Use of weight-based dosing of enoxaparin for venous thromboembolism prophylaxis in an extremely underweight elderly patient.

PURPOSE: The purpose of this report is to highlight a case of utilizing weight-based enoxaparin for prophylaxis of venous thromboembolism (VTE) in an elderly, extremely underweight patient. VTE represents a significant concern for hospitalized patients. There is a dearth of literature regarding utilization of low-molecular-weight heparins such as enoxaparin or unfractionated heparin in patients who are underweight.

SUMMARY: In this case, a 68-year-old female who was extremely underweight (21.8 kg) presented to the emergency department in acute respiratory distress secondary to pneumonia and a chronic obstructive pulmonary disease exacerbation. The patient had a Padua score of 5 and an IMPROVE score of 2 that signified the necessity of pharmacologic VTE prophylaxis. A clinical decision was made to utilize a weight-based enoxaparin dosing strategy for VTE prophylaxis using a pediatric dilution to deliver the dose. Enoxaparin was initiated at 0.5 mg/kg (10 mg) subcutaneously daily and monitored via anti-factor Xa peak levels to verify that the dose provided an adequate prophylactic level. Ultimately, a dose of 0.5 mg/kg resulted in an appropriate anti-factor Xa level of 0.21 units/mL, equating to suitable VTE prophylaxis.

CONCLUSION

A review of the literature revealed little evidence for optimal anticoagulation dosing for VTE prophylaxis in adult patients weighing under 40 kg. Various adjustment strategies have been utilized; however, there is no available evidence pertaining to patients at the extreme of low weight represented by the reported case or to attainment of an anti-factor Xa level within the therapeutic range in such patients. This case represents the use of a weight-based enoxaparin strategy for an extremely underweight elderly patient and the attainment of a therapeutic prophylactic anti-factor Xa level.