Brain and blood concentrations of propofol after rapid intravenous injection in sheep, and their relationships to cerebral effects

The time-course of propofol concentrations in the blood and brain following rapid administration of three doses were examined using a sheep preparation and regional pharmacokinetic techniques. These were compared to the timecourse of cerebral effects of propofol reported previously. There were marked differences between the time-course of propofol concentrations in arterial blood and the brain, with a close relationship between the time-course of brain concentrations and effects on depth of anaesthesia and CPP There was evidence that the effect of propofol on cerebral bloodflow altered its own rate of elution from the brain. Hysteresis between arterial propofol concentrations and cerebral effects following rapid IV administration therefore appears to have a pharmacokinetic basis, and conventional compartmental pharmacokinetic analysis using blood concentrations alone may fail to accurately predict the time-course of both brain propofol concentrations and depth of anaesthesia.