Objective:Aminophylline has not been studied as an adjunct diuretic in critically ill children. Our purpose was to evaluate its use in the treatment of fluid overload in these patients.Design:Open, controlled clinical trial.Setting:Pediatric intensive care unit.Patients:Study subjects ranged from 2-46 months of age, were fluid overloaded, and were receiving a continuous infusion of furosemide (≥6 mg/kg/day). Patients with hemodynamic instability or liver dysfunction were excluded.Interventions:A single dose of aminophylline (6 mg/kg) was given after establishing baseline values. There were no additional diuretics or changes in vasoactive agents during the study.Measurements and Main Results:Urine output, creatinine clearance, and sodium and potassium excretion were measured before and after administration of the aminophylline bolus. Heart rate and mean arterial pressure (mm Hg) were recorded hourly. Urine output increased by >80% (p< .01) during the first 2 hrs after administration of the aminophylline bolus and then returned to baseline by 4 to 6 hrs. The change in urine output is consistent with the pharmacokinetics of aminophylline. Heart rate and mean arterial pressure exhibited a change of <10% from baseline.Conclusions:These results suggest that aminophylline is an effective adjunct to furosemide in increasing diuresis in critically ill children with fluid overload. The increased diuresis can be accomplished without increased risk if drug levels are adequately monitored.