Enoxaparin in the Treatment of Pulmonary Embolism in a Morbidly Obese Patient – Case Report

Introduction

According to estimates, the prevalence of obesity worldwide has tripled since 1980. In 2014, according to the World Health Organization (WHO), increased weight, assessed based on BMI, was present in 39% of the population over 18 years old. Obesity is a significant risk factor for the development of thromboembolic disease, besides being a cause of various other mechanical and metabolic complications. Furthermore, it is often associated with other risk factors like reduced mobility, chronic diseases, smoking, and certain medications.

Treating thrombotic complications in this growing population presents a real challenge. The high weight of patients may require increased dosing of anticoagulants, whose effectiveness and safety are often not well explored, as morbidly obese patients are not included in usual clinical studies. The authors of the following illustrative case report aimed to describe the challenges of treating suspected pulmonary embolism in a morbidly obese patient.

Case Description

A 22-year-old woman was admitted to the emergency department due to sudden onset of dyspnea and hypoxia. She measured 168 cm in height and weighed 322 kilograms, resulting in a calculated BMI of 114 kg/m², which is far above the threshold for class 3 obesity as per WHO.

Her medical history included starting hormonal contraception 3 months prior and being immobilized due to her high weight. Her personal history noted post-traumatic stress disorder, anxiety and depressive disorders, morbid obesity, obstructive sleep apnea, and mild asthma. Initial laboratory tests showed borderline leukocytosis, elevated BNP levels (1620 pg/ml), slightly elevated troponins, and increased D-dimer levels (719 ng/ml). Other laboratory parameters were without serious deviations.

Blood gas analysis indicated respiratory insufficiency, requiring the patient to receive 15 l/min of oxygen to maintain saturation > 90%. No ischemic changes were observed on the ECG, and both transthoracic echocardiography and lower limb ultrasonography were normal, notwithstanding the difficulty due to the patient's body habitus.

In the differential diagnosis, pulmonary embolism, asthma exacerbation, or pneumonia were considered. Unfortunately, due to the patient's body habitus, a CT scan was not possible, and a chest x-ray showed no infiltrates or tissue consolidation. Thus, pulmonary embolism was empirically diagnosed.

Due to her weight, therapy with enoxaparin in the maximum dose (as per local standards) of 160 mg every 12 hours was initiated. Concurrently, owing to the possible asthma exacerbation, the patient received 60 mg of prednisone daily for 5 days. Peak anti-Xa activity was measured 4 hours after the fourth dose of enoxaparin, with a result of 0.4 IU/ml, outside the therapeutic range of 0.5–1.1 IU/ml.

On the third day of hospitalization, the enoxaparin dose was increased to 200 mg every 12 hours (an equivalent dose of 0.62 mg/kg based on the patient's actual weight, much lower than the recommended maximum dose of 1 mg/kg). Peak anti-Xa was re-measured after 4 doses of enoxaparin, yielding a result of 0.64 IU/ml, within the therapeutic range. The measurement was repeated on the fourth day of hospitalization, showing a result of 0.78 IU/ml. No bleeding or other adverse events associated with the therapy were observed during the hospital stay. The patient's condition significantly improved, and she no longer required oxygen therapy by the third day of hospitalization. She was discharged to home care with the hormonal contraception discontinued and a plan for gradual transition to warfarin anticoagulant therapy.

Conclusion

This case report of a 22-year-old morbidly obese patient describes clinical experience with anticoagulant therapy of pulmonary embolism using low molecular weight heparin (enoxaparin) with a positive clinical response, absence of adverse events, and the necessity for extremely high dosing to achieve effective anti-Xa levels. However, dosing based on actual weight was still far below the recommended maximum dose of 1 mg/kg. The case report also highlights the diagnostic challenges of thromboembolic disease due to morbid obesity, which limits the feasibility and yield of various examinations.

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Source: Heitlage V., Borgstadt M. B., Carlson L. Treatment of suspected pulmonary embolism in a morbidly obese patient. Am J Health Syst Pharm 2017; 74 (13): 977–980, doi: 10.2146/ajhp160111.