Post-Injury Platelet Biology: Mechanisms and Outcomes

Overview

Trauma-induced coagulopathy is a central cause of preventable deaths from hemorrhage after injury. The contribution and impact of altered post injury platelet biology on trauma-induced coagulopathy is not well understood despite the pivotal contribution of platelets to normal coagulation and endothelial integrity. The central hypothesis for this study is that severe injury and shock drive altered platelet activation, platelet aggregation, and platelet-endothelial interactions that are associated with increased rates of transfusion, organ failure, and mortality. This study will investigate these causal pathways, mechanisms, and associated outcomes in a prospective observational trauma cohort through collection of biospecimens and detailed clinical data.

This is a prospective cohort study of trauma patients on admission to the emergency department and for the subsequent 28 days. All adult patients meeting criteria for full trauma team activation and admitted to Zuckerberg San Francisco General Hospital and Trauma center, a level-1 trauma center, are eligible for enrollment. A 20-ml sample of blood will be drawn within 10 minutes of arrival in the emergency department (ED), processed in the central laboratory, and plasma stored at -80°C. Blood samples will be collected immediately on presentation via initial placement of a 16-gauge or larger peripheral intravenous line. Plasma biomarkers of endothelial injury will be measured by enzyme-linked immunosorbent assays (von Willebrand factor, syndecan-1, and angiopoietin-2). Cellular biomarkers of platelet activation will be measured by flow cytometry (platelet-monocyte aggregates, integrin αIIbβ3, P-selectin, and platelet microparticles). Platelet aggregation will be measured by whole blood multiple electrode impedance aggregometry. The effect of post-injury platelets on endothelial integrity will be quantified by in vitro assays of platelet-induced endothelial permeability. Comprehensive demographic data and medical history will be collected from chart review, interviews of patients and family members. Detailed clinical and outcome data is collected including transfusion timing and doses, the incidence of organ failure (Denver Postinjury Multiple Organ Failure Score), acute respiratory distress syndrome (Berlin Definition), infection, symptomatic thromboembolic complications, ventilator-free days, length of intensive care unit (ICU) and hospital stay, and mortality (6 hours, 24 hours, 30 days). In hospital mortality after 30 days will be assessed for all patients. Standard coagulation measures (international normalized ratio, prothrombin time, platelet count) and other laboratory measures will be collected to account and control for other distinct but highly integrated pathways implicated in trauma-induced coagulopathy. The Trauma Registry, a large database managed under guidelines from the American Trauma society, uses chart review to retrospectively assign Injury Severity Scores (ISS) and Abbreviated Injury Scores (AIS).