DOES CONTINUOUS INTRAVENOUS-INFUSION OF LOW-CONCENTRATION EPINEPHRINEIMPAIR UTERINE BLOOD-FLOW IN PREGNANT EWES

Background and Objectives. Bolus intravenous injection of epinephrine can decrease uterine blood now. This study examined the effects of int ravenous infusion of epinephrine on uterine blood now in the gravid ew e. Methods. Maternal and fetal vascular catheters and a maternal elect romagnetic uterine artery flow probe were implanted in 10 near-term gr avid ewes. After recovery, saline, 0.125% bupivacaine, 0.125% bupivaca ine with 1:200,000 epinephrine, 0.125% bupivacaine with 1:400,000 epin ephrine, and 0.125% bupivacaine with 1:800,000 epinephrine were infuse d into the maternal superior vena cava. Drugs were infused at 10 mL/h for 30 minutes and then at 20 mL/h for an additional 30 minutes. Anima ls also received an intravenous bolus of epinephrine 15 mu g. Througho ut all infusions, maternal heart rate; systemic and pulmonary blood pr essures, uterine blood flow, cardiac output, and acid-base balance wer e measured, as well as fetal heart rate, blood pressure, and acid-base balance. Results. Epinephrine 15 mu g decreased uterine blood flow to 68 +/- 14% of baseline (mean +/- SD). Infusion of all solutions had n o effect on any measured hemodynamic variable. Conclusions. In gravid ewes, intravenous infusion of less than or equal to 1.67 mu g/min epin ephrine altered neither maternal hemodynamics nor uterine blood flow. To the extent that sheep data can be extrapolated to humans, these res ults suggest that continuous intravenous infusion of epinephrine in lo cal anesthetic solutions is safe if the epidural catheter should enter a blood vessel during the infusion.