AMRINONE LOADING DURING CARDIOPULMONARY BYPASS IN NEONATES, INFANTS, AND CHILDREN

Objectives: To determine whether amrinone is bound to cardiopulmonary bypass circuits. When amrinone is administered to children during card iopulmonary bypass, determine whether measured amrinone concentrations differ from those predicted based on a reported volume of distributio n of 1.6 L/kg. Design: In vitro study: Uptake of amrinone by cardiopul monary bypass circuits was determined. Clinical study: Prospective, op en label investigation. Setting: University-affiliate tertiary childre n's hospital. Participants: Clinical study: 27 children participated, including 5 neonates and 9 infants. Interventions: In vitro study: Was te blood was circulated within seven-pediatric cardiopulmonary circuit s. Amrinone was administered, and blood was serially assayed for amrin one levels. Clinical study: Amrinone (mean dose 4.9 mg/kg) was loaded during cardiopulmonary bypass and amrinone concentrations in pump bloo d were determined at termination of bypass. Amrinone measured by high- performance liquid chromatography. Measurements and Main Results: Card iopulmonary bypass circuit uptake reduced amrinone concentrations to 7 9% of predicted. After correcting for circuit uptake, serum amrinone r evels in patients were significantly higher than predicted. The levels , expressed in the ratio of measured: predicted amrinone concentration , did not differ among neonates, infants, and children older than 1 ye ar of age. Conclusions: When amrinone is administered to children duri ng cardiopulmonary bypass, about 20% of the dose becomes bound to the circuit. Available drug is distributed within a smaller Volume than pr edicted. This may be the consequence of the physiologic perturbations of hypothermic cardiopulmonary bypass. Copyright (C) 1995 by W.B. Saun ders Company