Renal effects of low to moderate doses of dopamine in newborn piglets

Abstract

Purpose : Administration of dopamine to adult animal and human subjects results in increased renal blood flow, and it may also enhance the glomerular filtration rate. However, renal hemodynamic effects of exogenous dopamine in the neonate are unclear. In this study, we examined the renal actions of low to moderate doses of exogenous dopamine in newborn piglets. Methods : The animals were anesthetized, catheterized for vascular access and urine collection, and assigned randomly to a control group or treatment groups receiving dopamine infusion at 2, 5, or 10 μg/kg/min. Data were collected at baseline, during dopamine infusion, and 1 hour after cessation of infusion. Mean arterial blood pressure (MAP) and heart rate (HR) were monitored. Glomerular filtration rate (GFR), cardiac index (Cl), and renal blood flow (RBF) were determined. Fractional excretion of sodium (FENa) was calculated. Results : Dopamine did not alter renal blood flow nor did it significantly alter Cl in spite of a modest increase in heart rate and mean arterial blood pressure. There was a statistically significant increase in GFR at 10 μg/kg/min and in FENa at all doses. Conclusions : Low doses of dopamine produce significant natriuresis probably by direct action on renal tubules and at moderate doses via, both, increase in GFR and a direct tubular effect. Low and moderate doses of dopamine do not increase RBF as seen in adult animals, possibly because of immaturity of dopaminergic receptors in newborn piglets.