DIE BEDEUTUNG EVOZIERTER POTENTIALE ZUR OBJEKTIVIERUNG VON BEWUSSTSEINSAUSSCHALTUNG UND ANALGESIE

Despite decades of experience in intraoperative monitoring of the effects of anaesthetic agents by electrophysiological methods, it has to date not been possible to define a generally applicable parameter for recording the depth of anaesthesia. The spontaneous electroencephalogram (EEG) records primarily the cortical functions. In contrast the evoked potentials also allow assessments of the function of the peripheral nervous system and subcortical parts of the central nervous system. The various types of EEG changes induced by different drugs make it more difficult to arrive at an unequivocal interpretation regarding the state of anaesthesia. In contrast the evoked potentials (EP) are not as a rule subject to drug-specific influences. Typical changes in the auditory (AEP) and the somatosensory (SEP) as well as the visual evoked potentials (VEP) are shown in dose-dependent reductions in amplitudes and latency prolongations. That is why various EP components have been proposed for monitoring of depth of anaesthesia. More recent findings indicate, however, that individual levels of anaesthesia may not be assessed by all modalities to the same degree. Since experimental studies have shown a close correlation between subjective pain sensation and late, cortically generated SEP, initial clinical trials are suggesting that these SEP components following specific stimulation indicate nociceptive transmission. Dose-dependent functional changes of the central nervous system can be recorded by both the EEG and the EP. It seems that intraoperative states of arousal in particular can be recorded by means of AEP.