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Introduction
Acute kidney injury (AKI) is a common postoperative complication after cardiac surgery with a high impact on short- and long term mortality and morbidity [1-5]. According to current guideline recommendations, it is defined by a rise in serum creatinine (SCr) and/or decline in urine volume [6], however, these subsequent effects emerge with delay after the damage itself occurred [7]. Early detection of tubular stress/damage with regard to prediction of AKI may potentially help to prevent overt AKI by adjusting medical therapy. Other biomarkers of AKI (e.g. Cystatin C, NGAL) are of limited relevance for AKI prediction as they do not provide any gain of time over SCr [4-6, 8-11].
The Nephrocheck® system combines two tubular stress biomarkers – insulin-like growth factor-binding protein 7 (IGFBP7) and tissue inhibitor of metalloproteinases-2 (TIMP-2) – for an early detection of tubular damage. Recent publications indicate that this method can detect AKI endangered patients in a very early state [7, 12-15]. Yet, it is unknown at which time-point [TIMP-2*IGFBP7] (Nephrocheck®) measurement should be performed to predict AKI in patients undergoing cardiac surgery [16-18].
The present study aims to investigate the predictive value of [TIMP-2*IGFBP7] measurements at various time points with the incidence of AKI within 48 hours after elective cardiac surgery. Furthermore, we investigated whether the predictive ability of [TIMP-2*IGFBP7] was increased if it was combined with routinely available preoperative and intraoperative factors.
Materials and Methods
The current study was part of a prospective cohort study to analyze the association of the Catechol-O-Methytransferase genotype with the incidence of AKI after cardiac surgery [19]. Adult patients were eligible if they were undergoing elective cardiac surgery (coronary artery bypass graft [CABG] with or without mammary artery bypass, valve surgery [reconstruction, replacement] with or without removal of the atrial auricle, combined CABG and valve surgery, or surgery of the thoracic aorta) involving cardiopulmonary bypass (CPB) at the Dept. of Cardiovascular Surgery, University Hospital Würzburg. Patients with advanced stages of chronic kidney disease (CKD, eGFR<60 ml/min/1.73m2) were excluded as well as individuals with signs of active infection (clinical assessment), on medication with COMT inhibitors, MAO inhibitors or with immunosuppressive therapy and women during pregnancy and lactation. The study protocol and data handling was approved by the Ethics Committee of the Medical...