Electrophysiologic effects of propofol sedation

The scalp electroencephalogram (EEG), the long latency cognitive P300 auditory evoked response (AER), and reaction times were recorded in 10 volunteers sedated with a computer-controlled infusion of propofol to target plasma concentrations of 0.3, 0.6, 0.9, and 1.2 μg/mL. The observed mean ± SE venous plasma concentrations were 0.152 ± 0.042, 0.372 ± 0.078, 0.679 ± 0.104, and 1.065 ± 0.112 μg/mL, respectively. Scalp EEG topographic mapping revealed that β₁ activation was primarily frontal and central with relative sparing of the temporal lobes. The P300 response was dramatically reduced by propofol in a concentration-dependent manner, even though the subjects were conscious but clearly sedated. Mean ± SE reaction times were increased by propofol sedation from 347 ± 35 ms (control) to 391 ± 48, 460 ± 70, 549 ± 64, and 622 ± 120 ms at increasing mean venous plasma propofol concentrations. The mean percentage ± SE of correct responses decreased from 98.1 ± 2.0 (control) to 99.1 ± 1.7, 87.4 ± 9.2, 82.8 ± 12.9, and 69.8 ± 20.9 at increasing propofol concentrations. Dramatic alterations in the EEG, P300 response, and reaction times were observed, especially with the higher plasma concentrations which produced conscious sedation.