POSTOPERATIVE PLASMA-CONCENTRATIONS AND R ESPIRATORY CHANGES AFTER INTRAOPERATIVE INFUSIONS OF FENTANYL OR SUFENTANIL

This study was designed to assess postoperatively the time course of r espiratory depression due to fentanyl (F) or sufentanil (S), as well a s the plasma concentrations. Seventy patients scheduled for orthopaedi c surgery lasting more than 3 hours were randomly assigned to two grou ps, F (n = 8) or S (n = 9). Anaesthesia was induced with etomidate (0. 3 mg . kg-1), droperidol (0.15 mg . kg-1), vecuronium (0.1 mg . kg-1), a loading dose of either F (10 mug . kg-1) or S (1 mug . kg-1), and m aintained with 60% nitrous oxide in oxygen, and an infusion of F (6 mu g . kg-1 . h-1) or S (0.6 mug . kg-1 . h-1). Mechanical ventilation wa s maintained postoperatively in the recovery room until the patient co uld be extubated. PetCO2, SpO2, f(R) and F and S plasma concentrations were assessed at the end of the opioid infusion, at extubation, every hour for the first 6 hours, and thereafter every 2 h for a further 10 and 18 h. Time to extubation was the same in both groups (301 +/- 141 and 307 +/- 148 min). At the time, plasma concentrations of F and S w ere 1.35 +/- 0.9 ng . ml-1 and 0.14 +/- 0.07 ng . ml-1 respectively. S econdary peaks in plasma concentration (78 % mean increase in comparis on to the previous figure) were observed in 6 patients in group F. No similar peaks occurred in group S. Mean elimination half-life was shor ter with sufentanil (457 +/- 130 min) than with fentanyl (325 +/- 132 min) (not significant). The results of this study suggest that sufenta nil results less frequently in postoperative secondary peaks than fent anyl.