EFFECTS OF A CONTINUOUS EPINEPHRINE INFUSION ON REGIONAL BLOOD-FLOW IN AWAKE NEWBORN PIGLETS

Objective: To determine the effects of a continuous epinephrine infusi on on renal and mesenteric blood flow in both healthy newborn piglets and animals subjected to hemorrhagic shock. Methods: Superior mesenter ic artery (SMA) and left renal artery ultrasonic flow probes were impl anted into 16 1- to 3-day-old piglets. Two days later, the effects of epinephrine on SMA and renal blood flow, mean arterial pressure (MAP) and central venous pressure were measured in conscious, non-sedated no rmovolemic piglets. Epinephrine doses of 0.2, 0.4, 0.8, 1.6 and 3.2 mu g/kg.min were used in random order. Piglets were subsequently hemorrh aged (20 ml/kg) to mild hypotension and again received epinephrine inf usion in the same doses. Results: Doses of epinephrine less than 3.2 m u g/kg.min had no significant effects on renal or mesenteric arterial flow. At 3.2 mu g/kg.min of epinephrine during normovolemia, there was a significant decrease in SMA blood flow (34% [SD 42], p < 0.05) and increase in SMA vascular resistance (147% [SD 114], p < 0.05). Similar results were shown during hypovolemia, SMA flow decreased by 32% (SD 33), and SMA vascular resistance increased by 220.3% (SD 177). At 3.2 mu g/kg.min renal artery flow decreased by 43% (SD 21) during normovol emia and a similar decrease occurred during hypovolemia, 37% (SD 31). Renal vascular resistance increased by about 200% at this dose (normov olemia 211% [SD 185], hypovolemia 186% [SD 150], p < 0.01). Low-to-mod erate dose epinephrine caused no significant change in SMA or renal bl ood flow. During hypovolemia low dose epinephrine infusion was associa ted with a trend to increased SMA blood flow. Conclusion: Low-dose epi nephrine does not cause vasoconstriction in the renal or mesenteric ci rculations during normovolemia or hypovolemia. High doses of epinephri ne above 1.6 mu g/kg.min may cause renal or mesenteric ischemia, in ei ther the normovolemic or hypovolemic neonate.