Auditory steady-state response, upper facial EMG, EEG and heart rate as predictors of movement during isoflurane-nitrous oxide anaesthesia

Abstract

We have studied the relationship between patient movement and changes in the auditory steady-state evoked potential, upper facial muscle electromyogram (FEMG), electroencephalographic-zero crossing frequency (EEG-ZCF) and heart rate during emergence from anaesthesia. Twelve healthy patients underwent surgery during stable isoflurane-nitrous oxide-oxygen anaesthesia without neuromuscular block. After skin closure, anaesthesia was discontinued abruptly while mechanical ventilation was continued until the patient moved. The magnitude of change in each physiological signal was evaluated in decibels (dB). Both the auditory steady state evoked potential and FEMG showed significant increases in amplitude during the last 5-min period before movement (6.1 and 10.7 dB, respectively). EEG-ZCF increased rapidly after anaesthesia was discontinued (2.5 dB) but there was no further increase in activity before movement. Heart rate did not change before movement. The use of the decibel transformation offers a promising method of displaying and interpreting changes in physiological variables during anaesthesia.

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

“…A monotonic increasing trend during emergence was found in SEF 95% and BIS. Yli-Hankala et al (5) defined a reliable measure to predict the return of consciousness as one showing a statistically significant change from pre-recovery baseline during anaesthesia at least 1 min before return of consciousness. In our study, at 1 min before reaching an OAA/S >2, BIS, SEF 95% and MF were statistically different from baseline.…”

“…Spontaneous frontal electromyography (SEMG) has been shown to be a useful indicator of pending arousal (5). Sudden increases in the amplitude of SEMG activity in frontal muscles during surgery indicate enhanced patient responsiveness (6).…”

“…Due to great interindividual variability in the amplitude of the SEMG, this technique has not gained wide clinical acceptance. Nevertheless, some successful applications of the SEMG on the detection of arousal during anaesthesia have been published (5,7) and a new revival of the application of this technique can be found in recent literature (8). To date, insufficient research has been performed and further studies will be required to determine the utility of SEMG as a monitor of adequate anaesthesia and hypnotic drug effect.…”

“…An additional problem when studying the changes in different computerized neurophysiological variables is caused by the difference in units of measurement. Therefore, a decibel (dB) transformation of the various measures is useful to facilitate the plotting of the results by providing a uniform scale and eliminating the confounding effects of different frequency distributions (5,7). To the best of our knowledge, a comparative study of the accuracy of the chosen neurophysiological measures in monitoring different anaesthetic states, hypnotic drug effect and accuracy of these different variables to monitor loss of consciousness and emergence, using a dB transformation, has not been reported previously.…”

A new device to reduce the consumption of a halogenated anaesthetic agent*

“…Isoflurane was initially titrated to an end-tidal concentration of 0.5% [3]. It was later adjusted according to electroencephalography (EEG), electromyography (EMG) and clinical response [4]. A Datex Anaesthesia Brain Monitor and Datex AS 3 (Datex Instrumentarium, Helsinki, Finland) were used for EEG, EMG, and measurement of gases, vapour and haemodynamics.…”