Commentary: Predicting acute kidney injury in pediatric cardiac surgery

Abstract

Acute kidney injury (AKI) is a frequent complication of congenital heart surgery that is associated with increased morbidity in the acute period. Early diagnosis is critical to manage fluid overload, prevent additional nephrotoxic insults, and maintain frequently used drugs such as milrinone and antibiotics within therapeutic range. A rise in serum creatinine is often delayed by 1-3 days after renal injury. In this edition of The Journal of Thoracic and Cardiovascular Surgery, Penk and colleagues 1 have authored a multiinstitutional retrospective analysis entitled ''Furosemide Response Predicts Acute Kidney Injury in Children Following Cardiac Surgery.'' Their major findings were that urinary flow rate in response to furosemide was significantly lower through 2 and 6 hours in the patients who had development of AKI according to the creatinine-defined Kidney Disease Improving Global Outcomes criteria. Lower urinary flow rate also led to an increased length of stay, independent of AKI. In their study, despite development of AKI in 33% of patients, no patient required renal replacement therapy, and mortality was low. In addition, Penk and colleagues 1 present a receiving operating characteristic analysis for prediction of severe AKI with ideal cutoff points. This is a multi-institutional study composed of patients with complex congenital operations, across a wide age range. Because of its retrospective nature, however, the dose of furosemide was not standardized, and the timing of administration varied widely (median, 14.0 hours; interquartile range, 9.5-19.3). Furthermore, Penk and colleagues 1 could not control for patients' hemodynamics and fluid status at the time of furosemide administration or for variations in perfusion strategies. This publication, as well as 2 recent single-center retrospective studies in neonates and infants referenced therein, all demonstrated similar associations between AKI with lower urinary flow rate after furosemide administration. Nevertheless, there are important differences between their methodologies and that of the standardized furosemide stress test, which has been validated prospectively in adult critically ill patients. 2 An early predictor for AKI would be clinically relevant in pediatric cardiac surgery for postoperative outcomes.