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Early determination of acute kidney injury after aortic valve replacement surgery by neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C
Alenka Hrastovec, MD1, Aleš Jerin, PhD2, Janez Žibert, PhD3, Milan Skitek, PhD2, Tomislav Klokočovnik, MD, PhD4, Jurij Matija Kališnik, MD, PhD4.
1Department of Anaesthesiology, University Medical Centre, Ljubljana, Slovenia, 2Institute of Clinical Chemistry and Biochemistry, University Medical Centre, Ljubljana, Slovenia, 3Faculty of Health Sciences, University of Ljubljana, Ljubljana, Slovenia, 4Department of Cardiovascular Surgery, University Medical Centre, Ljubljana, Slovenia.
OBJECTIVE: Acute kidney injury (AKI) represents serious complication after cardiac surgery. The assessment of AKI rests on creatinine levels, which are dependent on many parameters, causing late and less reliable AKI detection. We tested the utility of plasma neutrophil gelatinase-associated lipocalin (NGAL) and serum cystatin C (cysC) for determination of AKI after aortic valve replacement surgery.
METHODS: 65 patients were enrolled into study sample. 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 postoperative day. Statistical analyses were performed with SPSS, version 21.0, p-value <0,05 was considered significant.
RESULTS: According to Acute Kidney Injury Network classification 37% of patients developed AKI (AKI1 or AKI2). NonAKI and AKI groups were similar regarding demographics, except for higher body mass index in AKI group (27.1±0.7 vs. 29.8±0.8, p=0.017, respectively). Preoperative glomerular filtration rate was above 60 ml/min/1.73 m2 in all study participants, as were preoperative NGAL, cysC and creatinine levels similar across groups. Postoperatively, NGAL discriminated between nonAKI and most severe AKI group 2 hours after CPB (150.2±60.8 vs. 227.8±82.3; p=0.007, respectively) and later on the first postoperative day also between AKI1 and AKI2 group (79.1±40.5 vs. 116.9±60.0 (p=0.020) vs. 154.8±41.6 (p<0.0005) for nonAKI vs. AKI1 vs. AKI2, respectively). CysC levels did not differ between nonAKI and AKI2 until second postoperative day (922.3±427.5 vs. 1481.3±503.6; p=0.01, respectively). The areas under curve (AUC) of NGAL, cysC and creatinine 2 hours after the end of CPB in the ROC analysis were 0.756, 0.638, 0.518, respectively.
CONCLUSIONS: Our results demonstrate plasma NGAL effectively identifies patients who develop severe AKI after surgery. Importantly, it discriminates between nonAKI and most severe AKI group already two hours after CPB. Compared to creatinine and cysC, NGAL has remarkably higher discriminatory capacity for early detection of AKI. Although better than creatinine, cysC proved efficient in differentiating between AKI and nonAKI only later in the postoperative course.
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