(965) Predictors of Enoxaparin Prophylaxis Failure

Introduction: Venous thromboembolism (VTE) is a significant cause of morbidity and mortality in hospitalized patients. Several risk factors predispose hospitalized patients to the development of VTE, including prolonged immobility, obesity, age, and recent surgery. Pharmacological prophylaxis with low molecular weight heparin, such as enoxaparin, is the standard of care to reduce the risk of this complication in patients with normal renal function and otherwise appropriate clinical status. The data is unclear on how to adjust prophylactic enoxaparin dosing in the obese patient.

Methods: This was a retrospective case control study of patients who received prophylactic enoxaparin during their admission. Both intensive care and floor unit patients were included in this analysis. Cohorts were defined by whether there was a VTE diagnosis during their stay that was not present on admission or not. Patients were matched based on their admission Sequential Organ Failure Assessment score and admission date. The objective of this study was to determine risk factors for enoxaparin failure. Analyses were conducted to identify patient-specific factors independently associated with the failure of enoxaparin VTE prophylaxis, including hospital length of stay, body mass index, Charlson Comorbidity Index, and percentage of missed enoxaparin doses.

Results: A total of 442 patients were included, 221 in the VTE cohort and 221 without VTEs. Patients in the VTE cohort had a median BMI of 28 compared to a BMI of 29 in the no VTE cohort. The VTE cohort received 0.57 mg/kg/day of enoxaparin compared to 0.55 mg/kg/day (p=0.324). The median length of stay (17.5 vs 6 days; p< 0.001) and Charlson Comorbidity Index (5 vs 4; p< 0.001) was significantly higher in the VTE cohort. The analysis did not find a significant association between the percentage of missed doses and VTE incidence (p=0.895).

Conclusions: We were unable to determine a daily, weight-based dose of enoxaparin that is associated with a decreased incidence of VTE, which could have been due to the small sample size. Patient-specific factors, such as presence of extensive comorbidities and prolonged hospitalization likely led to an increased risk of enoxaparin failure.