Chest
Volume 128, Issue 5, November 2005, Pages 3364-3371
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Clinical Investigations: VENOUS THROMBOEMBOLISM
Identifying Orthopedic Patients at High Risk for Venous Thromboembolism Despite Thromboprophylaxis

https://doi.org/10.1378/chest.128.5.3364Get rights and content

Objective: To evaluate risk factors for venous thromboembolism (VTE) despite thromboprophylaxis in major orthopedic surgery patients at a tertiary care hospital.

Methods: Charts from consecutive patients who underwent total hip replacement (THR), total knee replacement (TKR), or hip fracture surgery (HFS) [hip pinning or hemiarthroplasty] from August 1, 1999, to April 30, 2000, at a large Canadian teaching hospital were abstracted using standardized case report forms. Data were collected on patient characteristics, surgical characteristics, and thromboprophylaxis regimen. Results of tests performed for suspected VTE were documented. Associations between characteristics of interest and objectively confirmed VTE were examined in multivariate analysis.

Results: Over the study period, 310 patients underwent major orthopedic surgery and received standard thromboprophylaxis with either dalteparin or enoxaparin (mean duration of prophylaxis, 7 days). Of these, 34% underwent THR, 30% underwent TKR, and 36% underwent HFS. Of 83 suspected cases of VTE, 44 cases (7 proximal and 37 distal deep venous thrombosis [DVT]); 14% of study population) were confirmed with objective testing. Multivariate analyses revealed that knee surgery (odds ratio [OR], 4.8; 95% confidence interval [CI], 2.3 to 10.1) and type of low molecular weight heparin (LMWH) [enoxaparin (more protective): OR, 0.39; 95% CI, 0.20 to 0.80] independently predicted VTE. No patient characteristics (including previous VTE, malignancy, hormonal therapy, postoperative complications) were associated with VTE.

Conclusion: Despite standard thromboprophylaxis, symptomatic breakthrough VTE, primarily distal DVT, developed in 14% of patients undergoing major orthopedic surgery. Factors that independently predicted VTE in our population were TKR surgery and type of LMWH. TKR patients may warrant more aggressive postoperative physiotherapy and ambulation and adjunctive prophylactic measures such as pneumatic compression. Due to the heterogeneity of different LMWH compounds, direct comparison of the effectiveness of enoxaparin with dalteparin for orthopedic prophylaxis in prospective, randomized trials seems warranted.

Section snippets

MATERIALS AND METHODS

Charts from all patients who underwent THR, TKR, or HFS (pinning or hemiarthroplasty) at our institution between August 1, 1999, and April 30, 2000, were retrieved and systematically reviewed using a standardized case report form. Patients who did not receive LMWH at the standard VTE prophylaxis dose as recommended by the thromboprophylaxis regimen for orthopedic surgery patients at our institution (see below) were excluded. Data were collected on baseline patient characteristics, type and side

RESULTS

Between August 1, 1999, and April 30, 2000, 385 patients were admitted to the Orthopedic Service for major orthopedic surgery. Of these, 75 patients were excluded because review of their charts showed that they did not receive the standard dose of LMWH for thromboprophylaxis, they did not receive any thromboprophylaxis, or they did not undergo surgery.

DISCUSSION

We studied the incidence and predictors of symptomatic breakthrough VTE in patients undergoing orthopedic surgery at a large tertiary care hospital. We found that the rate of symptomatic VTE was high, and that knee surgery and type of LWMH used for prophylaxis independently predicted symptomatic breakthrough VTE. Patient characteristics, operative factors, and traditional VTE risk factors were not independently associated with VTE in our study patients.

Our study consisted of a typical patient

ACKNOWLEDGMENTS

We thank Ms. Rosalie Johnson, RN, for administrative assistance.

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    Drs. Kahn and Shrier are recipients of Clinical Investigator Awards from the Fonds de la Recherche en Santeí du Queíbec. This study was funded in part by an unrestricted grant-in-aid from Aventis to Dr. S. Kahn. The study sponsor had no role in the design and conduct of the study, the collection, management, analysis, interpretation and reporting of study data, the writing of the manuscript or the decision to submit the manuscript for publication.

    This work was presented in part, as an abstract, at the Canadian Society of Internal Medicine Annual Meeting, Quebec City, Canada, June 2004.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).

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