Thrombelastography Based Dosing of Enoxaparin

Hypothesis: Enoxaparin dosed to maintain a TEG® ΔR greater than 1.0 minute will decrease the incidence of DVT compared to standard dosing. Initiation of enoxaparin thromboprophylaxis will be done by the treatment team. Once enrolled, the subject will be randomized to continue receiving standard dose enoxaparin (30 mg twice daily) or variable TEG® guided enoxaparin dosing. The treatment team and the subject will be blinded regarding the arm in which the patient is enrolled. Patient characteristics: age, gender, body mass index (BMI), comorbidities, Acute Physiology and Chronic Health Evaluation II score (APACHE II), injuries, and operations will be collected. As part of standard protocol in the ICU, all patients will undergo weekly ultrasound duplex examination of the lower extremities for presence of deep venous thrombosis. A baseline TEG® will be completed on each patient when they are enrolled in the study. The blood will be drawn between four and six hours after the morning dose is administered, corresponding to maximum tissue levels of enoxaparin. TEG® assays will be run in duplicate for each patient, with and without heparinase, which negates the effects of enoxaparin in the assay. Those patients randomized to the control arm of the study will have TEG® performed at baseline and daily for one week, then twice weekly. The twice weekly TEG® assays will be done until the patient is discharged from inpatient care or enoxaparin is discontinued by the treatment team. No adjustments will be made to their enoxaparin dosing. Patients in the TEG® guided enoxaparin dosing arm will start treatment as ordered by the primary treatment team. After the second TEG®, the dose of enoxaparin will be adjusted in 10 mg increments per dose in order to reach a target ΔR between 1.0 and 1.4 minutes. If the initial ΔR is greater than 1.4 minutes, the dose of enoxaparin will be decreased by 10 mg increments until the target ΔR is achieved. Patients will have TEGs® performed daily and adjustment of dosing until the target ΔR is reached. Once the target ΔR is achieved, TEG® will be done twice weekly until the patient is discharged from inpatient care or enoxaparin is discontinued by the treatment team. All patients will be assessed daily by study personnel for bleeding complications. If bleeding complications occur, subjects will be withdrawn from the study. If interim analysis identifies a significant difference in bleeding complications between groups the study will be terminated.