OC 69.1 - Growth of primary hemostatic clots in hemorrhagic vascular injury

Background: Hemostasis of bleeding in major vessels depends on rapid formation of a primary platelet clot. Shear-Induced Rapid Platelet Aggregation (SIPA) is a function of local shear rate. We present a mathematical analysis of occlusion time as a function of diameter and pressure for a side hole injury.

Aims: To predict the time required for hemostasis by SIPA growth following hemorrhagic injury.

Methods: SIPA aggregate growth to occlusion is a strong function of the local hemodynamics in a microfluidics system. These growth rates were applied to forecast the time to hemostasis. The rate of platelet accumulation was based on initial diameter and pressure gradient of a side hole injury. The time to hemostasis was compared to an experiment of a simulated blood vessel with a side injury coated with fibrillar collagen using heparinized porcine whole blood.

Results: The hemostatic growth rate for different size holes is shown in Figure 1A. The occlusion time by size is shown in Figure 1B. Arterial injuries < 2mm in diameter were projected to achieve hemostasis within 120 minutes, while injuries >4mm may take >4 hours to clot. At venous pressures, injuries < 4mm were anticipated to stop bleeding within 75 minutes.
In-vitro hemodynamic experiments using a 1mm side hole under 50mmHg pressure occluded in < 60 min, consistent with the model's prediction (Figure 2). Histological examination of the thrombus revealed a platelet-dominant occlusive clot.

Conclusion(s): The growth of a hemostatic clot can be estimated based on the local shear rate at the injury site. For a 4mm diameter injury, the model predicts hemostasis in 1 hour for venous injuries but over 4 hours for arterial side holes. Arterial injuries larger than 2 mm may form a partial clot but pose significant risk of exsanguination.