Comparison of spontaneous frontal EMG, EEG power spectrum and bispectral index to monitor propofol drug effect and emergence

Background: The aim of this study was to investigate the accuracy of frontal spontaneous electromyography (SEMG) and EEG spectral edge frequency (SEF 95%), median frequency (MF), relative delta power (RDELTA) and bispectral index (BIS) in monitoring loss of and return of consciousness and hypnotic drug effect during propofol administration at different calculated plasma target concentrations. Methods: Propofol was administered by using a target-controlled infusion at different propofol steady-state concentrations. All variables were measured simultaneously at specific calculated concentrations and endpoints. Results: Loss of consciousness was accurately monitored by BIS, SEMG and SEF 95%, and propofol drug effect by BIS only Return of consciousness was predicted by BIS, MF and SEF 95%. Due to the biphasic EEG pattern of propofol and the lack of reproducible data at specific propofol concentrations, the clinical usefulness of SEF 95%, MF and RDELTA was very Limited. SEMG was useful to detect loss and return of consciousness, but without predictive value. Conclusions: The BIS might be an accurate measure to monitor depth of anaesthesia and hypnotic drug effect. Other neurophysiologic measures have limited value to monitor depth of anaesthesia and hypnotic drug effect. (C) Acta Anaesthesiologica Scandinavica 42 (1998).