Effets hémodynamiques du fentanyl lors d'anesthésies à deux concentrations d'enflurane

Abstract

The cardiovascular effects of intravenous fentanyl were determined in eleven patients undergoing intra-abdominal surgical procedures under enflurane anaesthesia. The patients were curarized with pancuronium and ventilated with nitrous oxide (50 %) in oxygen. The systemic arterial pressure (P̄a) was measured by means of a left radial arterial catheter. The pulmonary artery pressure (P̄pa), the pulmonary wedge pressure (Ppw), the cardiac output, the pH and blood gases of mixed venous blood were measured by means of a thermodilution Swan-Ganz catheter. Before the surgical procedure, the measurements were carried out 10 and 20 min after the administration of 0.8 % enflurane, and 5 and 15 min after 5 μg · kg −1 intravenous fentanyl. During surgery, the measurements were repeated under 0.8 % enflurane, and then after 10 and 20 min of receiving 1.6 % enflurane, and 5 and 15 min after a second intravenous injection of fentanyl (5 μg · kg −1). Before and during surgery, the two concentrations (0.8 and 1.6 %) of enflurane had limited cardiovascular effects. Before surgery, under 0.8 % enflurane, the P̄a was steady, the heart rate (f c ) and the cardiac index (CI) decreased slightly. After the intravenous injection of 5 μg · kg −1 fentanyl, the cardiovascular depression was significant, with falls in f c (77 to 64 c · min −1 before surgery, 73 to 65 c · min −1 during surgery), CI (2.65 to 2.15 l · min −1 · m −2 before surgery, 2.50 to 2.22 l · min −1 · m −2 during surgery and P̄a (99 to 79 mmHg before surgery, 96 to 78 mmHg during surgery). Under 0.8 and 1.6 % enflurane anaesthesia, the effects of 5 μg · kg −1 fentanyl were a fall in the f c , P̄a and CI, with steady systemic vascular resistances. In patients without cardiovascular disease, the cardiovascular depression of i.v. fentanyl was of limited extent. This is probably not true in case of hypovolaemia or limited cardiovascular reserve.