Arterial and jugular venous bulb blood propofol concentrations during induction of anesthesia

The aim of this study was to show that blood propofol concentrations at loss of consciousness vary with the rate of administration. Eighteen patients were allocated to receive a propofol infusion at 6 or 12 mg.kg-1.h-1 (approximately 8 and 15 mg/min) for induction of anesthesia. Propofol concentrations were analyzed from simultaneous arterial and jugular bulb venous blood samples. There were no significant differences in the dose of propofol administered to induce anesthesia (0.52 mg/kg both groups). However there were significant differences between the groups in the mean induction times (309 and 156 s), and in median arterial and venous concentrations at induction. Arterial concentrations were 1.93 and 2.70 and venous 1.11 and 1.51 micrograms/mL. There were no significant differences between the groups in the area between the arterial and venous time concentration curves from start of infusion to loss of consciousness (3.14 and 3.05 micrograms.mL-1.min-1). This study confirms that a target blood concentration of propofol cannot be identified with loss of consciousness under nonsteady state conditions. Both arterial and venous blood propofol concentrations at loss of consciousness depend on the rate of administration.