Mechanics of Hemorrhage and Hemostasis in Vascular Injury

Hemorrhagic complications from traumatic injury account for a significant portion of preventable deaths globally, with over $500 billion in annual healthcare costs in the United States alone. Despite its critical importance, the mechanisms governing hemorrhagic blood flow and shear-induced platelet aggregation (SIPA) remain poorly understood. This thesis investigates the fluid mechanics of hemorrhagic flows, focusing on the role of injury size, vascular pressure, and anatomical location in shaping primary hemostatic responses under high-shear conditions. We quantified shear rates in hemorrhagic flows and developed a large-scale in vitro hemorrhage model to replicate bleeding scenarios. Our findings revealed that SIPA can form fully hemostatic, large-scale platelet aggregates predominantly composed of platelets, with minimal fibrin involvement. To translate these insights into clinical applications, we developed a point-of-care (POC) assay to evaluate SIPA function in trauma patients. Our results show that patients with severe injuries exhibit profound SIPA dysfunction, with near-complete loss of platelet aggregation persisting up to 48 hours post-injury. The POC assay detected this dysfunction with high sensitivity, requiring only 6 mL of blood and delivering results within 10 minutes, demonstrating its potential for real-time clinical decision-making. We also explored strategies to enhance SIPA in healthy individuals, showing that supplementation with high concentrations of Von Willebrand factor (VWF) significantly accelerates platelet aggregation, reducing time to hemostasis by half and decreasing blood loss. Conversely, cryoprecipitate, tranexamic acid (TXA), and processed platelets failed to improve SIPA due to the presence of sodium citrate, which compromises platelet functionality. This research underscores SIPA's critical role in hemostasis and trauma care, offering insights into both fluid mechanics and therapeutic strategies. These findings provide a foundation for novel diagnostics and optimized treatments to improve outcomes in trauma-induced bleeding.