EEG frequency progression during induction of anesthesia: from start of infusion to onset of burst suppression pattern.
ABSTRACT The anesthetic infusion with propofol influences EEG activity rather smoothly by changing the amplitude activity in different frequency bands. This results in a frequency progression pattern (FPP) which can be related to the depth of anesthesia. An iterative algorithm is proposed for the estimation of the shape of this pattern. The presented method is applied to the data recorded from the start of the propofol anesthetic infusion to the onset of the burst suppression pattern (BSP) with nine patients. The results reveal the underlying FPP and how the onset of the BSP is related to it. The proposed method offers potential for the development of automatic assessment systems for the depth of anesthesia.
- Anesthesia & Analgesia 02/1993; 76(1):1-6. · 3.30 Impact Factor
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ABSTRACT: Our purpose is to find out whether the Loss of obeying a Verbal Command (LVC) and the preceding progression of the EEG frequency patterns are mutually related during an anesthetic induction. EEG was analyzed from sixteen patients, anesthetized with a fixed rate infusion of propofol (30 mg/kg/h). An artifact-purified EEG from electrode Fz referenced to the average of mastoid signals was filtered to consecutive 4 Hz frequency passbands with a filter bank. Signal envelope time-series were computed for all the passbands and studied as a function of the elapsed induction time t and as a function of the relative time r, which is t divided by the time of the LVC. A frequency band specific biphasic activity pattern progressed from high towards low frequencies systematically and uniformly in the population studied when presented on the relative time scale r, irrespective of individual responses to the dosage. The grouping of the individual progression patterns on the r scale indicates a strong relation between the EEG spectral behavior and the LVC. EEG may provide phenomenological grounds for a continuous control variable of a sedative drug effect, even in between the discrete clinical end-points.Clinical Neurophysiology 10/2005; 116(9):2069-76. · 3.14 Impact Factor
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ABSTRACT: The time course of four EEG effect variables, amplitude in the 2-5 Hz and in the 11-15 Hz band, spectral edge frequency 95% (SEF95), and bispectral index (BIS), in response to increasing concentrations of thiopental, propofol, etomidate, midazolam, or sevoflurane during a 10 min induction of anaesthesia was studied in 25 patients to determine the existence of a biphasic effect and to study the relationship of the EEG effect to the moment of loss of consciousness. A biphasic effect, that is, an initial increase of the effect variable followed by a decrease at higher concentrations, during the transition from consciousness to unconsciousness was found in EEG amplitude (both frequency bands) and in SEF95 for all anaesthetics except midazolam. There was a concentration-related decrease in BIS for all anaesthetics. There was no consistent relationship between the time of occurrence of the peak EEG effect, or the value of the EEG variable and the moment of loss of consciousness. With rapidly changing drug concentrations during the induction of anaesthesia, none of these EEG effect variables could be correlated to the moment of loss of consciousness.BJA British Journal of Anaesthesia 04/2001; 86(3):354-60. · 4.24 Impact Factor