Pre-operative level of FGF23 predicts severe acute kidney injury after heart surgery in children

BackgroundEarly detection of acute kidney injury (AKI) after cardiac surgery has improved recently with the discovery and validation of novel urinary biomarkers. However, objective tools to predict the risk of AKI before the insult are still missing. We tested the hypothesis that pre-operative serum fibroblast growth factor 23 (FGF23) concentrations would be elevated in children who develop AKI after heart surgery with cardiopulmonary bypass (CPB). We also compared post-operative FGF23 concentrations to other biomarkers for early detection of AKI.MethodsBlood and urine samples were collected in a prospective observational study from 83 children with congenital heart disease. Severe AKI (sAKI) development (KDIGO stages II-III) in the first seven days after surgery was the primary outcome.ResultsThirty of 76 (39.5%) and 11/76 (14.5%) of patients developed AKI and sAKI, respectively. Pre-operative serum creatinine, cystatin C, and urine biomarker concentrations did not differ between sAKI patients and controls. Pre-operative serum FGF23 levels were higher in patients who developed sAKI (median [IQR] value of 819RU/ml [397.7, 1196.8] vs. 324.3RU/ml [124.6, 679.8] (p=0.02). FGF23 12-24h after the termination of CPB was also associated with sAKI in the first week after surgery (498RU/ml [226, 928] vs. 1435RU/ml [831, 12,996]).ConclusionsPre- and post-operative FGF23 levels are higher in children who develop sAKI after cardiac surgery. We suggest FGF23 may be able to detect sub-clinical kidney injury and can be used with demographic AKI risk factors to enhance post-operative sAKI risk prediction.