The effect of dopamine on glomerular filtration rate in normotensive, oliguric premature neonates.

We examined the effect of dopamine on glomerular filtration rate (GFR) at infusion rates of 0.5, 2.5, and 7.5 micro g/kg per min in 15 premature neonates. Study infants (mean gestational age 34+/-2 weeks, mean birth weight 2.43+/-0.6 kg) had respiratory distress, were normotensive, and had a low urine output (0.9+/-0.1 ml/kg per hour). GFR was determined by the plasma clearance of inulin after a single bolus injection (200 mg/kg). Four hours after inulin administration, dopamine infusion was begun and continued over 6 h. GFR was estimated before and after beginning the dopamine infusions from the slope of the log of plasma inulin concentration versus time. Gestational age, weight, and baseline GFR were similar in all three groups. With a dopamine infusion rate of 0.5 micro g/kg per min there were no changes in GFR, urine output, heart rate, or blood pressure. At an infusion rate of 7.5 micro g/kg per min there was no change in GFR, although urine output, heart rate, and blood pressure all increased. At 2.5 micro g/kg per min there were significant increases in GFR and urine output, with no changes in blood pressure or heart rate. In oliguric, non-hypotensive neonates, GFR increased significantly at 2.5 micro g/kg per min of dopamine. This probably reflects the effects of afferent vasodilatation and may be important clinically when enhancement of GFR is the major treatment objective.