[Electrophysiological evaluation of diazepam anesthetic effect by "automated fluctuation analysis" of high frequency EEG in human].

"Automated fluctuation analysis" of human scalp EEG was made in order to evaluate anaesthetic effect of intravenous diazepam injection. Seven patients without disturbed consciousness were utilized for this study. Analytical system is composed of high fidelity pre-amplifier and signal processor. After 10,000 amplification of the signal, A/D conversion and Fast Fourier Transform were programmed with following parameters, sweep time; 12 sec., frequency resolvability; 1.2 Hz, frequency limit; 1 kHz, Fourier points; 2048 and Fourier time; 15. Power spectral density (PSD) was displayed on log-log graph. The best curve fitting program was next applied to the following equation, S(f) = S1/[1 + (f/fcl)2]+S2/[1 + (f/fc2)2] S(f): power spectral density, S1,S2: plateau levels of the initial and the second Lorentz, fcl, fc2: the corner or half power frequencies of the initial and the second Lorentz). As results, 1) PSDs of high frequency EEG up to 1 kHz were composed of double Lorentzian fluctuations. 2) From our previous animal study, it is suggested that the initial and the second Lorentz reflect the cortical and subcortical functions, respectively. 3) After diazepam injection, the second Lorentz was suppressed according to the time and dose and disappeared when the subjects fell asleep, and reappeared when waked up. There was excellent correlation between the consciousness level and the second Lorentz. 4) The initial Lorentz reflected higher cortical function; the ability of calculation or language were reduced after diazepam injection, and the hyperfrontal activity of the initial Lorentz disappeared. These results may suggest that "Automated Fluctuation Analysis" of high frequency EEG may have a potential to develop a new field in clinical neuroelectrophysiology.