A COMPARISON OF SPECTRAL EDGE, DELTA-POWER, AND BISPECTRAL INDEX AS EEG MEASURES OF ALFENTANIL, PROPOFOL, AND MIDAZOLAM DRUG EFFECT

Background: The effects of anesthetic drugs on electroencephalograms ( EEG) have been studied to develop the EEG as a measure of anesthetic d epth, Bispectral analysis is a new quantitative technique that measure s the consistency of the phase and power relationships and returns a s ingle measure, the bispectral index, The purpose of this study was to compare the performance of the bispectral index, version 1.1, with oth er spectral analysis EEG measures of drug effect for three commonly us ed anesthetic drugs. Methods: The EEG waveforms from 31 adults receivi ng infusions of alfentanil, propofol, or midazolam were analyzed, The time course of spectral edge (SE(95)), relative power in delta band, a nd bispectral index were related to the estimated effect-site concentr ation with use of a sigmoidal E(max) model to estimate the potency (IC 50) and the plasma effect-site equilibration rate constant (k(e0)) for each measure, The performance of the fitting was assessed by the coef ficient of correlation between predicted and observed effect, Results: Alfentanil induced a high-amplitude low-frequency EEG response, Propo fol induced a biphasic response. At low concentrations, both frequency and amplitude increased. When the concentration increased, the EEG sl owed and the amplitude decreased, High concentration produced burst su ppression, Midazolam increased EEG frequency and amplitude, Bispectral index, SE(95), and delta power yield similar estimates of IC50 and k( e0). Except for alfentanil, the performance of the modeling with the b ispectral index was as good that with SE,, or delta power. Conclusion: Bispectral analysis can be used as a measure of the EEG effects of an esthetic drugs.