Maternal and fetal effects of epinephrine in gravid ewes

Intravenous cannulation by an epidural catheter may complicate epidural anesthesia. Local anesthetic solutions containing epinephrine produce tachycardia and hypertension when given intravenously and may identify intravenous placement. The authors studied the maternal and fetal effects of intravenous epinephrine-containing solutions in ten chronically instrumented gravid ewes. While continuously monitoring maternal and fetal effects, epinephrine 5, 10, or 20 micrograms iv bolus was injected. Solutions of bupivacaine 5 mg and bupivacaine 5 mg combined with epinephrine 10 micrograms given iv were also examined. All epinephrine-containing solutions produced a significant increase (P less than 0.001) in maternal mean arterial pressure, which returned to baseline after 1 min. Maternal heart rates decreased transiently and returned to baseline after 1 min. All epinephrine-containing solutions decreased uterine blood flow (UBF) (P less than 0.001), and, for doses of 10 to 20 micrograms, this decrease lasted more than 3 min. Fetal heart rate and mean arterial blood pressure did not change following any test solution, nor did maternal or fetal arterial blood gas values. The authors conclude that small intravenous boluses of epinephrine decreased UBF in these animals.