Abstract 12488: Serum Cystatin C is an Early Predictor of Acute Renal Injury in Infants After Cardiac Surgery With Cardiopulmonary Bypass

Abstract

Introduction: Acute kidney injury (AKI) following infant cardiac surgery is common, with increased morbidity and mortality. Changes in urine output and/or serum creatinine (SCr) are unreliable in the detection of AKI as defined by the Kidney Disease Improving Global Outcomes (KDIGO) guidelines, and lag behind onset of renal injury. Serum Cystatin C (SCC) has been used as a biomarker of AKI in adults and older children. If SCC predicts AKI in infants following cardiopulmonary bypass (CPB) is unknown. Hypothesis: SCC is an early biomarker of AKI following infant cardiac surgery requiring CPB. Methods: 42 infants (< 1 year of age) were prospectively enrolled when presenting for cardiac surgery requiring CPB. SCC and SCr were measured at baseline (pre-operatively), and at 12, 24, and 48 hours following CPB initiation, and changes in SCC and SCr compared to baseline (ΔSCC and ΔSCr, respectively) were calculated. AKI was defined using KDIGO guidelines, as an increase in SCr ≥ 50% and/or a urine output < 0.5mL/kg/hr for ≥ 6-12 consecutive hours in the first 3 post-operative days. Subjects were divided in 2 groups: AKI and non-AKI. Receiver Operating Characteristic (ROC) curves were utilized to predict AKI based on ΔSCC and ΔSCr, and the area under the curve (AUC) was quantified. Results: AKI occurred in 17 (40.4%) subjects. Baseline SCC and SCr measurements were similar between groups, as were age, gender, weight, and CPB time. Post-operative SCC values decreased from baseline, suggesting volume overload. While SCC concentrations did not differ significantly between the 2 groups, ΔSCC measurements were significantly different in those with AKI at 12 hours (0.2 ± 0.3 vs 0.4 ± 0.2; p < 0.01) and remained different at 24 hours (0.1 ± 0.3 vs 0.3 ± 0.2; p = 0.02). ΔSCr measurements were significantly greater in the AKI group at 24 hours (0.1 ± 0.1 vs 0.0 ± 0.1; p < 0.01) and 48 hours (0.1 ± 0.1 vs. 0.0 ± 0.1; p < 0.01) but not at 12 hours. ROC curves demonstrated that both the ΔSCC at 12 hours (AUC = 0.72; p = 0.02) and the ΔSCr at 24 hours (AUC= 0.78; p < 0.01) predicted AKI. Conclusions: The 12 hour ΔSCC predicts AKI in infants after cardiac surgery, and correlated with a rise in ΔSCr the following day. Earlier detection of AKI would allow earlier post-operative intervention to mitigate renal injury in infants.