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#336 ASA in TKA and THA Patients: Back to the future for VTE prophylaxis? (Free)

For total knee (TKA) or hip arthroplasty (THA) patients, does ASA result in similar symptomatic venous thromboembolism (VTE) and bleeding rates as low molecular weight heparins (LMWHs) or direct-acting oral anticoagulants (DOACs)?

After initial treatment with 10-days of LMWHs or 5-days of DOACs, switching to ASA results in similar VTE and bleeding rates. Starting ASA alone immediately after surgery results in more VTEs (3.5% versus 1.8%) than LMWH. Due to cost and ease of use, after initial treatment with LMWHs or DOACs, patients can transition to ASA for the remainder of their VTE prophylaxis.

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  • From three publicly funded, non-inferiority randomized controlled trials. Only symptomatic VTEs reported.
  • After initial treatment with anti-coagulants:
    • ASA versus LMWH:1 778 Canadian THA patients; received dalteparin for 10 days then randomized to dalteparin or ASA 81mg daily for another 28 days. Study terminated early due to recruitment challenges. At 3 months:
      • Symptomatic VTE, major and relevant non-major bleeding: Not statistically different.
    • ASA versus DOAC:2 3424 Canadian THA/TKA patients; received rivaroxaban for 5 days then randomized to rivaroxaban or ASA 81mg daily for 9 (knee) or 30 (hip) additional days. At 3 months:
      • Symptomatic VTE, major and relevant non-major bleeding: Not statistically different.
    • ASA versus LMWH immediately after surgery:3
      • 9711 Australian TKA/THA patients randomized to ASA 100mg daily or enoxaparin 40mg/day for 14 (knee) or 35 (hip) days. Study stopped early for LMWH superiority. At 90 days:
        • Symptomatic VTE: ASA 3.5% versus enoxaparin 1.8%, statistically different.
        • Major bleeding, all-cause mortality: No difference.
  • Without prophylaxis, ~4% of arthroplasty patients will develop a symptomatic VTE.4
  • Guidelines recommend anticoagulation for 14 (knee) and 35 (hip) days with one of LMWH, DOAC, Vitamin K antagonist, or ASA.4,5
  • Medication Cost (30 days):6
    • LMWH: $200-300
    • DOAC: $50-100
    • ASA: $5

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  • Michael R Kolber BSc MD CCFP MSc
  • Robert E Korbyl MD FRCS(C)
  • Tony Nickonchuk BScPharm

1. Anderson DR, Dunbar MJ, Bohm ER, et al. Ann Intern Med. 2013; 158:800-806.

2. Anderson DR, Dunbar M, Murnaghan J, et al. N Engl J Med. 2018; 378:699-707

3. Sidhu VS on behalf of Cristal Study Group. JAMA 2022; 328 (8): 719-727

4. Falck-Ytter Y, Francis CW, Johanson NA, et al. Chest 2012; 141(2 Suppl):e278S-325S

5. Anderson DR, Morgan GP, Bennett C, et al. Blood Adv. 2019;3(23):3898-3944.

6. Alberta Blue Cross Interactive Drug Benefit List for calculations. Available at: Accessed: 7 March 2023.

Authors do not have any conflicts of interest to declare.