Thrombelastography-based dosing of enoxaparin for thromboprophylaxis in trauma and surgical patients: A randomized clinical trial

Importance: Prophylactic enoxaparin is used to prevent venous thromboembolism (VTE) in surgical and trauma patients. However, VTE remains an important source of morbidity and mortality, potentially exacerbated by antithrombin III or anti-Factor Xa deficiencies and missed enoxaparin doses. Recent data suggest that a difference in reaction time (time to initial fibrin formation) greater than 1 minute between heparinase and standard thrombelastogram (TEG) is associated with a decreased risk of VTE. Objective: To evaluate the effectiveness of TEG-adjusted prophylactic enoxaparin dosing among trauma and surgical patients. Design, Setting, and Participants: This randomized clinical trial, conducted from October 2012 to May 2015, compared standard dosing (30mg twice daily) with TEG-adjusted enoxaparin dosing (35mg twice daily) for 185 surgical and trauma patients screened for VTE at 3 level I trauma centers in the United States. Main Outcomes and Measures: The incidence of VTE, bleeding complications, anti-Factor Xa deficiency, and antithrombin III deficiency. Results: Of the 185 trial participants, 89were randomized to the control group (median age, 44.0 years; 55.1% male) and 96 to the intervention group (median age, 48.5 years; 74.0% male). Patients in the intervention group received a higher median enoxaparin dose than control patients (35mg vs 30mg twice daily; P < .001). Anti-Factor Xa levels in intervention patientswere not higher than levels in control patients until day 6 (0.4 U/mL vs 0.21 U/mL; P < .001). Only 22 patients (11.9%) achieved a difference in reaction time greater than 1 minute, whichwas similar between the control and intervention groups (10.4% vs 13.5% ; P = .68). The time to enoxaparin initiationwas similar between the control and intervention groups (median [range] days, 1.0 [0.0-2.0] vs 1.0 [1.0-2.0]; P = .39), and the number of patients who missed at least 1 dosewas also similar (43 [48.3% ] vs 54 [56.3% ]; P = .30). Rates of VTE (6 [6.7% ] vs 6 [6.3% ]; P > .99)were similar, but the difference in bleeding complications (5 [5.6% ] vs 13 [13.5% ]; P = .08)was not statistically significant. Antithrombin III and anti-Factor Xa deficiencies and hypercoagulable TEG parameters, including elevated coagulation index (>3), maximum amplitude (>74 mm), and G value (>12.4 dynes/cm²), were prevalent in both groups. Identified risk factors for VTE included older age (61.0 years vs 46.0 years; P = .04), higher body mass index (calculated asweight in kilograms divided by height in meters squared; 30.6 vs 27.1; P = .03), increased Acute Physiology and Chronic Health Evaluation II score (8.5 vs 7.0; P = .03), and increased percentage of missed doses per patient (14.8% vs 2.5% ; P = .05). Conclusions and Relevance: The incidence of VTE was low and similar between groups; however, few patients achieved a difference in reaction time greater than 1 minute. Antithrombin III deficiencies and hypercoagulable TEG parameters were prevalent among patients with VTE. Low VTE incidence may be due to an early time to enoxaparin initiation and an overall healthier and less severely injured study population than previously reported.