Guideline-Compliant Enoxaparin Doses Are Insufficient in the Majority of Plastic Surgery Patients: An Examination of Enoxaparin Metabolism
Christopher J. Pannucci, MD MS1, Brad Rockwell, MD1, Kory Fleming, MPH1, Maureen Ghanem, PharmD1, Arash Momeni, MD2, Jay Agarwal, MD1.
1University of Utah, Salt Lake City, UT, USA, 2University of Pennsylvania, Philadelphia, PA, USA.
Purpose: Despite guideline-compliant enoxaparin prophylaxis, one in 25 highest risk patients has a VTE event. We examined the pharmacokinetics of standard enoxaparin doses in plastic surgery patients with an emphasis on total body surface area surgically injured (TBSI) as a predictor of enoxaparin metabolism.
Methods: The Plastic Surgery Foundation funded this ongoing prospective interventional study, which recruited adult plastic surgery patients receiving post-operative enoxaparin (40mg once daily). Steady-state peak and trough anti-Factor Xa (aFXa) levels, which marks enoxaparin effectiveness and safety, were drawn. Patients with out-of-range aFXa levels had real-time dose adjustment based on a written protocol.
Results: 53 patients have been recruited, and 39.6% had in-range peak aFXa levels. 61.5% of patients had nondetectable aFXa 12 hour trough levels. Patients with increased TBSI were less likely to have in-range aFXa peak and trough levels (Figures 1/2). Amongst out-of-range patients who received dose adjustment, 58.3% achieved in-range peak aFXa levels.
Conclusions: Enoxaparin 40mg once daily provides adequate prophylaxis in less than 40% of patients. 61.5% of patients had nondetectable aFXa levels at 12 hours. Thus, the majority of patients are protected for less than 12 hours per day. Individualized, TBSI-based enoxaparin dosing regimens and real-time aFXa monitoring deserve further study.
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