RELATIONSHIP BETWEEN CALCULATED BLOOD-CONCENTRATION OF PROPOFOL AND ELECTROPHYSIOLOGICAL VARIABLES DURING EMERGENCE FROM ANESTHESIA - COMPARISON OF BISPECTRAL INDEX, SPECTRAL EDGE FREQUENCY, MEDIAN FREQUENCY AND AUDITORY-EVOKED POTENTIAL INDEX

We studied four electrophysiological variables (bispectral index (BIS) , 95% spectral edge frequency (SEF), median frequency (MF) and auditor y evoked potential index (AEP index)) in 10 patients during emergence from anaesthesia. We compared correlation of the signals with graduall y decreasing calculated blood propofol concentrations, and evaluated t he signal differences between preinduction and emergence from anaesthe sia. Values of BIS, MF and SEF correlated with calculated blood concen trations of propofol during emergence from anaesthesia. The correlatio n was best with BIS, but was poor with MF and SEF at low calculated bl ood propofol concentrations. Although AEP index values did not correla te with calculated blood concentrations of propofol during emergence f rom anaesthesia, values after eye opening and before anaesthesia were well distinguished from those during emergence from anaesthesia. BIS c orrelated best with calculated blood concentrations of propofol. AEP i ndex appeared to distinguish the awake from asleep state.