Optimal Dosing of Enoxaparin in Critically Ill Patients with Venous Thromboembolism

Background: Evidence suggests that goal anti-Xa levels are achieved in only 33% of critically ill patients receiving standard prophylactic enoxaparin dosing. There has been limited focus on the potential suboptimal anticoagulation effect on medical intensive care unit (MICU) patients receiving therapeutic enoxaparin dosing for venous thromboembolism (VTE). Methods: MICU patients receiving enoxaparin 1 mg/kg twice daily or 1.5 mg/kg daily for VTE treatment in a 350-bed community teaching hospital between 2013 and 2019 with at least one peak anti-Xa level measured were included. The primary outcome was the proportion who achieved therapeutic anti-Xa levels with standard dosing. Secondary outcomes included types of dose-adjustments required and the proportion requiring subsequent dose-adjustments. Descriptive statistics were presented for all outcomes. Results: Fifty-three patients were evaluated, including those receiving either twice-daily or once-daily standard therapeutic dosing. Optimal anti-Xa levels at first measurement were recorded after the initiation of enoxaparin in 26.4% (n=14) patients. Dose adjustments were required in 70.7% (n=29) of patients receiving twice-daily dosing and in 83.3% (n=10) receiving once-daily dosing (P=0.97) to appropriately increase or decrease the enoxaparin dose. By the third anti-Xa level measurement, 3 patients remained outside of the therapeutic range. Conclusions: Standard therapeutic enoxaparin dosing did not result in optimal anti-Xa levels for a majority of MICU patients regardless of dosing regimen used or patient specific factors. Future studies should identify patient factors associated with the requirement for higher or lower enoxaparin dosing.