Abstract 2082: Serum Cystatin C is an Early Biomarker for Acute Kidney Injury following Pediatric Cardiopulmonary Bypass
Introduction: Acute kidney injury (AKI) is a frequent complication of cardiopulmonary bypass (CPB), occurring in 30% of patients. Serum creatinine (SCr), the current standard, is an inadequate marker for AKI since there is a delay before a rise in SCr occurs. Biomarkers that are sensitive and rapidly measurable could allow early intervention and improve patient outcomes. We investigated the value of serum cystatin C as an early biomarker for AKI after pediatric CPB.
Methods: We prospectively enrolled 125 children undergoing CPB. Serum samples were obtained before and at various intervals after CPB (2, 12, and 24h). Cystatin C was quantified by nephelometry (Dade-Behring BN Pro-Spec). Patients with known renal disease or receiving nephrotoxic drugs were excluded. The primary outcome was AKI, defined as a 50% or greater increase in SCr. Secondary outcomes included percent change in SCr, days in AKI, hospital length of stay, need for dialysis, and mortality. A multivariate stepwise logistic regression analysis was used to assess predictors of AKI.
Results: 45 patients (36%) developed AKI but diagnosis using SCr was delayed by 2–3 days after CPB. AKI patients had significantly longer CPB times, longer length of stay and higher mortality. In contrast to SCr, serum cystatin C levels were significantly increased in AKI patients at 12h after CPB (p<0.0001) and remained elevated at 24 hrs (p<0.0001; Table⇓). The 12h serum cystatin C strongly correlated with higher percent change in SCr and longer length of hospital stay (both p<0.005), but did not correlate with need for dialysis or mortality in the AKI patients. Adjusting for age, sex, race, previous surgery, CPB time and hospital length of stay, 12h cystatin C remained a powerful independent predictor of AKI (p<0.0001). Maximal sensitivity and specificity occurred with a cystatin C level of 1.25 mg/L with AUC of 0.89.
Conclusion: Serum cystatin C is an early, sensitive, predictive biomarker of AKI after pediatric CPB.