Aspirin is an effective – and lower-cost – alternative to the blood-thinner warfarin when it comes to preventing blood clots after joint replacement surgery. And for the majority of patients, aspirin is the safer of the two drugs, according to a study presented at the recent American Association of Hip and Knee Surgeons annual meeting.

“There has been a huge shift toward the use of aspirin and away from using expensive drugs that [may] result in worse problems than the problem we are trying to prevent,” explains senior author Javad Parvizi, MD, director of clinical research at the Rothman Institute at Thomas Jefferson University Hospital in Philadelphia.

Following a total joint replacement, patients are often given warfarin (Coumadin) to prevent a serious blood clot called deep vein thrombosis (DVT). DVTs can break off, travel to the lungs and cause a deadly blockage there, called pulmonary embolism (PE). But Dr. Parvizi says it’s become increasingly clear that the medication also leads to increased bleeding, infections and hospital readmissions.

His recent study analyzed more than a decade of records on 28,923 patients who had joint replacement surgery at Thomas Jefferson University Hospital between 2000 and 2012. To reduce the risk of clotting, patients received either 325 milligrams (mg) of aspirin twice daily or an appropriate dose of warfarin for six weeks after surgery.

After adjusting for age, gender, health issues and type of surgery (knee or hip replacement), the researchers found that patients taking aspirin had a PE rate of 0.11 percent, compared to a PE rate of 0.67 percent in the warfarin group. In other words, patients getting warfarin were more than six times more likely to experience a PE (even though the absolute risk was still small in both cases).

The rate of DVT was also significantly lower among patients getting aspirin (0.11 percent) compared to those getting warfarin (0.91 percent). The aspirin group also had fewer wound-related problems and shorter hospital stays, but the infection rates and 90-day mortality rates were not significantly different between the two groups.

“Aspirin doesn’t result in hematoma formation or bleeding, and patients are much less likely to need re-admission or develop infection,” explains Dr. Parvizi, who says these side effects are not usually associated with aspirin but are associated with other anticlotting (also called anticoagulation) drugs. “These are very important events which we are trying to avoid and, in this day and age with limited resources in health care, it’s extremely important we use agents that are effective and less risky,” he adds.
 

He says aspirin is also cheaper and easier for patients to take. “Aspirin is pennies compared to the higher cost for anticoagulation medicines. Patients can take it on a daily basis with no need for monitoring,” Dr. Parvizi explains.

Dr. Parvizi says the key with aspirin is that it be used as part of a multi-faceted approach to prevent blood clots that includes the use of lower extremity compression devices during hospitalization. Similar to a blood pressure cuff, these compression devices, when inflated, gently squeeze the leg and increase blood flow from the lower extremity back to the heart.

Another important component, Dr. Parvizi says, is regional anesthesia or spinal anesthesia during the procedure, because it’s been shown to reduce the accumulation of blood in the leg veins and is associated with a lower incidence of DVT. Dr. Parvizi says intravenous heparin, a blood thinner, should also be used during surgery to reduce the risk of clots, and patients should be promptly “ambulated” –  that is, gotten out of bed within as little as two hours of the procedure.

The Rothman Institute at Jefferson has begun replacing warfarin with aspirin in the vast majority of joint replacement cases according to Dr. Parvizi and he expects other institutions will do the same since, he points out, new guidelines from the American College of Chest Physicians say aspirin can be used as an anticoagulation option to prevent against PEs in some joint-replacement patients. The American Academy of Orthopaedic Surgeons now considers this accepted practice as well, in certain low-risk patients..

“Patients who have had previous VTE [venous thromboembolism], are morbidly obese and are sedentary are at higher risk of subsequent VTE and may require a more aggressive form of prophylaxis [prevention]. Anyone else can be prophylaxed with aspirin,” Dr. Parvizi explains.

Geoffrey Westrich, MD, associate professor of clinical orthopedic surgery at Weill Cornell Medical College and co-director of joint replacement research at Hospital for Special Surgery (HSS) in New York, says he agrees aspirin is effective for low-risk patients – and HSS uses it in those cases. But he has questions about the methods of this study, including the vastly uneven number of participants in the two groups, because more than 26,000 received warfarin, compared to only 2,800 participants who got aspirin. He also says it’s tough to get an accurate assessment of pulmonary embolism rates from a retrospective chart review.

“The reality is, [after surgery] in our hospital, many patients [with] complications go to a local ER or another hospital, so it’s very hard to keep track of every single pulmonary embolism,” Dr. Westrich explains.

He also stresses that if patients are considered at high risk for complications, he still believes warfarin is better for them than aspirin.

“If a patient is older, morbidly obese and you can tell they will be slower to recover, that patient probably is not a good choice for aspirin,” Dr. Westrich explains.

Dr. Parvizi says the bottom line is, if you or a loved one has a joint replacement planned, find out what drugs the doctors plan to use.

“Patients should be aware, and if they are receiving anything other than aspirin, they should ask why they are receiving the aggressive agents. They need to be engaged in the process,” Dr. Parvizi says.

Dr. Westrich agrees that this should be something patients bring up with their surgeons. “They should be asking what they are using after surgery,” says Dr. Westrich. “I will talk with patients about this, and if they are at standard risk I will tell them we use aspirin routinely.”