CONCENTRATION-EFFECT RELATIONSHIPS OF PROPOFOL AFTER TOTAL INTRAVENOUS ANESTHESIA

To evaluate the concentration-effect relationships of propofol during recovery after total intravenous anesthesia, 20 female patients underg oing lower abdominal surgery were studied. In 10 patients (Group B) th e propofol infusion was supplemented with an epidural block with bupiv acaine to evaluate the relation between the blood concentration of pro pofol and various pharmacodynamic end-points. The remaining 10 patient s (Group A) received an alfentanil infusion intravenously instead of t he epidural block to assess the dynamic interactions of alfentanil and propofol. Post-operative performances (drowsiness, amnesia, cooperati on, and orientation) were evaluated by means of scoring scales. Critic al flicker fusion threshold (CFF) also was used to assess the level of postoperative alertness. A propofol blood concentration of 2.5 mug/mL was required for satisfactory hypnosis during surgery and at 0.8 +/- 0.4 mug/mL, the patients were considered fully awake. A concomitant al fentanil infusion reduced the propofol concentration required by 0.2-0 .4 mug/mL for the same degree of effect. Rapid recovery was seen in al l patients, but in the group receiving alfentanil infusion there was a shift to the left of the concentration-effect curve in regard to drow siness and a statistically significant prolongation of recovery by CFF -measurement which suggests a possible dynamic interaction with alfent anil. We conclude that there is a good correlation between the blood c oncentration of propofol and the pharmacodynamic responses during reco very.