Dopamine clearance in critically ill infants and children: effect of age and organ system dysfunction.

To learn if there are age-related differences in the pharmacokinetic behavior of dopamine, plasma dopamine clearance was determined in 27 acutely ill infants and children who were receiving a continuous intravenous infusion of the drug. Steady-state clearance was calculated from dopamine concentration in arterial blood. Dopamine clearance was 60.7 +/- 28.1 ml/kg/min. The age of the patient exerted an effect on clearance of dopamine (r = -0.63; p less than 0.05), and dopamine clearance was nearly twice as rapid in children younger than 2 years as it was in older children (82.3 +/- 27.7 ml/kg/min versus 45.9 +/- 17.0 mg/kg/min). Conjugated bilirubin exerted an age-independent effect on clearance of dopamine; clearance was 44.8 +/- 28.6 ml/kg/min in children with abnormal conjugated bilirubin (greater than or equal to 0.9 mg/dl) and 70.1 +/- 2.56 ml/kg/min in children with normal conjugated bilirubin (less than 0.9 mg/dl). Clearance was lowest (29.8 +/- 5.7 ml/kg/min) in the four children who had both hepatic and renal dysfunction. Age is an important determinant of dopamine clearance, explaining in part the clinical observation that infants and young children require higher infusion rates.