEG-based monitors, with a particular focus on bispectral analysis.