NEW YORK (Reuters Health) – The risk of venous thromboembolism (VTE) after surgery is probably higher and longer-lasting than previously thought, data from the UK’s Million Women Study suggest.

In fact, the investigators report, the risk of VTE in the first 6 weeks after inpatient surgery is increased nearly 70-fold relative to not undergoing surgery. Earlier studies, by contrast, have suggested that the elevation in risk does not exceed 22-fold.

Furthermore, VTE risk is still substantially elevated from 7 to 12 weeks after surgery, lead author Dr. Sian Sweetland, from the University of Oxford, UK and colleagues state in the December 4th Online First issue of BMJ.

Excluding women with a history of VTE, cancer, and multiple surgeries left 947,454 middle aged subjects for the current analysis. They were recruited between 1996 and 2001 and followed for an average of 6.2 years per woman. During follow-up, 239,614 women underwent surgery (90,259 as inpatients), 5419 women were admitted to the hospital for VTE, and an additional 270 women had a first diagnosis of VTE at death.

In the 6 weeks following an inpatient operation, the likelihood of VTE admission was increased 69.1-fold relative to not undergoing surgery. With day surgery, a 9.6-fold increased risk was seen in the first 6 weeks. At 7 to 12 weeks postoperatively, VTE risks were still 19.6-fold higher after inpatient surgery and 5.5-fold higher after day surgery.

The pattern of risk was similar for deep vein thrombosis and pulmonary embolism, the researchers note.

Consistent with previous reports, the risk of VTE varied by surgery type. In the first 6 weeks, hip/knee replacements (RR, 220.6) and cancer surgery (RR, 91.6) had the highest risks of VTE, while gynecologic procedures had the lowest (RR, 22.7).

The new findings are “a wake-up call to all surgeons,” Dr. Alexander T. Cohen, from King’s College Hospital, London, writes in a related editorial.

“We have no studies that have examined whether (VTE prophylaxis) should be extended more than five weeks in any group of patients, but (this) study makes the case for considering such an option,” he adds.

“The study also suggests that we should be investigating the rates of VTE, the use of thromboprophylaxis, and the length of treatment in a wider range of patients, including those with and without additional risk factors for VTE.”

Reference:
BMJ 2009.