Urine Output Response to a Furosemide Infusion in Infants After Cardiopulmonary Bypass as a Predictor of Acute Kidney Injury

Acute kidney injury (AKI) is a common complication in infants after cardiac surgery. Prior studies have demonstrated that urine output response to bolus dose furosemide correlates with AKI development but have excluded infants receiving a furosemide infusion. We sought to determine if urine output in response to a furosemide infusion in infants after cardiac surgery predicts AKI development. Single center retrospective cohort study of infants post cardiac surgery requiring cardiopulmonary bypass and received a post-operative furosemide infusion. A furosemide response score (FRS) (urine output [mL]/furosemide delivered [mg/kg]) was calculated. The FRS was used to determine optimal cut-offs to predict clinically significant AKI (CS-AKI), defined as stage 2 or 3 AKI. A furosemide infusion was started at a median of 9.4 h (interquartile range 6.6-13.6 h) after intensive care unit (ICU) admission in 155 infants. The post-operative incidence of AKI was 76.8%, with 44.5% having CS-AKI. The optimal FRS cut-off to correlate with AKI was 11.3 mL/mg/kg at 4 h (area under the curve [AUC] = 0.75), 25.5 mL/mg/kg at 10 h (AUC = 0.70), and 53.3 mL/mg/kg at 24 h (AUC = 0.70) post-infusion initiation, and independently associated with the development of AKI. Lower FRS also correlated with increased mechanical ventilation days and ICU/hospital length of stay. Urine output in response to a furosemide infusion in infants following cardiac surgery is associated with post-operative CS-AKI. The FRS can be used to predict AKI and potentially improve hemodynamics while minimizing risks.