(HealthDay News) — Longer surgery times appear to increase a patient’s risk of deep vein thrombosis and pulmonary embolism, according to a new study published online December 3 in JAMA Surgery.

Researchers analyzed data from 1,432,855 people who had surgery under general anesthesia at 315 U.S. hospitals between 2005–2011.

Of those patients, 0.96% developed a venous thromboembolism after surgery, 0.71% developed a deep vein thrombosis, and 0.33% developed a pulmonary embolism. Patients who had the longest operations were 1.27 times more likely to develop a venous thromboembolism than those who had average-length surgeries. The risk was lowest among patients who had the shortest surgeries.

“Given the observational design of our study, it is not possible to definitively conclude that the observed relationship between surgical duration and venous thromboembolism incidence reflects a strict cause-and-effect relationship,” John Y.S. Kim, MD, of the Northwestern University Feinberg School of Medicine in Chicago, and colleagues write.

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