EFFECTS OF PROPOFOL AND THIOPENTAL ON MATERNAL AND FETAL CARDIOVASCULAR AND ACID-BASE VARIABLES IN THE PREGNANT EWE

Background. The effects of propofol on uterine blood flow are not understood well. This is a relatively new agent that is finding increased use for nonobstetric surgical procedures during pregnancy and induction of anesthesia for cesarean section. Methods. The effects of induction and maintenance of anesthesia with propofol were studied on maternal and fetal cardiovascular and acid-base variables in a chronically instrumented pregnant sheep model. Anesthesia was induced with a 2 mg/kg bolus of propofol and maintained with of one of three continuous infusions: 150, 300, and 450 mug . kg-1 . min-1. The control group received thiopental for induction, and anesthesia was maintained with isoflurane. Results. The use of propofol did not adversely affect maternal or fetal mean arterial pressure, heart rate, or base excess, fetal heart rate variability, or uterine blood flow. Uterine blood flow transiently decreased during induction and intubation with thiopental but remained stable during induction with propofol. However, administration of succinycholine for intubation in the presence of propofol resulted in a transient, but severe, maternal bradycardia. Continuous infusion of 300 mug . kg-1 . min-1 of propofol appeared to provide satisfactory anesthesia in the ewe. Conclusions. Assuming the applicability of ovine data to humans, these findings suggest that induction and maintenance of anesthesia with propofol and 50% nitrous oxide in oxygen has no adverse fetal effects but warrants caution because of the potential risk of severe maternal bradycardia during induction of anesthesia using the combination of propofol and succinylcholine.