Perioperative renal oximetry via near-infrared spectroscopy for prediction of acute kidney injury in infants undergoing congenital heart surgery: An observational study

Objective: Acute kidney injury (AKI) is a frequent complication after pediatric cardiac surgery with cardiopulmonary bypass (CPB). Serum creatinine and biomarkers cannot be continuously monitored. Near- infrared spectroscopy (NIRS) allows continuous assessment of regional tissue oximetry (rSO2) and reflects renal rSO2 when placed on flank overlying kidney. The aim of our study was to establish whether there is a relation between rSO2 values measured by NIRS in early AKI in infants following cardiac surgery. Methods: Renal NIRS was monitored continuously post-operatively for first 24 hours in sixty infants undergoing cardiac surgery. Patients were divided in AKI (n=21) and non-AKI (n=39) groups. Mean blood pressure, oxygen saturation, central venous oxygen saturation, serum lactate, serum uric acid, blood urea, fluid intake and urine output were measured at various time points. Poor outcome was defined as length of intensive care unit and hospital stays and raised mortality. Results: 21 patients developed AKI (35%) by AKIN criteria. AKI group patients had significantly prolonged CPB time (p=0.03) and aortic cross-clamp time (p<0.001) compared to non-AKI group patients. There was significant increase in creatinine at 24 hours (p<0.001) in AKI group compared to non-AKI group. AKI patients had significantly lower mean renal rSo2 post-operatively at 8 hours (76.95 (8.65) vs 81.23 (10.44), p=0.044) and 12 hours (73.95 (9.41 vs 81.49 (8.1), p=0.006). Poor outcome parameters (long ICU and hospital stay, death) were significantly more frequent in AKI group than in non-AKI group (all p<0.05). Conclusion: Continuous monitoring of renal rSO2 can predict subclinical AKI in early phase, allowing early therapeutic intervention before further progression of AKI.