In-vitro Clot Formation and Failure

Thesis (Master's)--University of Washington, 2016-08

A primary cause of bleeding and mortality after traumatic injury is failure of hemostatic clot formation at wound sites. After trauma, approximately 25-30% of severe injured patients display trauma induced coagulopathy (TIC) which is a multifactorial condition that causes poor clot formation and performance. A decreased level of viscoelastic clot stiffness or strength and rapid clot breakdown by enzymatic degradation are hallmarks of this condition. Clots formed under these conditions are unable to withstand hemodynamic forces of flowing blood, and therefore are likely to repeatedly rupture, leading to progressive bleeding and worsening coagulopathy. Current research examines clot formation to understand TIC and to guide treatment. However, the most useful and clinically-relevant aspect of clot formation, for TIC, is clot durability (i.e. its resistance to breakdown) instead of the initiating events related to clot formation. Decreased clot viscoelastic firmness is among the first changes taking place during TIC, which can be detected using current viscoelastic monitors including thrombelastograpy (TEG) and rotational thromboelastometry (ROTEM). However, these devices (TEG/ROTEM) are not ideal modalities for assessing clot mechanical properties in trauma conditions due to the amount of time taken to obtain results, poor sensitivity, repeatability, and lack of standardization. Therefore, in this thesis, I examine clot durability and failure characteristics using a novel method to better understand TIC and develop new clinically-relevant point-of-care diagnostic. I developed a system that forms a clot in a small tube and then applies increasing pressure until the clot fails. I show that that clot failure is strongly associated with intrinsic mechanical properties of the clot. I show the effect of fibrinogen, factor XIIIa, platelet count on the in-vitro failure pressure of the clot. The clot failure system shows strong correlation with the maximum clot firmness obtained from ROTEM, suggesting that it could be used to diagnose TIC and inform the clinicians on the pressure at which clots will fail in patients, thus guiding patient care in trauma situations.