EFFECTS OF LOW-DOSE DOPAMINE INFUSION ON CARDIOVASCULAR AND RENAL FUNCTIONS, CEREBRAL BLOOD-FLOW, AND PLASMA-CATECHOLAMINE LEVELS IN SICK PRETERM NEONATES

Effects of 2 and 4 mug/kg/min dopamine infusion on cardiovascular and renal functions, cerebral blood flow (CBF) and plasma catecholamine levels were studied in sick preterm neonates during the first four days of life. Preterm infants were found to have an enhanced responsiveness to the pressor effects of dopamine during this period. Comparison of the renal effects of 2 and 4 mug/kg/min dopamine in 61 preterm infants indicate that 2 mug/kg/min dopamine induces maximum diuresis and natriuresis during the first day of life provided that systemic blood pressure is within the predicted normal range. Although administration of 4 mug/kg/min dopamine induces further increases in blood pressure and glomerular filtration rate, urine output and sodium excretion remain similar to that on 2 mug/kg/min of the drug. These findings demonstrate that the direct tubular effects of dopamine play an important role in the diuretic and natriuretic action of the drug in the one-day old preterm infant. In rive preterm neonates, changes in CBF transiently paralleled the dopamine-induced alterations in systemic blood pressure indicating that autoregulation of CBF is impaired but not completely ineffective in the one-day old preterm infant. In eight term neonates, increases in blood pressure had no effect on CBF. Measurements of plasma dopamine and norepinephrine levels in 14 preterm neonates and five children suggest that decreased metabolism of dopamine may contribute to the enhanced pressor responsiveness to dopamine in sick preterm infants. Based on these findings, we propose that dopamine should be started at 2 mug/kg/min in the hypotensive and/or oliguric preterm infant, and that the dose should be increased in a step-wise manner tailored to the cardiovascular and renal response to the patient.