According to the Centers for Disease Control and Prevention, 60,000 to 100,000 people die each year from a pulmonary embolism caused by DVT where a blood clot in a leg vein breaks free and lodges in a lung. The CDC also estimates that there are some 300,000 to 600,000 cases of DVT annually in the U.S., and that for 25% of pulmonary embolism patients, “sudden death is the first symptom.”
The American College of Chest Physicians recommended using compression devices along with administering low-molecular-weight heparin, low-dose unfractionated heparin, aspirin, or other drugs for VTE prevention depending on conditions.
A Canadian Institutes of Health Research-funded study conducted between 2007 and 2010 and published in the Annals of Internal Medicine gave 778 hip-replacement patients a daily injection of dalteparin, a low-molecular-weight heparin drug, for 10 days. Then, for the next 28 days, 386 were switched to aspirin while 400 remained on dalteparin. Five of the dalteparin and one of the aspirin patients developed a VTE. Also, “clinically significant bleeding” occurred in five patients taking dalteparin patients and two receiving aspirin.
The researchers said they chose aspirin as a comparative agent because of its effectiveness, convenience, low cost and “favorable safety record.” They concluded that “aspirin was noninferior to and as safe as dalteparin for the prevention of VTE” in hip-replacement patients who first received dalteparin. “Given its low cost and greater convenience, aspirin may be considered a reasonable alternative for extended thromboprophylaxis” after total hip replacements, they wrote.
In another study, presented earlier this year at the AAOS annual conference and slated for publication this summer, researchers compared outcomes for aspirin and warfarin in a clinical database that included reports from total joint replacement surgeries between January 2000 and June 2012. There were 26,123 patients who received warfarin for VTE prevention and 2,800 who received aspirin. Both groups took their respective drug for six weeks following surgery.
Their analysis found a pulmonary embolism rate of 1.07% among patients receiving warfarin and 0.14% for patients receiving aspirin.
“In times when medicine is aimed at quality and efficiency, the cumbersome and unpredictable nature of warfarin for post-arthroplasty VTE prevention in healthy patients should make it a drug of the past,” the researchers concluded. “Aspirin is an adequate method of chemical anticoagulation following orthopedic surgeries. In addition it is a historically well-tolerated drug, easy to administer and can simultaneously prevent the occurrence of postoperative cardiovascular accidents.”
Dr. Javad Parvizi, a co-author of the study and director of clinical research at the Philadelphia-based Rothman Institute, added that warfarin patients had more problems with bleeding and other complications.
“There has been huge issues with respect to what is the best,” said Parvizi, a professor of orthopedic surgery at Jefferson Medical College in Philadelphia. “I don't think there's any strong guidance anyone has given on what would be the best for any particular patient.”
Parvizi also noted that four to six weeks of warfarin can cost thousands of dollars, compared with a few dollars for a bottle of aspirin.
He added, however, that because this study was not based on a randomized controlled trial, “level one” evidence supporting aspirin over warfarin is still needed.
But Dr. Gregory Maynard, senior vice president of the Society for Hospital Medicine Center for Healthcare Improvement and Innovation, said that the study's “conclusion may be overstating it.”
Maynard, who also is director of the UC San Diego Center for Innovation and Improvement Science, said the findings could be affected by a variety of factors: Warfarin's therapeutic benefits take time to develop, orthopedic surgeons are also getting better at “getting patients up and going faster,” and younger patients are getting joint replacements now. Warfarin, Maynard added, is also losing favor to rivaroxaban, which is “much more problem-free.”
“I believe warfarin is going to be used less often because it's such a pain to use,” he said.
Maynard, who is writing a VTE prevention program implementation guide for the HHS Agency for Healthcare Research and Quality, said organizations will need to pick the methods that work best for their patients.
“However people decide to tackle this as an institution, they'll need to standardize what they do,” he said. “That will unclutter order sets so, instead of six options for each patient, maybe they'll have one or two.”
Maynard said the Canadian study, with its use of low-molecular-weight heparin followed by aspirin, offered a “nice middle ground,” and said this discussion will continue until the ACCP or AAOS come up with definitive best practices.
“I think there is good reason for the debate and the debate will go on for a while,” he said. “It's hard to standardize a procedure and to tell how well you're doing when you can use anything.”
Follow Andis Robeznieks on Twitter: @MHARobeznieks
