[Evaluation of emergence from total intravenous anesthesia with propofol for long neurosurgery]

In six neurosurgical patients we examined their emergence from more than six hours of total intravenous anesthesia with propofol and fentanyl. The anesthesia was maintained properly with total intravenous anesthesia with propofol and fentanyl without nitrous oxide. We calculated the estimated blood concentration of propofol from the anesthesia record using a three-compartment pharmacokinetic model. The patients were extubated after they had shown good awareness. The average time for extubation was 18 minutes after discontinuation of propofol infusion. The mean estimated concentration of propofol at the extubation was 1.36 micrograms.ml-1 (range: 1.1-1.5 micrograms.ml-1). The estimated emergence times in these cases, also calculated with the pharmacokinetic model, correlated significantly with the time from discontinuation of propofol infusion to the patients' awakening. It was concluded, first, that the estimated concentration of propofol at extubation after long anesthesia was similar to that measured in common cases, and second, that we could reduce the emergence time at the tail end of long-sustained neurosurgery by avoiding the delay in emergence.