[Automatic analysis of electroencephalogram: what is its value in the year 2000 for monitoring anesthesia depth?]

Spontaneous EEG has been proposed for monitoring depth of anaesthesia and adjusting anesthetic drugs doses. This review describes the main features of spontaneous EEG, the principles of EEG signal analysis used in anaesthesia, and the EEG effects of the different anesthetic drugs in adults and children. Then, the correlations between EEG parameters changes and clinical signs of anesthesia (loss of consciousness and memory, lack of movement and haemodynamic stability despite noxious stimulations) are analyzed. The best signal analysis technique available today for routine use seems to be bispectral analysis, which returns, in the available monitors, a single number called bispectral index or BIS. Based upon the recent literature, clinical uses, performances and limits of use of BIS are described and discussed.