[Is it possible to measure the depth of anesthesia using electroencephalogram?]

Although anesthetic monitoring has rapidly developed over the past few years, accidental awareness during general anesthesia still remains a significant clinical problem. It occurs in one out of thousand surgical patients. In addition to conventional clinical signs, the adequacy of anesthesia can be assessed for instance by monitoring the changes occurring in the electroencephalogram (EEG). The EEG effects of different anesthetics are, however, highly varied, and attempts to develop an unequivocal neurophysiological measure or quantity for human consciousness or unconsciousness have so far been unsuccessful.