Open Heart Surgery Associated Acute Kidney Injury in Children

Introduction. Cardiac surgery with cardiopulmonary bypass (CPB) is commonly perceived as a risk factor for decline in renal function. Hypothermia, hypoxia, hypotension, non-pulsatile blood flow during CPB, use of ACE inhibitors, inotropic and (or) vasoactive support affects kidney and contributes to the acute kidney injury (AKI).

Aim of the study. The purpose of this study was to evaluate the incidence, severity and outcome of CPB related AKI in children after open heart surgery.

Materials and methods. We conducted prospective, non-randomized observational study at the tertiary care University Children’s Hospital Pediatric ICU. We enrolled 30 patients, 12 boys and 18 girls with congenital heart disease (CHD). Their median body weight was 6,8 kg, (IQR 5,2<8,2 kg) and median age 7 months (IQR 5<10 months). SCr was determined and preoperative and postoperative creatinine clearance (ClCr) was estimated using Schwarz formula (eClCr). During surgical repair and till the end of the first 12 postoperative hours urine was collected to measure ClCr, using the difference in urine (UCr) and SCr concentrations (mClCr). Urine output, body temperature, duration of aortic cross clamping and cardiopulmonary bypass was recorded.

Results. Median intraoperative urine output was 2,4 ml/kg/h (IQR 1,29<3,15 ml/kg/h). Median CPB time was 147 min., (IQR 116,75<205 min.), median aortic cross-clamping time was 95 min., (IQR 70,5<133 min.), cooling during CPB to 29,75°C. Postoperative SCr increased to 35 μmol/l (IQR 27,5<50,5 μmol/l) vs. preoperative SCr 29 μmol/l (IQR 24<32,9 μmol/l), P<0,0001. GFR declined from preoperative 98,4 ml/min./1,73 m2 (IQR 89,6<123,04) to postoperative 80,98 ml/min./1,73 m2, (IQR 60,73<97,97 ml/min./1,73 m2), P<0,0001. We find statistically significant difference (P=0,042) in measured 39,88 ml/min./1,73 m2 (IQR 21,96<67,82 ml/min./1,73 m2) versus estimated ClCr (eClCr) 80,98 ml/min./1,73 m2, (IQR 60,73<97,97 ml/min./1,73 m2). Observed prevalence of AKI was 46,6% (14/30 patients met KDIGO criteria for AKI). Conclusions.Open heart surgery in children has severe, but transient effect on expression of renal biomarkers. There was a marked difference between measured and estimated ClCr in our patients. Observed incidence of AKI was 46,6% (14 patients met KDIGO criteria of AKI from 30 of our patients). Before discharge from the hospital both biomarkers returned to normal values.