ObjectivesTo study the acute hemodynamic effects of furosemide in critically ill pediatric patients, the temporal relationship between hemodynamic changes and changes in neuroendocrine axis, and the temporal relationship between hemodynamic changes and urine output.DesignProspective study.SettingPediatric intensive care unit in a tertiary care university center.PatientsFourteen critically ill pediatric patients who clinically required diuretic therapy.InterventionsBefore and after furosemide administration, hemodynamic and neurohormonal measurements were taken.Measurements and Main ResultsHemodynamic and neurohormonal responses to acute diuretic therapy were measured in 14 pediatric patients treated with furosemide (1 mg/kg/dose). Cardiac index deteriorated by 10 mins after drug administration (minus 9.4 plus minus 3.9%, p less than .05) and was associated with an increase in systemic vascular resistance (17.1 plus minus 4.8%, p less than .05). There was a subsequent increase in cardiac index (20 plus minus 4.9%, p less than .05) at 30 mins, with a decrease in systemic vascular resistance (minus 11.5 plus minus 5.2%, p less than .05). These hemodynamic changes were associated with marked increases in renin and norepinephrine concentrations and an increase in urinary prostaglandin release. The hemodynamic and neurohormonal effects had their onset before maximum diuresis.ConclusionIntravenous furosemide administration in acutely ill pediatric patients results in an acute but transient deterioration in cardiac function that appears to parallel the neuroendocrine changes rather than the acute diuresis.(Crit Care Med 1996; 24:398-402)