Median EEG frequency is more sensitive to increases in sympathetic activity than bispectral index

Sympathetic heart rate variability is correlated with the increase in plasma catecholamines during rapid opioid detoxification. We evaluated whether the bispectral index, median frequency, or 95% spectral edge of the electroencephalogram are sensitive to the sympathetic response seen during reversal of opioid dependence. Eight patients undergoing rapid opioid detoxification gave informed consent. Two-channel frontal electroencephalogram was measured. Sympathetic heart rate variability was measured in 256 second segments by Fourier transform of continuous heart rate and the low frequency segment (0.02-0.13 Hz) analyzed for sympathetic function. Patients were anesthetized with propofol infusion. After a 30-60 min steady state, naloxone was infused intravenously at a rate of 25 mg/30 min, followed by an infusion of 1 mg/hr. During induction of anesthesia, sympathetic heart rate variability decreased from 1.80 to 0.3, bispectral index from 86 to 47, median frequency from 10.2 to 3.4, spectral edge from 23.5 to 16.7 (all P<.05). During naloxone infusion, the median percent increase in sympathetic heart rate variability was 487% (P<.05), median frequency increased 163% (P<.05), bispectral index (10%), and spectral edge (7%) did not significantly change. The increase in median frequency was delayed compared to sympathetic heart rate variability and median frequency remained elevated after sympathetic heart rate variability returned to anesthetized baseline in 5 of 8 cases. Our results show that median frequency and sympathetic heart rate variability increase during opioid detoxification, but the time course of each response is different. Median frequency is a more sensitive electroencephalogram indicator of opioid reversal than bispectral index or spectral edge.