Clinical question: What are rates of venous thromboembolism (VTE) and bleeding among adult patients receiving aspirin versus anticoagulants after major lower extremity orthopedic surgery?
Background: VTE is common after hip fracture surgery and elective total knee/hip arthroplasty. National guidelines recommend pharmacologic thromboprophylaxis but leave clinicians to select the specific agents. The efficiency and safety of aspirin in these patient populations, compared to other anticoagulants, has been a source of great controversy.
Study design: Meta-analysis.
Setting: Eight randomized trials in the U.S., Spain, Sweden, and Canada.
Synopsis: The trials included 1,408 subjects; aspirin was compared with other anticoagulants for VTE prevention and bleeding after major lower extremity orthopedic surgery. The primary outcome was the rate of proximal deep vein thrombosis (DVT). The different classes of anticoagulants included warfarin, heparin, low molecular weight heparin (LMWH), and danaparoid. Treatment duration was seven to 21 days with clinical follow-up extended up to six months.
Overall rates of DVT did not differ statistically between aspirin and anticoagulants (10.4% vs. 9.2%); however, the balance of risk versus benefit of aspirin compared to anticoagulation differed according to type of surgery; there was a nonsignificant trend favoring anticoagulation for VTE prevention following hip fracture repair, but no difference was found for knee/hip arthroplasty. The risk of bleeding was lower with aspirin than with anticoagulants following hip fracture repair (3.1% vs. 10%) and knee/hip arthroplasty (3.9% vs. 7.8%).
Rates of pulmonary embolism were too low in all the groups to provide reliable estimates.
Bottom line: Aspirin may be associated with higher risk of VTE following hip fracture repair compared to anticoagulants, although bleeding rates were substantially lower. Aspirin was similarly effective compared to anticoagulants for VTE prevention after knee/hip arthroplasty and may be associated with lower bleeding risk.
