The Maternal and Fetal Cardiovascular Effects of Epidural Fentanyl in the Sheep Model

Since the demonstration of opiate receptors in the spinal cord in the mid-1970s, investigators have been looking for the most effective epidural narcotic. With the use of the chronically catheterized maternal sheep model, we injected two different doses of preservative-free fentanyl (50 and 100 μg) into the epidural space. No statistically significant changes were observed, either in maternal or fetal arterial pressure and acid-base status or in maternal central venous pressure, systemic and pulmonary vascular resistance, cardiac output, and intrauterine pressure (p > 0.05). With a dose of 50 μg of fentanyl, maternal levels of fentanyl peaked at 60 minutes (50 pg/ml) and the fetal levels of fentanyl peaked at 45 minutes (20 pg/ml). With the 100 μg dose of fentanyl, maternal levels of fentanyl peaked at 45 minutes (230 pg/ml) and the fetal levels peaked at 15 minutes (110 pg/ml). We conclude that the injection of 50 and 100 μg of fentanyl into the maternal epidural space has no adverse effects on mother or fetus in the sheep model.