The P300 event-related potential during propofol sedation: a possible marker for amnesia?

We have studied the effects of conscious sedation with propofol on long latency components of the auditory event-related potential (ERP) in 10 normal volunteers (aged 21-41 yr) receiving propofol 75 micrograms kg-1 min-1 i.v. We examined the effects of propofol on ERP amplitudes and latencies, and their relationship to delayed recognition performance using a verbal memory test, a selective attention task (button pushing) and serum concentrations of propofol. During infusion of propofol, subjects were mildly sedated, oriented and readily responsive to verbal commands. ERP were recorded from monopolar FZ, CZ and PZ electrodes. We used a standard paradigm requiring selective attention to randomly occurring stimuli associated with a task (button push). The peak-to-peak amplitudes and latencies of the N2 and P3 waves were obtained before and during infusion, and 15, 100 and 170 min after infusion. Propofol produced a 70% decrease in the amplitude of P3 (P < 0.0001) from baseline and a 50% increase in reaction time. The differential response to target compared with non-target stimuli was maintained during infusion for both N2 and P3. Memory performance correlated more strongly with changes in P3 amplitude (r = 0.59) than with serum propofol concentrations (r = -0.07), although this correlation with memory did not reach statistical significance (P = 0.08). We conclude that P3 amplitude was profoundly affected by propofol given in sedative concentrations.