Added value of serum-cystatin C in cardiac surgery patients with cpb developing AKI

Abstract

Aims. AKI is common after cardiac surgery involving CPB. S-cystatin C is a novel early biomarker for AKI awaiting validation in this setting. Goal was to develop a clinical predictive model for AKI and test the added value of s-cystatin C within the first 24 hrs post-op. Methods. 259 patients were enrolled. Patients with severe pre-existing renal insufficiency were excluded (eGFR<15 ml/min). Urine and blood samples were obtained immediately before initiation of CPB, at 3h, 6h, 12h and 24h post-op. Patients were retrospectively divided into 2 groups, AKI (n=84)(32%) and non-AKI (n=175)(68%), based on the AKIN criteria (increase in s-Creat ≥ 0.3 mg/dl or ≥ 50% compared to baseline within 48h or reduction in Urine output <0.5 ml/kg/h for more than 6h). Statistical analysis to determine which clinical factors were predictive for AKI was performed (diabetes was not included). Subsequent analysis of the added value of serum-cystatin C to this model. Results. Only duration of CPB, BMI and pre-op eGFR had predictive value in the clinical setting with the following combined AUC scores for AKI: 0.737 (3h post-op), 0.767 (6h post-op), 0.745 (12h post-op) and 0.755 (24h post-op). Addition of s-cystatin C increased the discriminative power at time points preop, 3h post-op, 6h post-op and 12h post-op (AUC scores of 0.776, 0.823 and 0.798 resp, all p<0.05 compared to clinical model alone). Conclusion. Addition of s-cystatin C to a predictive clinical model for AKI has significant added value.