[Association between urinary neutrophil gelatinase-associated lipocalin and acute kidney injury after cardiac surgery].

OBJECTIVE: To test the hypothesis that Neutrophil gelatinase-associated lipocalin (NGAL) is an early biomarker for acute kidney injury (AKI) in patients after cardiac surgery. METHODS: 33 cases undergoing cardiac surgery were divided into AKI group and Non-AKI group according to the AKI criteria. The concentration of urine NGAL at different time points were measured. RESULTS: (1) Nine of 33 cases (27%) developed postoperative AKI, but diagnosis with serum creatinine was only 12-48 hours after cardiac surgery. (2)Urinary concentrations of NGAL at 2 h after cardiac surgery in patients who did not developed AKI were significantly higher compared with those of preoperative (P < 0.001). Urinary concentrations of NGAL at 2 h and 4 h after cardiac surgery in patients who developed AKI were significantly higher compared with those of preoperative (P < 0.001). (3) The mean urinary NGAL concentrations in patients who developed AKI were significantly higher after surgery compared with patients who did not develop AKI (P < 0.01). (4) Urinary concentrations of NGAL/Ucr at 2 h and 4 h after cardiac surgery in patients who did not developed AKI were significantly higher compared with those of preoperative (P < 0.05). Urinary concentrations of NGAL/Ucr at 2 h and 4 h after cardiac surgery in patients who developed AKI were significantly higher compared with those of preoperative (P < 0.01). (The mean urinary concentrations of NGAL/Ucr in patients who developed AKI were significantly higher after surgery compared with patients who did not develop AKI (P < 0.01). (6) For concentrations in urine of NGAL at 2 h after surgery, sensitivity was 0.7125, and specificity was 0.7307 for a cutoff value of 250 microg/L. For concentrations in urine of NGAL/Ucr at 2 h after surgery, sensitivity was 0.8127, and specificity was 0.7839 for a cutoff value of 250 microg/mmol. (7) Urinary concentrations of NGAL at 2 h after cardiac surgery was significantly associated with serum creatinine 12 h postoperative (R = 0.638, P < 0.05). CONCLUSIONS: The incidence of AKI in patients after cardiac surgery is high, which accounted for 27%. The amount of NGAL and NGAL/Ucr in urine at 2 h after cardiac surgery were the powerful independent predictor of acute renal injury and urine concentrations of NGAL/Ucr is more sensitive.