Louise Schilder, S Azam Nurmohamed, Pieter M ter Wee, Nanne J Paauw, Armand RJ Girbes, Albertus Beishuizen, Robert HJ Beelen, AB Johan Groeneveld Critical Care 2014, 18:R78 (22 April 2014)

Introduction: Neutrophil gelatinase-associated lipocalin (NGAL) is a biomarker of acute kidney injury (AKI) and levels reflect severity of disease in critically ill patients. However, continuous venovenous hemofiltration (CVVH) may affect plasma levels by clearance or release of NGAL by activated neutrophils in the filter, dependent on the anticoagulation regimen applied. We therefore studied handling of NGAL by CVVH in patients with AKI.

Methods: Immediately before initiation of CVVH, pre-filter blood was drawn. After 10, 60, 180 and 720 minutes of CVVH, samples were collected from pre- and post-filter (in- and out-let) blood and ultrafiltrate. CVVH with the following anticoagulation regimens were studied: no anticoagulation in case of a high bleeding tendency (n = 13), unfractionated heparin (n = 8) or trisodium citrate (n = 21). NGAL levels were determined by enzyme-linked immunosorbent assay (ELISA).

Results: Concentrations of NGAL at inlet and outlet were similar and concentrations did not change over time in any of the anticoagulation groups, thus there was no net removal or production of NGAL. Concentrations of NGAL at inlet correlated with disease severity at initiation of CVVH and at the end of a CVVH run. Concentrations of NGAL in the ultrafiltrate were lower with citrate-based CVVH (P = 0.03) and decreased over time, irrespective of anticoagulation administered (P < 0.001). The sieving coefficient and clearance of NGAL were low and decreased over time (P < 0.001).

Conclusions: The plasma level and biomarker value of NGAL in critically ill patients with AKI are not affected by CVVH, since clearance by the filter was low. Furthermore, there is no evidence for intrafilter release of NGAL by neutrophils, irrespective of the anticoagulation method applied.

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