Incidence and outcome of acute kidney injury after open heart surgery in children

Abstract

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 affect kidney and contribute to the acute kidney injury (AKI). Objective. To evaluate incidence and outcome of AKI in children undergoing open heart surgery. Methods. We conducted a prospective, non-randomized observational study at the tertiary care of the University Children’s Hospital Pediatric ICU. We enrolled 30 patients, 12 boys and 18 girls with CHD. Their median body weight was 6.8 kg (IQR 5.2 < 8.2 kg) and the median age was 7 months (IQR 5  <  10  months). SCr was determined and preoperative and postoperative creatinine clearance (ClCr) was estimated using the Schwarz formula. During surgical repair and till the end of the first 24  hours urine was collected to measure ClCr, using the difference in urine (UCr) and SCr concentrations. Urine output, body temperature, duration of aortic cross clamping and cardiopulmonary bypass were 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. Intraoperative SCr rised to 35 µmol/l (IQR 27.5 < 50.5) vs. preoperative SCr 29  µmol/l (IQR 24  <  32.9), P  <  0.0001. GFR declined from pre­ operative 98.4 ml/min/1.73 m2 (IQR 89.6 < 123.04) to intraoperative 39.8 ml/min/1.73 m2 (IQR 24.9 < 65.5), P < 0.0001. Observed incidence of AKI was 30% (9/30). We observed statistically significant (P = 0.006) inverse correlation (r = 0.522) between CPB time and ClCr. Conclusions. Open heart surgery in children has severe, but transient effect on expression of renal biomarkers. Observed incidence of AKI was 30% (9 from 30 of our patients). Before discharge from the hospital both biomarkers returned to normal values.