Surgeons commonly provide enoxaparin prophylaxis to high-risk patients to decrease venous thromboembolism risk. The authors’ prior work demonstrated that most patients receive inadequate venous thromboembolism prophylaxis, based on anti–factor Xa level, when enoxaparin 40 mg/day is provided and that peak anti–factor Xa level correlates with weight. This study models a weight-based strategy for daily enoxaparin prophylaxis and its impact on anti–factor Xa levels.
The authors enrolled plastic surgery patients who received enoxaparin 40 mg/day and had anti–factor Xa levels drawn. The enoxaparin dose of 40 mg was converted to a milligram-per-kilogram dose for each patient. Stratified analysis examined the milligram-per-kilogram dose that produced low, in-range, and high anti–factor Xa levels to identify the appropriate milligram-per-kilogram dose to optimize venous thromboembolism prevention and bleeding events.
Among 94 patients, weight-based dosing ranged from 0.28 to 0.94 mg/kg once daily. For peak and trough anti–factor Xa levels, there was nearly complete overlap for milligram-per-kilogram dosing that produced low versus in-range anti–factor Xa levels. For peak anti–factor Xa, there was nearly complete overlap for milligram-per-kilogram dosing that produced in-range versus high anti–factor Xa levels. Mean milligram-per-kilogram dose was not significantly different between patients who did or did not have postoperative venous thromboembolism (0.41 mg/kg versus 0.52 mg/kg; p = 0.085) or clinically relevant bleeding (0.48 mg/kg versus 0.51 mg/kg; p = 0.73).
Alterations in enoxaparin dose magnitude based on patient weight cannot allow a high proportion of patients to achieve appropriate anti–factor Xa levels when once-daily enoxaparin prophylaxis is provided. Future research should examine the impact of increased enoxaparin dose frequency on anti–factor Xa levels, venous thromboembolism events, and bleeding.
Salt Lake City, Utah
From the Divisions of Plastic Surgery, Health Services Research, and Pharmacy, University of Utah.
Received for publication December 20, 2016; accepted March 3, 2017.
This trial is registered under the name “Enoxaparin Metabolism in Reconstructive Surgery Patients,” ClinicalTrials.gov identification number NCT02411292 (https://clinicaltrials.gov/ct2/show/NCT02411292).
Disclosure:None of the authors has a financial interest in any of the products, devices, or drugs mentioned in this article.
This work was supported by THE PLASTIC SURGERY FOUNDATION.
Christopher J. Pannucci, M.D., M.S., Division of Plastic Surgery, Division of Health Services Research, University of Utah, 30 North 1900 East, 3B400, Salt Lake City, Utah 84132, email@example.com