Objective This pilot study assesses the degree of hemolysis induced by cardiopulmonary bypass (CPB) and determines its association with acute kidney injury (AKI) in pediatric patients. Further, it evaluates the degree to which the use of urinary biomarkers neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C correlate with the presence of AKI and hemolysis following CPB. Design Prospective observational study Setting A 13-bed pediatric cardiac intensive care unit in a university hospital Patients Children undergoing cardiac surgery with the use of CPB Interventions None Measurements and Main Results Blood and urine samples were obtained at multiple time points before and after CPB. Hemolysis was assessed by measuring levels of plasma hemoglobin and haptoglobin. AKI was defined as a doubling in serum creatinine from preoperative baseline and by using the pediatric-modified RIFLE criteria. Urinary NGAL and Cystatin C levels were measured. A total of 40 patients (range: 3 days to 4.8 years) were enrolled. Plasma hemoglobin levels increased markedly on separation from CPB with a concurrent decrease in haptoglobin. This was associated with an increase in protein oxidation in the plasma. Hemolysis was more evident in younger patients with a longer duration of bypass and in those requiring a blood-primed circuit. 40% of patients had a doubling in serum creatinine and 88% of patients developed acute kidney injury when defined by the pediatric-modified RIFLE criteria. Controlling for CPB time, persistently elevated levels of plasma hemoglobin were associated with a 5 fold increase in AKI. Further, urinary NGAL measured 2 hours after separation from CPB was associated with AKI and with elevations in plasma hemoglobin. Conclusions CPB in pediatric patients results in significant hemolysis, which is associated with the development of AKI. The biomarker NGAL correlates with both AKI and hemolysis in this population.

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