A knee-replacement operation is a common and not particularly dangerous procedure—but it can turn deadly if a blood clot forms in a leg vein. To prevent this, knee-replacement patients are usually prescribed blood thinners after their surgeries. However, anticoagulant drugs can be complicated to administer and monitor—and expensive. New research finds that a drugstore alternative works just as well…plus, it’s much cheaper and easier to use.

Venous thromboembolism (VTE)—the medical term for the condition that causes blood clots—in a leg vein is the most feared complication for the 700,000 Americans who undergo total knee replacements every year. If the clot travels to the lungs, it can cause a pulmonary embolism, which is fatal up to 30% of the time. But while guidelines strongly recommend an anticoagulant drug post-surgery, there is no clarity as to which anticoagulant is best.

Anticoagulant options include heparin, warfarin (Coumadin), a relatively new class of medications called factor Xa inhibitors (such as rivaroxaban, apixaban andedoxaban) and aspirin. Heparin is given by injection. Warfarin requires frequent blood tests to check that blood levels are high enough to be therapeutic but not so high as to cause internal bleeding…plus patients have to limit consumption of leafy greens and other vitamin K–containing foods. And factor Xa inhibitors are expensive—about $400 per month. Aspirin costs about $4 for a month’s supply, and you just swallow a tablet.

Researchers from the University of Michigan Health System wanted to see if aspirin alone would be effective at preventing VTE after knee replacement…and how aspirin’s increased risk for bleeding compared with increased bleeding risk for other anticoagulants.

The study included more than 40,000 patients at 29 Michigan hospitals who had had a total knee replacement. Among patients who took anticoagulants after their surgeries, 31% took only aspirin…55% had only another anticoagulant…and 13% had both aspirin and another anticoagulant. About 2% of the patients did not take any anticoagulation. All the patients were followed for 90 days after their surgeries, during which time 1.4% of the patients were diagnosed with VTE…

  • Patients who did not take an anticoagulant had the highest rate of VTE—nearly 5%.
  • Of patients taking an anticoagulant or anticoagulant combo, rate of VTE was 1.4% for patients taking an anticoagulant alone…1.3% for patients taking both an anticoagulant and aspirin…and 1.2% for patients taking aspirin alone.
  • Bleeding occurred in about 1% of all the patients—1.5% of patients who did not take any anticoagulant…1.1% of those taking an anticoagulant…1.4% of those taking both aspirin and an anticoagulant…and 0.9% of those taking only aspirin.

The results of this study further reinforce the need for some kind of anticoagulant after surgery. But these results also demonstrate that the anticoagulant doesn’t have to be an expensive, complicated prescription drug—drugstore aspirin, is simpler, cheaper and just as safe and effective.

Related Articles