The effects of dopamine and epinephrine on hemodynamics and oxygen metabolism in hypoxic anesthetized piglets

Background: The most appropriate inotropic agent for use in the newborn is uncertain. Dopamine and epinephrine are commonly used, but have unknown eff ects during hypoxia and pulmonary hypertension; the effects on the splanchn ic circulation, in particular, are unclear. Methods: The effects on the systemic, pulmonary, hepatic, and mesenteric ci rculations of infusions of dopamine and epinephrine (adrenaline) were compa red in 17 newborn piglets. Three groups [control (n = 5), dopamine (n = 6) and epinephrine (n = 6)] of fentanyl anesthetized newborn piglets were inst rumented to measure cardiac index (CI), hepatic arterial and portal venous blood flow, mean systemic arterial pressure (SAP), mean pulmonary arterial pressure (PAP), and arterial, portal and mixed venous oxygen saturations. S ystemic, pulmonary, and mesenteric vascular resistance indices [systemic va scular resistance index (SVRI), pulmonary vascular resistance index (PVRI), mesenteric vascular resistance index (MVRI)], and systemic and splanchnic oxygen extraction and consumption were calculated. Alveolar hypoxia was ind uced, with arterial oxygen saturation being maintained at 55-65%. After 1 h of stabilization during hypoxia, each animal received either dopamine or e pinephrine; randomly administered doses of 2, 10, and 32 mug kg(-1) min(-1) and 0.2, 1.0, and 3.2 mug kg(-1) min(-1) respectively were infused for 1 h at each dose. Results were compared with the 1 h hypoxia values by two-way analysis of variance. Results: Epinephrine increased CI at all doses, with no significant effects on SAP and SVRI. Although epinephrine increased PAP at 3.2 mug kg(-1) min( -1), it had no effect on PVRI. Dopamine had no effect on CI, SAP, and SVRI, but increased PAP at all doses and PVRI at 32 mug kg(-1) min(-1). The SAP/ PAP ratio was decreased with 32 mug kg(-1) min(-1) dopamine, whereas epinep hrine did not affect the ratio. In the mesenteric circulation, dopamine at 32 mug kg(-1) min(-1) increased portal venous flow and total hepatic blood flow and oxygen delivery, and decreased MVRI; epinephrine had no effect on these variables. Epinephrine increased hepatic arterial flow at 0.2 mug kg( -1) min(-1); dopamine had no effect on hepatic arterial flow at any dose. D espite these hemodynamic changes, there were no differences in systemic or splanchnic oxygen extraction or consumption at any dose of dopamine or epin ephrine. Conclusions: Epinephrine is more effective than dopamine at increasing card iac output during hypoxia in this model. Although epinephrine preserves the SAP/PAP ratio, dopamine shows preferential pulmonary vasoconstriction, whi ch might be detrimental if it also occurs during the management of infants with persistent fetal circulation. Dopamine, but not epinephrine, increases portal flow and total hepatic flow during hypoxia.