Biomarkers for acute kidney injury: free water clearance versus pRIFLE criteria post cardiac surgery in pediatric patients

Abstract

Objective: To evaluate, as biomarker for acute kidney injury (AKI), the pediatric RIFLE criteria versus the free water clearance (TCH2O). Methods: Data from 39 previously studied patients submitted to corrective cardiac surgery for cyanotic malformations with extracorporeal circulation (ECC) were classified according to pRIFLE criteria and TCH2O. Renal function (serum creatinine and urea) was assessed once within 7 days before and twice after the surgery, 24 and 48 hours later. The pRIFLE criteria (any score alteration) and TCH2O (values more positive than -25 ml/min/1.73 m2) were compared as predictive of outcomes, such as length of stay at intensive care unit, lenght of mechanical ventilation, need for dialysis and mortality, in pediatric patients after cardiac surgery. Results: The group had a mean age of 5.5±3.1 years; weight 17.1±8.2 kg, stature 105±19 cm and time of ECC of 93 ± 34 minutes, being 20 girls (51.3%). The pRIFLE was altered in 10 cases (25.6%) in the 1st postoperative and 15 (38.4%) in the 2nd. The TCH2O was altered in 6 cases (15.4%) at both period. The outcomes of AKI at the groups are listed in table 1. pRIFLE 24h pRIFLE 48h TCH20 24h TCH20 48h normal altered p normal altered p normal altered p normal altered p Death 1/29 2/10 0.16 1/24 2/15 0.55 1/33 2/6 0.06 1/33 2/6 0.06 Peritoneal dialysis 1/29 1/10 0.45 0/24 2/15 0.14 0/33 2/60.020/33 2/60.02 ICU(days) 1.7±0.7 3.7±3.60.011.6±0.6 3.3±3.00.011.7±0.7 5.0±4.3<0.011.7±0.6 4.8±4.5<0.01 MV (days) 0.2±0.6 0.5±1.3 0.33 0.1±0.3 0.5±1.2 0.13 0.1±0.3 1.2±1.80.030.1±0.3 1.2±1.80.03 Conclusion: The TCH2O was a better predictor of the studied out-comes than pRIFLE in this sample. The renal medulla is one of the most susceptible regions to ischemic damages and the loss of urinary concentrating, demonstrated by altered TCH2O, is an early biomarker of tubular ischemia.