Nurses caring for postoperative patients, particularly middle-aged women undergoing orthopedic procedures, have new evidence to support a medical-team discussion on the merits of longer prophylaxis for venous thromboembolic events in certain populations. A recent report of a large trial conducted in the United Kingdom (the Million Women Study) reveals that the optimal duration of postoperative venous thromboembolism prophylaxis in middle-aged women may be 12 weeks, depending on the type of surgery. The risk of thromboembolic events during the first six weeks after surgery was 200 times greater in women undergoing knee or hip replacement than in women who didn't have surgery-and 90 times greater in women undergoing hip fracture surgery. Surgery for cancer also carried a much higher risk. And, in what is possibly the most significant finding, the risk remained high from postoperative weeks 7 to 12. Current guidelines from the American College of Chest Physicians call for pharmacologic prophylaxis for a maximum of 35 days after various orthopedic procedures (hip fracture surgery and total hip replacement) and shorter durations after lower-risk operations.

Researchers followed 947,454 women (mean age, 56 years) without a history of hospitalization for venous thromboembolism for a mean of 6.2 years. Venous thromboembolic events and deaths from such events were ascertained from hospital admission and death records. During follow-up, around 25% of the women underwent surgery, and more than a third of first thromboembolic events recorded occurred in that group of women. Inpatient surgery carried a much higher risk of venous thromboembolism than day surgery did, although the risk in day-surgery patients, in comparison with women who didn't have surgery, was still 10 times higher in the first week after day surgery and six times higher in weeks 7 to 12.

"These findings suggest that the risk of venous thromboembolism after surgery is greater and lasts for longer than previously thought," the authors wrote. "Overall, we found increased relative risks of venous thromboembolism during the [first] 17 postoperative weeks that were much larger than those reported previously."

Wayne Kuznar