THE ARTERIAL BLOOD PROPOFOL CONCENTRATION PREVENTING MOVEMENT IN 50-PERCENT OF HEALTHY WOMEN AFTER SKIN INCISION

To target appropriate drug concentrations and to facilitate comparison s between drugs, the potency of propofol must be firmly established. W e therefore deter mined the arterial blood propofol concentration prev enting movement in 50% of patients after skin incision and the ability of arterial blood pressure and heart rate to predict movement after i ncision. Fifteen healthy women scheduled for breast surgery were rando mly assigned to computer-targeted propofol blood concentrations. No ot her drugs were administered. Fifteen minutes after starting the propof ol infusion, a 5-cm skin incision was made. Patients were observed for gross purposeful movement for 1 min. Arterial blood was sampled for p ropofol to confirm steady-state blood concentrations. Arterial blood p ressure and heart rate were measured noninvasively. Logistic regressio n was used to calculate the propofol blood concentrations and arterial blood pressures at which 50% and 95% of patients did not move after s kin incision (CP50 and CP95, MABP(50) and MABP(95), respectively). The CP50 and CP95 values for propofol were 14.3 +/- 1.6 mu g/mL (mean +/- SE) and 20.6 mu g/mL, respectively. The MABP(50) and MABP(95) values were 63 +/- 4 mm Hg and 43 mm Hg, respectively. Heart rate did not dif fer significantly in patients who moved and who did not move, Propofol blood concentrations required to prevent movement in most patients re sulted in significant arterial hypotension.