[Investigations on several EEG-parameters as indicators of the state of anaesthesia the median - a quantitative measure of the depth of anaesthesia (author's transl)].

32 cases with Etomidate-, Ethrane- and Fentanyl-application have been investigated in order to evaluate a common EEG-index indicating the depth of anaesthesia. The following parameters are regarded: the mean amplitude, the relative parts of the powerspectrum for the frequency bands 0.5--2 Hz, 2--5 Hz, 5--8 Hz, 8--13 Hz, 13--24 Hz, alpha-delta-index, the beta-delta-index, the median of the powerspectrum. The median of the powerspectrum gains the best correlation to anaesthetic depth for adequate anaesthesia, which is determined by the common clinical vegetative signs. Anaesthesia which is unnecessarily deep is better indicated by a biparametric representation of both median and mean amplitude.