U-M study: 1 in 84 high-risk patients suffer VTE after outpatient surgery

University of Michigan Health System study reveals need for better screening, prevention of venous thromboembolism as numbers of outpatient surgeries grow

A University of Michigan Health System study examined who's having outpatient surgery in the U.S. today, and showed 1 in 84 highest-risk patients suffers a dangerous blood clot after surgery.

Hospitalized patients are often warned of the possibility of venous thromboembolism, which include blood clots that can form in the veins and travel to the lungs.

However these warnings have not necessarily been extended to the outpatient surgery population, says U-M surgeon and lead study author Christopher J. Pannucci, M.D.

With more than 60 percent of procedures now being done in the outpatient setting, the U-M study revealed a need for better patient screening of the large and growing group of patients having outpatient surgery.

"Once a setting for those having simple procedures, outpatient surgery now includes a greater variety of procedures from plastic surgery to cancer operations and orthopedic surgery, and not all patients are young, healthy individuals," says Pannucci, of the U-M Section of Plastic Surgery.

Previous research shows that despite an increase in the presence of VTE risk factors among patients, such as advanced age and obesity, fewer than 50 percent of outpatient centers have VTE prevention guidelines, and even fewer adhere to them.

The U-M study published in Annals of Surgery provides a view of what drives an increased risk for VTE in the changing outpatient surgery environment.

Researchers evaluated more than 200,000 outpatient surgeries at centers across the country included in the American College of Surgeons' National Surgical Quality Improvement Program Participant Use File.

Vein surgery and arthroscopic surgery are important drivers of VTE risk, which is well-known, but the U-M analysis showed that a majority of patients had multiple factors that could put them at risk for blood clots. Age, surgery length, current pregnancy, active cancer and type of surgical procedure were all indicators of VTE risk.

With the information, the researchers created and validated a risk-stratification tool that can be used to predict a patient's risk for VTE.

The tool identified a 20-fold variation in VTE risk from 0.04 percent to 1.12 percent among the outpatient surgery population.

"These data are in stark contrast to provider and patient expectations that outpatient surgery is a low-risk event," Pannucci says. "It also underscores the importance of evaluating a patient's individual risk factors as opposed to procedure-type alone."

The risk model identified by the U-M may improve the informed consent process for outpatient surgery patients by providing clear, data-driven information to patients about their risk for developing VTE, authors say.

Prevention of VTE is considered a major patient safety issue and indicator of quality care by the U.S. Surgeon General.

As a result, hospitals, including the University of Michigan Health System, have developed robust VTE prevention guidelines for patients.