Platelet count reduction during in vitro membrane oxygenation affects platelet activation, neutrophil extracellular trap formation and clot stability, but does not prevent clotting

Abstract

Introduction: Due to improved technology and increased application the mortality during extracorporeal membrane oxygenation (ECMO) is constantly declining. Nevertheless, complications including haemorrhage or thrombus formation remain frequent. Local mitigation of coagulation within an ECMO system to prevent thrombus formation on ECMO components and optimizing systemic anticoagulation is an approach to reduce clotting and bleeding complications at once. Foreign surfaces of ECMO systems, activate platelets (PLTs), which besides their major role in coagulation, can trigger the formation of neutrophil extracellular traps (NETs) contributing to robust thrombus formation. The impact of a reduced PLT count on PLT activation and NET formation is of paramount importance and worth investigating. Methods: In this study platelet poor (PLT–) and native (PLT+) heparinized human blood was circulated in two identical in vitro test circuits for ECMO devices for 6 hours. PLT reduction was achieved by a centrifugation protocol prior to the experiments. To achieve native coagulation characteristics within the test circuits, the initial heparin dose was antagonized by continuous protamine administration. Results: The PLT– group showed significantly lower platelet activation, basal NET formation and limited clot stability measured via thromboelastometry. Fluorescent and scanning electron microscope imaging showed differences in clot composition. Both groups showed equal clot formation within the circuit. Conclusions: This study demonstrated that the reduction of PLTs within an ECMO system is associated with limited PLT activation and NET formation, which reduces clot stability but is not sufficient to inhibit clot formation per se.

Thrombus formation during ECMO: Insights from a detailed histological analysis of thrombus composition

“…7,[31][32][33] Interestingly we observed a higher blood leukocyte count during ECMO supportTA B L E 3 a Kruskall-Wallis test. b χ 2 test.in35 This is in line with recent in vitro studies which have shown platelet-dependent NET formation in ECMO circuits and high shear rate-induced NET formation in a microfluidic assay 36,37. …”

“… 35 This is in line with recent in vitro studies which have shown platelet‐dependent NET formation in ECMO circuits and high shear rate‐induced NET formation in a microfluidic assay. 36 , 37 …”

Endogenous Nitric Oxide-Releasing Microgel Coating Prevents Clot Formation on Oxygenator Fibers Exposed to In Vitro Blood Flow

“…Another shortcoming is the absence of circulation; the test setting adequately generates blood flow, but no recirculation. A test circuit with constant recirculation of blood [52,53] is preferable but is not yet feasible for miniaturization, especially due to missing mini-centrifugal pumps, providing less shear forces in a test circuit in comparison to peristaltic roller pumps.…”

The Emerging Role of Neutrophils in the Pathogenesis of Thrombosis in COVID-19

“…In this study, platelet-poor (PLT-) and naive (PLT+) heparinized human blood was circulated for 6 h in two identical in vitro test circuits used for ECMO devices. The authors reported that the depletion of PLTs within the ECMO system was associated with limited PLT activation but not sufficient to inhibit clot formation [59].…”