Serum Lactate As Reliable Biomarker of Acute Kidney Injury in Low-risk Cardiac Surgery Patients.

Background: Cardiac surgery-associated acute kidney injury (CSA-AKI) frequently occurs in patients assessed as low-risk for developing CSA-AKI. Neutrophil GelatinaseAssociated Lipocalin (N G AL), Kidney Injury Molecule-1 (KIM-1) and lactate are promising biomarkers of CSA-AKI but have not yet been explored in low-risk patients. Aim: To evaluate urinary N G AL (uNGAL), KIM-1 and lactate as biomarkers of CSA-AKI in patients with low-risk for developing CSA-AKI. Methods: This prospective, observational study included 100 adult elective cardiac surgery patients assessed as lowrisk for developing CSA-AKI. u NGAL, KIM-1 and lactate were measured preoperatively, at the end of cardiopulmonary bypass (CPB) and 3, 12, 24 and 48 h later. Results: Fifteen patients developed CSA-AKI. Patients with CSA-AKI had significantly higher lactate but similar uN G A L and KIM-1 levels compared to patients without CSA-AKI. Unlike uN G A L and KIM-1, postoperative lactate was good biomarker of CSA-AKI with the highest odds ratio (OR) 2.7 [1.4-4.9] 24 h after CPB. Peak lactate concentration > 4 mmol/L carried dramatically higher risk for developing CSA-AKI (O R 6.3 [1.9-20.5]). Conclusions: Unlike uN G A L and KIM-1, postoperative lactate was significant independent predictor of CSA-AKI with the highest odds ratio 24 h after CPB.