Venous Thromboembolism and Bleeding Risk in a Population with Obesity Hospitalized for Surgery and Receiving Enoxaparin for Thromboprophylaxis

Introduction: Obese patients hospitalized for surgery are at high risk of venous thromboembolism (VTE). The optimal dose and duration of thromboprophylaxis with low molecular weight heparin for these patients are uncertain. Aims To assess the time-course, rates and risk factors for VTE and major bleeding (MB) in a population of surgical patients with obesity receiving pharmacological thromboprophylaxis with enoxaparin. Methods Patients with body mass index (BMI) > 30 kg/m ² hospitalized with surgeries between 2010 and 2019 who received thromboprophylaxis with enoxaparin were selected from the US Optum database. Exclusion criteria were VTE, MB, or surgery in previous 90-days, and ongoing anticoagulant treatment or dual antiplatelet therapy. VTE and MB event rates over a 90-day follow-up post enoxaparin initiation were estimated via the Kaplan-Meier (KM) method. Risk factors associated with outcome events were identified via Cox proportional hazard models. Results A total of 30,492 patients met selection criteria (median age 55, IQR 48–66), 12,058 patients received the standard dose, with 18,300 receiving higher doses. KM event rates at 90-days for VTE and MB were 2.5% and 1.2%, respectively. The highest VTE rates were observed in patients hospitalized for thoracic surgery (4.9%). History of VTE was the strongest predictor of post-surgery VTE (HR 5.58, 95% CI 4.69–6.63) while history of MB was the strongest predictor of post-surgery bleeding (HR 2.71, 95% CI 1.34–5.48). Conclusions The rates of VTE are non-negligible in surgical patients with obesity receiving thromboprophylaxis with enoxaparin. Individual risk stratification is warranted to identify optimal doses/duration of pharmacologic thromboprophylaxis.