Adjusted-Dose Enoxaparin for VTE Prevention in the Morbidly Obese

Background: Venous thromboembolism (VTE) is a major health problem and common cause of morbidity and mortality in hospitalized patients. While trials in both surgical and medically ill patients have demonstrated efficacy and safety of enoxaparin for VTE prophylaxis (VTEP), they failed to adequately represent morbidly obese (body mass index > 40 kg/m²) patients. Objective: To assess the impact of a weight-adjusted enoxaparin dosing algorithm on anti-factor Xa levels, thrombosis, and bleeding in morbidly obese patients. Methods: A retrospective chart review was conducted, which included morbidly obese patients receiving VTEP with adjusted-dose enoxaparin. Patients received enoxaparin 0.5 mg/kg subcutaneously once or twice daily based on VTE risk. An anti-factor Xa level was drawn 3 to 5 hours after 2 or more consecutive doses. The primary outcome was the percentage of patients achieving target anti-factor Xa levels, defined as 0.2 to 0.6 IU/mL. Secondary outcomes included the incidence of symptomatic VTE and major bleeding. Results: Of the 182 charts reviewed, 141 anti-factor Xa levels from 130 patients met inclusion criteria. The study population was 44% male, and the median body mass index was 45.6 kg/m². A total of 120 anti-factor Xa levels (85.1%) were within the target prophylactic range. Sixteen anti-factor Xa levels (11.3%) were below target range, and 5 (3.4%) were above range. The only significant difference among the 3 groups was baseline renal function (P = .035). There were 2 thromboembolic events and 1 major bleed in the study population. Conclusion: A weight-based VTEP dosing strategy for morbidly obese patients is effective without an apparent increase in adverse events.