Automatic EEG Monitoring During Anesthesia

Abstract

EEG monitoring means that the spontaneous electroencephalogram is used as a parameter to evaluate brain function during critical conditions of the patient in order to prevent irreversible damage of the brain. The method has been used already for a long period (Gibbs et al., 1937; Bickford, 1950; Meyer and Gastaut, 1961; Shapiro, 1978; Prior, 1979; Pronk and Simons, 1982; Simons and Pronk, 1982). There are a number of circumstances in which this type of monitoring may be very succesful. A good review may be found in Prior (1979). Concerning anesthesia one may distinguish between EEG monitoring of the anesthesia itself (Bimar et al., 1977; Eger, 1978) in which one tries to determine the depth of anesthesia and especially the moment at which the patient looses consciousness and EEG monitoring during anesthesia under conditions which may lead to serious risks to the brain. To determine the depth of anesthesia a number of sophisticated methods based on the spontaneous on-going EEG have been developed (McEwen et al., 1975; McEwen, 1976; Berezowski et al., 1976). In a routine setting these methods have not been succesful up to now (Saunders, 1981) (Fig. 1). A combination with other EEG techniques such as evoked responses may be promising in future (Grundy et al., 1982). By means of the EEG one may easily follow global alterations of brain function during anesthesia (Faulconer et al., 1960; Sadove et al., 1967; Uhl, 1977; Prior, 1979). This may be of help to stabilize the anesthesia. It still needs intermediate action of the anesthesiologist. Servo-anesthesia with the help of the EEG has been investigated (Bickford, 1950; Verzeano, 1951; Belville et al., 1954), but routine methods have not been realised up to now.