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Predicting Risk for Venous Thromboembolism With Bariatric Surgery: Results From the Michigan Bariatric Surgery Collaborative

Finks, Jonathan F. MD*; English, Wayne J. MD; Carlin, Arthur M. MD; Krause, Kevin R. MD§; Share, David A. MD, MPH; Banerjee, Mousumi PhD; Birkmeyer, John D. MD*; Birkmeyer, Nancy J. PhD*for the Michigan Bariatric Surgery Collaborative and from the Center for Healthcare Outcomes and Policy

doi: 10.1097/SLA.0b013e31825659d4
Original Articles

Objective: We sought to identify risk factors for venous thromboembolism (VTE) among patients undergoing bariatric surgery in Michigan.

Background: VTE remains a major source of morbidity and mortality after bariatric surgery. It is unclear which factors should be used to identify patients at high risk for VTE.

Methods: The Michigan Bariatric Surgery Collaborative maintains a prospective clinical registry of bariatric surgery patients. For this study, we identified all patients undergoing primary bariatric surgery between June 2006 and April 2011 and determined rates of VTE. Potential risk factors for VTE were analyzed using a hierarchical logistic regression model, accounting for clustering of patients within hospitals. Significant risk factors were used to develop a risk calculator for development of VTE after bariatric surgery.

Results: Among 27,818 patients who underwent bariatric surgery during the study period, 93 patients (0.33%) experienced a VTE complication, including 51 patents with pulmonary embolism. There were 8 associated deaths. Significant risk factors included previous history of VTE (OR 4.15, CI 2.42–7.08); male gender (OR 2.08, CI 1.36–3.19); operative time more than 3 hours (OR 1.86, CI 1.07–3.24); BMI category (per 10 units) (OR 1.37, CI 1.06–1.75); age category (per 10 years) (OR 1.25, CI 1.03–1.51); and procedure type (reference adjustable gastric band): duodenal switch (OR 9.45, CI 2.50–35.97); open gastric bypass (OR 6.48, CI 2.17–19.41); laparoscopic gastric bypass (OR 3.97, CI 1.77–8.91); and sleeve gastrectomy (OR 3.50, CI 1.30–9.34). Nearly 97% of patients had a predicted VTE risk less than 1%.

Conclusions: In this population-based study, overall VTE rates were low among patients undergoing bariatric surgery. The use of an empirically based risk calculator will allow for the development of a risk-stratified approach to VTE prophylaxis.

We analyzed data from a prospective, statewide clinical registry to identify risk factors for venous thromboembolism after bariatric surgery. Among 27,818 patients, 93 (0.33%) experienced a venous thromboembolism (VTE) complication. Significant risk factors included previous history of VTE, male gender, extended operative time, BMI, age, and procedure type.

*Department of Surgery, University of Michigan, Ann Arbor, MI

Department of Surgery, Marquette General Hospital, Marquette, MI

Department of Surgery, Henry Ford Hospital, Detroit, MI

§Department of Surgery, William Beaumont Hospital, Royal Oak, MI

Department of Family Medicine, University of Michigan, Ann Arbor, MI

Department of Biostatistics, University of Michigan, Ann Arbor, MI.

Reprints: Jonathan F. Finks, MD, 2210F Taubman Center, 1500 E Medical Center Drive, Ann Arbor, MI 48109. E-mail:

Disclosure: This work was supported by a longitudinal quality improvement contract from Blue Cross and Blue Shield of Michigan and Blue Care Network, as well as funding from the Agency for Healthcare Research and Quality (1 R01 HS018050–01A1) (N.J.B.).

© 2012 Lippincott Williams & Wilkins, Inc.