Treatment of suspected pulmonary embolism in a morbidly obese patient

Purpose: A case highlighting challenges with enoxaparin dosage and monitoring in obese patients is presented.

Summary: A morbidly obese 22-year-old Caucasian female (height, 168 cm; weight, 322 kg; body mass index [BMI], 114 kg/m²) who presented to the emergency department with acute-onset dyspnea and hypoxia was empirically initiated on enoxaparin for suspected pulmonary embolism at the institution's standard maximum dosage (160 mg subcutaneously every 12 hours). On hospital day 2, a peak anti-factor Xa (anti-Xa) level of 0.4 IU/mL was documented about 4 hours after the fourth enoxaparin dose. On hospital day 3, the enoxaparin dose was increased to 200 mg, a dose equivalent to 0.62 mg per kilogram of actual body weight (ABW), much lower than the guideline-recommended dose for venous thromboembolism prophylaxis (1 mg/kg). Four hours after her third 200-mg dose of enoxaparin, the patient had an anti-Xa value of 0.64 IU/mL (goal range, 0.5-1.1 IU/mL), with no evidence of bleeding or other adverse drug events. Follow-up anti-Xa testing on hospital day 4 yielded a value of 0.78 IU/mL. The case highlights the need for research to better delineate strategies for enoxaparin dosage and monitoring in the context of extreme obesity.

Conclusion: A female patient with a BMI of 114 kg/m² was safely and effectively treated using an initial twice-daily dose of enoxaparin less than the recommended 1-mg/kg dose based on ABW. Dosage adjustments were made according to anti-Xa levels, and no adverse drug reactions were noted.