EFFECTS OF PROPOFOL ON NOCICEPTIVE RESPONSE AND POWER SPECTRA OF ELECTROENCEPHALOGRAPHIC AND SYSTEMIC ARTERIAL-PRESSURE SIGNALS IN THE RAT - CORRELATION WITH PLASMA-CONCENTRATION

We applied simultaneous spectral analysis of electroencephalographic ( EEG) and systemic arterial pressure signals in Sprague-Dawley rats to monitor the status of consciousness and cardiovascular functions durin g intravenous anesthesia with propofol and to assess their correlation s with plasma propofol concentration. Our results support the hypothes is that a 'threshold' plasma concentration (1.7-1.8 mu g/ml) exists fo r propofol anesthesia. This threshold level, we further showed, may be attained by both i.v. bolus injection and continuous infusion, althou gh the pharmacokinetic profiles, as well as EEG and hemodynamic correl ates, may be different. Continuous, on-line power spectral analysis of EEG signals revealed that the degree of reduction in the power densit y of the theta and delta bands and root mean square value paralleled t he level of anesthesia. Significant suppression of both alpha and beta components occurred only concomitant with EEG burst suppression. At t he subanesthetic dose, i.v. infusion of propofol increased preferentia lly the power density of the theta and delta bands, suggesting the val idity of including sedation as a nonhypnotic therapeutic application o f propofol. We also found that appreciable cardiovascular suppression took place only upon anesthetic doses of propofol. Power spectral anal ysis of systemic arterial pressure signals indicated that this was acc ompanied by a progressive depression of spectral parameters that signi fy peripheral vascular resistance and baroreceptor reflex response.