Longer Surgery Linked to Higher Blood Clot Risk

The risk of developing venous thromboembolisms (VTEs) and other types of blood clots increases with longer surgeries, according to a new study published online December 3 in JAMA Surgery.

Although the link between the length of surgery and the incidence of VTE has been "widely accepted" anecdotally, the study was the first to look at a large multi-institutional sample over time, write John Y.S. Kim, MD, from the Northwestern University Feinberg School of Medicine, Chicago, Illinois, and colleagues.

The researchers analyzed data for more than 1.4 million patients undergoing general surgery at 315 US hospitals. Data came from the American College of Surgeons' National Surgical Quality Improvement Program from 2005 to 2011.

The authors looked at the rates of deep vein thrombosis, pulmonary embolism, and VTE that occurred within 30 days of surgery.

A total of 13,809 patients (0.96%) had VTE postoperatively; 0.71% had deep vein thrombosis and 0.33% experienced pulmonary embolism.

Patients with the longest surgeries had 1.27-fold (95% confidence interval, 1.21-fold to 1.34-fold; adjusted risk difference [ARD], 0.23%) the chance of developing VTE compared with the odds for an average-length surgery. Patients with the shortest surgeries had an odds ratio of only 0.86 (95% confidence interval, 0.83 - 0.88; ARD, −0.12%) compared with the average.

Surgical time was a risk factor for three of the most common surgical procedures: laparoscopic cholecystectomy (gallbladder removal), appendectomy, and gastric bypass.

More than 500,000 hospitalizations and 100,000 deaths per year are associated with VTEs. Previous studies have found that immobility from long surgeries can lead to the slowing of blood flow, an increase in blood clotting, and trauma to the blood vessels — conditions that together can lead to VTE.

Understanding the risks of lengthy surgeries could help physicians make better preoperative and postoperative decisions and better inform patients about potential hazards, the researchers write. Understanding the risks may also encourage approaches that, thanks to technological advances, shorten surgery.

The authors have disclosed no relevant financial relationships.

JAMA Surgery. Published online December 3, 2014. Full text

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