Thrombin generation in trauma patients.

BACKGROUND: Trauma patients are at risk of developing an acute coagulopathy of trauma (ACT) related to tissue injury, shock, and hemodilution. ACT is incompletely understood, but is similar to disseminated intravascular coagulation (DIC) and is associated with poor outcome.

STUDY DESIGN AND METHODS: Thrombin generation assays were used to evaluate plasma hemostasis in 42 trauma patients, 25 normal subjects, and 45 patients on warfarin and in laboratory-prepared factor reduced plasma. RESULTS: Prolonged prothrombin time (PT), more than 18 seconds, or an international normalized ratio of greater than 1.5 was present in 15 trauma patients indicating possible ACT. Native thrombin generation (no activator added, contact activation blocked) showed that Trauma with ACT patients had lag times 68% shorter and peak thrombin generation threefold higher than normal patients indicating the presence of circulating procoagulants capable of initiating coagulation systemically. Trauma patients had lower platelet counts and fibrinogen and Factor (F)II levels putting them at increased risk of bleeding. In laboratory-prepared isolated factor-reduced samples and in patients with vitamin K-dependent factor deficiency due to warfarin, thrombin generation decreased in direct proportion to FII levels. In contrast, in diluted plasma and in trauma patients with reduced factor levels, thrombin generation was increased and associated with slower inhibition of thrombin generation (prolonged termination time) and decreased antithrombin levels (43% of normal in Trauma with ACT).

CONCLUSIONS: Thrombin generation studies indicate that Trauma with ACT patients show dysregulated hemostasis characterized by excessive non-wound-related thrombin generation due to a combination of circulating procoagulants capable of activating coagulation systemically and reduced inhibitor levels allowing systemic thrombin generation to continue once started.

Dunbar NM, Chandler WL.
From the Department of Laboratory Medicine, University of Washington, Seattle, Washington