Neutrophil extracellular traps (NETs) have recently emerged as a potential link
between inflammation, immunity, and thrombosis, as well as other coagulation
disorders which present a major challenge in the context of extracorporeal
membrane oxygenation (ECMO). By examining blood from ECMO patients for
NETs and their precursors and correlating them with clinical and laboratory
biomarkers of coagulation and inflammation, this study aims to evaluate the
association between the presence of NETs in the bloodstream of ECMO patients
and the development of potentially severe coagulation disorders during ECMO
therapy. Therefore, blood samples were collected from healthy volunteers (n=13)
and patients receiving veno-venous (VV) ECMO therapy (n=10). To identify NETs
and their precursors, DNA and myeloperoxidase as well as granulocyte marker
CD66b were visualized simultaneously by immunofluorescence staining in serial
blood smears. Differentiation of DNA-containing objects and identification of
NETs and their precursors was performed semiautomatically by a specific
algorithm using the shape and size of DNA staining and the intensity of MPO
and CD66b signal. Neutrophil extracellular traps and their precursors could be
detected in blood smears from patients requiring VV ECMO. Compared to
volunteers, ECMO patients presented significantly higher rates of NETs and
NET precursors as well as an increased proportion of neutrophil granulocytes
in all detected nucleated cells. A high NET rate prior to the initiation of ECMO
therapy was associated with both increased IL-6 and TNF-a levels as an
expression of a high cytokine burden. These patients with increased NET
release also presented an earlier and significantly more pronounced decrease in platelet counts and ATIII activity following initiation of therapy compared with
patients with less elevated NETs. These findings provide further indications for
the development of immune-mediated acquired thrombocytopenia in
ECMO patients.