Topographic electroencephalogram of propofol-induced conscious sedation.

Objectives: To determine the effects of increasing doses of propofol that induce conscious sedation on the topographic electroencephalogram (EEG) of human volunteers and to test the hypothesis that more frontal brain areas are affected by low doses of propofol.

Methods: The scalp EEG was recorded monopolarly from 16 different sites based on the 10-20 International System. Microcomputer-based hardware and RHYTHM 7.1 software were used to obtain quantitative power frequency topographic EEG data. A total of 10 normal adult volunteers were given incremental doses of propofol targeted to plasma concentrations of 0 to 1200 ng/ml.

Results: Sedative concentrations of propofol produced a dramatic increase in beta 1, an increase in alpha 2 and beta 2, and an increase in delta activity at the largest concentration, with almost no change in theta activity. The increase in beta 1 activity had a linear correlation with plasma propofol levels (r = 0.9). Topographic mapping indicated that beta 1 activation was primarily in the frontal and central regions, with focal changes more in the left hemisphere.

Conclusions: Topographic brain EEG mapping techniques indicate that frontal brain beta 1 EEG activity may be useful as an objective brain index of propofol conscious sedation.