Effect of blood flow on platelets, leukocytes, and extracellular vesicles in thrombosis of simulated neonatal extracorporeal circulation

Abstract

Background: Extracorporeal membrane oxygenation (ECMO) has frequent and sometimes lethal thrombotic complications. The role that activated platelets, leukocytes, and small (0.3-micron to 1-micron) extracellular vesicles (EVs) play in ECMO thrombosis is not well understood.Objectives: To test the effect of blood flow rate on the generation of activated platelets, leukocytes, and EVs in a simulated neonatal ECMO circuit using heparinized human whole blood. Methods: Simulated neonatal roller pump circuits circulated whole blood at low, nominal, and high flow rates (0.3, 0.5, and 0.7 L/min) for 6 h. Coagulopathy was defined by thromboelastography (TEG), STA ® -procoagulant phospholipid clot time (STA ®-Procoag-PPL), and calibrated automated thrombogram. High-resolution flow cytometry measured the cellular expression of prothrombotic phospholipids and proteins on platelets, leukocytes, and EV. Results: Despite heparinization, occlusive thrombosis halted flow in two of five circuits at 0.3 L/min and three of five circuits at 0.7 L/min. None of the five circuits at 0.5 L/min exhibited occlusive thrombosis. Phosphatidylserine (PS)-positive platelets and EVs increased at all flow rates more than blood under static conditions (P < .0002). Tissue factor (TF)-positive leukocytes and EVs increased only in low-flow and high-flow circuits (P < .0001). Tissue factor pathway inhibitor (TFPI), at 50 times more than the concentration in healthy adults, failed to suppress thrombin initiation in low-flow and high-flow circuits.Conclusions: This in vitro study informs ECMO specialists to avoid low and high blood flow that increases TF expression on leukocytes and EVs, which likely initiate clot formation. Interventions to decrease TF generated by ECMO may be an effective approach to decrease thrombosis.

Current Understanding of Leukocyte Phenotypic and Functional Modulation During Extracorporeal Membrane Oxygenation: A Narrative Review

“…In response to the continuous exposure to non-physiological conditions (e.g. flow rates and associated shear stress) and significant release of inflammatory mediators during ECMO ( 16 , 18 , 34 , 35 , 37 , 39 , 65 – 67 ), cells of the endothelial lining are likely to convert into an activated state ( 68 , 69 ). This can subsequently elevate leukocyte adhesion [from phenotypic modulation ( 13 , 17 , 18 , 34 – 36 )] onto either the artificial surface of the ECMO circuit ( 23 , 24 , 70 ) or the endothelium itself ( 68 , 69 ), possibly acting as a consistent regulator of cell attachment in vivo .…”

“…Two recently published ex vivo studies reported ECMO flow rates and the mediated non-physiological shear stress as potential influencing factors ( 37 , 39 ). During continuous ECMO blood flow, wall shear stress within the rigid ECMO circuit increases to non-physiological levels as blood flow elevates.…”

“…In addition, for each oxygenator design and size there is likely an optimal flow for different cellular components that differentially minimizes non-physiological shear stress and damage, as seen in Meyer et al. study ( 39 ). Further animal and clinical research is required to validate the ex vivo effect of ECMO flow rate specific to leukocyte modulation.…”

<p>Extracellular Vesicle-Related Thrombosis in Viral Infection</p>

“…[162][163][164][165] However, a similar role of exosomes and MVs is assumed in COVID-19 as other virus infectious diseases. [166][167][168][169][170] In particular, concerning thrombosis, there is no doubt that COVID-19 causes more symptoms in comparison with the past virus infectious disease. 171 Accumulation of important reports of EVs in conjunction with COVID-19 is expected in the future.…”

Contact activation and acquired von Willebrand syndrome during neonatal extracorporeal circulation

“…With great interest, we read the work of Meyer et al, who used a mock neonatal extracorporeal membrane oxygenation (ECMO) circuit to investigate the impact of varying flow rates on platelet activation, leukocytes, extracellular vesicles, and thrombin generation in vitro 1 . We appreciate the authors’ efforts toward refining treatment to prevent device‐related thrombosis as a major cause of morbidity and mortality in this particular group of patients.…”