OHSU

Prospective Lovenox

Thrombelastography based dosing of enoxaparin for thromboprophylaxis: a prospective randomized trial – a multi-center study

Principal Investigator: Martin Schreiber, MD

What is the Prospective Lovenox study?

We demonstrated, in a prospective non-interventional study, that thrombelastography (TEG®) can distinguish patients who will develop deep vein thrombosis (DVT) while anti-factor Xa cannot.Based on this study, we plan a prospective interventional study of patients receiving enoxaparin for DVT prevention.Patients will be randomized to receive standard or variable dosing of enoxaparin.Patients in the variable dosing group will have enoxaparin dosing adjusted to achieve a preset level of anticoagulation as demonstrated by TEG®.Outcomes compared between groups will include incidence of DVT, superficial venous thrombosis, bleeding complications, PE, and death. We hypothesize that TEG® based dosing is superior to standard dosing for the prevention of thromboembolic events without increasing the incidence of major bleeding complications. This is a multi-center study being conducted at 3 centers and is supported by the National Trauma Institute.

Why do this study?

A standard dose of enoxaparin is used in high risk patients to prevent thromboembolic complications.The prevention of DVT is critical, as it can lead to long term venous stasis disease or pulmonary embolus (PE), which causes significant morbidity and mortality.Recent data suggest that standard dosing of enoxaparin may be inadequate in the critically ill or obese patient.Anti-factor Xa levels measure the relative inhibitory activity of enoxaparin on the clotting process, but accuracy, cost, and availability remain problematic.Therefore, using anti-factor Xa levels to determine if patients are receiving correct dosing to prevent DVT may be inadequate.TEG® is a real-time assay that can evaluate each step of clot formation and breakdown.TEG® analysis has adequate sensitivity to detect enoxaparin induced changes in coagulation.

Who will be included?

Trauma or surgical patients who are prescribed Lovenox® (enoxaparin) will be eligible to participate.

What is involved?

Patients enrolled into the study will be randomized to receive the standard dose of Lovenox® ordered by their doctor or to have their dose modified based on the results of the TEG. Patients will have 5 milliliters (about 1 teaspoon) of blood drawn as often as daily or as little as once a week as long as they continue to receive Lovenox® or until discharged from the hospital, whichever comes first. We will use part of the blood sample to run the TEG, and the rest to run the most commonly used test for monitoring Lovenox® levels (anti-factor Xa).

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