Arteriovenous concentration differences of propofol during and after a stepdown infusion.

To compare the arterial and venous concentration differences of propofol, six healthy adult patients received a propofol infusion by the Bristol three-stage manual stepdown technique. Both the mean arterial and venous concentrations of propofol remained relatively stable during the 40-min infusion. Simultaneous blood sampling from the artery and vein during the infusion period resulted in arterial concentrations significantly higher than venous concentrations. This relationship was reversed after stopping the infusion. The mean +/- SD (range) venous to arterial concentration differences were -28.8% +/- 18.3% (-71% to 1.7%) during the infusion and 18.9% +/- 13.4% (-1.5% to 40.9%) after the infusion. We conclude that venous concentrations were not useful to estimate the arterial value during and after a stepdown propofol infusion. Arterial sampling is more appropriate in pharmacologic studies of propofol.