Prophylactic Enoxaparin in Critically Ill Trauma Patients: Evaluation of the Initial Dose

Background: Trauma patients are at increased risk of developing venous thromboembolism given alterations in the coagulation cascade. Chemoprophylaxis with standard dosing of enoxaparin 30 mg subcutaneously twice daily has evolved to incorporate the use of anti-factor Xa (AFXa) trough level monitoring given concerns for decreased enoxaparin bioavailability in this patient population. Current available evidence suggests low rates of goal AFXa trough level achievement with standard enoxaparin dosing. Our study aims to identify the incidence of critically ill trauma patients that did not achieve goal AFXa trough levels and attempts to identify predictors that may influence the lack of achievement of goal levels. Methods: This was a retrospective, cohort analysis performed at a single academic medical center. Adult patients 18 years or older admitted to the surgical intensive care unit secondary to trauma who were initiated on standard prophylactic enoxaparin and had at least 1 AFXa trough level representative of steady state were included. Patient demographics and clinical data were collected, and descriptive statistics were utilized. All statistical tests were 2-tailed and a P < .05 was considered significant. Variables with a P < .10 on univariable analysis were included in a multivariable logistic regression analysis. Results: A majority of our patient population did not achieve goal AFXa trough levels while receiving standard doses of prophylactic enoxaparin (82.4% [108/131]). Sub-target AFXa levels were associated with higher creatinine clearance values. Positive predictors of obtaining target AFXa levels included automobile versus pedestrian mechanism of injury and requiring an enoxaparin dose escalation to at least 40 mg twice daily. Conclusions: Our study found low rates of achievement of goal AFXa trough levels in critically ill trauma patients receiving standard prophylactic enoxaparin dosing. Certain variables were identified as negative and positive predictors for achievement of goal AFXa trough levels, although the biologic plausibility of these predictors is questionable and requires further investigation.