Novel Markers Neutrophil gelatinase-associated lipocalin (NGAL) and Cystatin C in determining Acute Kidney Injury after Heart Operations using Cardiopulmonary Bypass
Jurij M. Kališnik, MD, PhD1, Eva Hrovat, MD1, Alenka Hrastovec, MD1, Aleš Jerin, PhD1, Milan Skitek, PhD1, Janez Žibert, PhD2, Borut Geršak, MD, PhD1.
1University Medical Center, Ljubljana, Slovenia, 2Faculty of Health Sciences, Ljubljana, Slovenia.
OBJECTIVE: Acute kidney injury (AKI) represents frequent complication after cardiac surgery using cardiopulmonary bypass (CPB). The assessment of AKI rests on creatinine levels, which are dependent on many parameters, causing relatively late and less reliable AKI recognition after surgery. We tested the utility of neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C (CysC) for determination of AKI after cardiac surgery using CPB.
METHODS: Sixty patients participated in the study, 48 met the inclusion criteria. Arterial blood samples collected after induction of general anaesthesia were used as baseline, further sampling occurred at CPB termination, 2 hours after CPB, on the first and second day after surgery. Statistical analyses were performed using Student t-test, p value <0,05 was considered significant.
RESULTS: According to AKIN classification 18 patients (38%) developed AKI (AKI group) and 30 did not (nonAKI group). Groups were similar regarding demographics and operative characteristics, except for age and Euroscore II in AKI group (77,0 ± 7,1 vs. 70,3 ± 11,4 yrs; p=0,03, 3,32 ± 2,26 vs. 2,18 ± 1,62; p=0,05, respectively). Preoperative creatinine and glomerular filtration rate were similar between two groups (p=0,11, p=0,36, respectively). Creatinine increased significantly on the first postoperative day, whilst NGAL tended to be higher at CPB termination (208,2 ± 81,6 vs. 172,5 ± 59,1μg/l; p=0,09) and remained elevated consistently thereafter (176,2 ± 71,6 vs. 139,4 ± 47,2 μg/l; p=0,04, 133,9 ± 62,3 vs. 69,2 ± 37,9 μg/l; p=0,001, 151,4 ± 106,0 vs. 68,4 ± 40,6 μg/l; p=0,005, respectively) in AKI group. CysC started to rise 2 hours after CPB (920,3 ± 253,4 vs. 765,9 ± 270,2 μg/l; p=0,06) and exhibited consistently higher levels over time in AKI group (1344,4 ± 581,2 vs. 865,8 ± 260,5 μg/l; p=0,003, 1572,2 ± 565,1 vs. 877,0 ± 393,4 μg/l; p<0,001, respectively).
CONCLUSIONS: Both novel markers NGAL and CysC proved efficient in differentiating between AKI and non-AKI group after heart surgery using CPB. While the postoperative peak of serum NGAL occurred as early as immediately after separating from CPB, CysC reached maximal values later in postoperative course, similarly to creatinine only on the first postoperative day.
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