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Effectiveness of low-molecular-weight heparin versus unfractionated heparin to prevent pulmonary embolism following major trauma

A propensity-matched analysis

Byrne, James P. MD; Geerts, William MD; Mason, Stephanie A. MD; Gomez, David MD, PhD; Hoeft, Christopher MA; Murphy, Ryan MPH; Neal, Melanie MS; Nathens, Avery B. MD, PhD

Journal of Trauma and Acute Care Surgery: February 2017 - Volume 82 - Issue 2 - p 252–262
doi: 10.1097/TA.0000000000001321
AAST 2016 Plenary Papers

BACKGROUND Pulmonary embolism (PE) is a leading cause of delayed mortality in patients with severe injury. While low-molecular-weight heparin (LMWH) is often favored over unfractionated heparin (UH) for thromboprophylaxis, evidence is lacking to demonstrate an effect on the occurrence of PE. This study compared the effectiveness of LMWH versus UH to prevent PE in patients following major trauma.

METHODS Data for adults with severe injury who received thromboprophylaxis with LMWH or UH were derived from the American College of Surgeons Trauma Quality Improvement Program (2012–2015). Patients who died or were discharged within 5 days were excluded. Rates of PE were compared between propensity-matched LMWH and UH groups. Subgroup analyses included patients with blunt multisystem injury, penetrating truncal injury, shock, severe traumatic brain injury, and isolated orthopedic injury. A center-level analysis was performed to determine if practices with respect to choice of prophylaxis type influence hospital PE rates.

RESULTS We identified 153,474 patients at 217 trauma centers who received thromboprophylaxis with LMWH or UH. Low-molecular-weight heparin was given in 74% of patients. Pulmonary embolism occurred in 1.8%. Propensity score matching yielded a well-balanced cohort of 75,920 patients. After matching, LMWH was associated with a significantly lower rate of PE compared with UH (1.4% vs. 2.4%; odds ratio, 0.56; 95% confidence interval, 0.50–0.63). This finding was consistent across injury subgroups. Trauma centers in the highest quartile of LMWH utilization (median LMWH use, 95%) reported significantly fewer PE compared with centers in the lowest quartile (median LMWH use, 39%; 1.2% vs. 2.0%; odds ratio, 0.59; 95% confidence interval, 0.48–0.74).

CONCLUSIONS Thromboprophylaxis with LMWH (vs. UH) was associated with significantly lower risk of PE. Trauma centers favoring LMWH-based prophylaxis strategies reported lower rates of PE. Low-molecular-weight heparin should be the anticoagulant agent of choice for prevention of PE in patients with major trauma.

LEVEL OF EVIDENCE Therapeutic study, level III.

From the Sunnybrook Research Institute, Sunnybrook Health Sciences Center (J.P.B., W.G., S.A.M., A.B.N.); and Clinical Epidemiology Program, Institute of Health Policy, Management and Evaluation (J.P.B., S.A.M., A.B.N.); Division of General Surgery (J.P.B., S.A.M., D.G., A.B.N.); and Department of Surgery, Sunnybrook Health Sciences Center (W.G., A.B.N.), University of Toronto, Toronto, Ontario, Canada; and Trauma Quality Improvement Program, American College of Surgeons, Chicago, Illinois (C.H., R.M., M.N., A.B.N.).

Submitted: July 19, 2016, Revised: October 13, 2016, Accepted: October 19, 2016, Published online: November 30, 2016.

This work was supported by funds from the De Souza Chair in Trauma Research (A.B.N.).

This study was presented at the 75th annual meeting of the American Association for the Surgery of Trauma, September 14–17, 2016, in Waikaloa, Hawaii.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text, and links to the digital files are provided in the HTML text of this article on the journal’s Web site (

Address for reprints: James P. Byrne, MD, Sunnybrook Health Sciences Center, Room D-574, 2075 Bayview Ave, Toronto, Ontario, Canada M4N 3M5; email:

© 2017 Lippincott Williams & Wilkins, Inc.