Baby aspirin for extended DVT prophylaxis after elective hip and knee arthroplasty

By Drs. Terence Yung (biography, no disclosures) and Tony Wan (biography and disclosures) I have received unrestricted educational grants from Bayer and Servier. Mitigating potential bias: only published trial data is presented.

What I did before

After major elective orthopedic surgeries, patients have increased risk of developing venous thromboembolism and so current practice suggests some form of chemical prophylaxis regimen. Typically, the DVT prophylaxis regimen extends beyond the initial hospitalization and continues after discharge. Total duration of prophylaxis is recommended to be 14 days for elective knee replacement and 35 days for elective hip replacement. In recent years ever since the publication of the RECORD1-4 trials^1-4, rivaroxaban 10mg has been used in preference over low molecular weight heparin for extended DVT prophylaxis in this setting. This is driven by possible better outcomes (i.e. lower VTE) and also lower cost compared to low molecular weight heparin. In fact, in BC, special authority coverage is available for the use of rivaroxaban 10mg for this purpose. However, this practice is likely going to change since the publication of the EPCAT II trial⁵.

What changed my practice

The EPCAT II was a multicentre double-blind randomized control trial comparing rivaroxaban 10mg a day to aspirin 81mg a day starting from postoperative day 6 for DVT prophylaxis. Between and including postoperative day 1 to 5, patients received rivaroxaban 10mg a day for DVT prophylaxis. Once randomized, patients received either rivaroxaban 10mg a day or aspirin 81mg a day for additional 9 days for elective knee arthroplasty and 30 days for elective hip arthroplasty. The primary outcome was symptomatic VTE including above knee DVT and pulmonary embolism in the 90-day follow-up period. Note that these events were not screened but rather, investigation were undertaken when patients presented with symptoms. Safety outcome include major and minor bleeding as defined by the research protocol.

A total of 3427 patients were randomized in the trial. 53% underwent total hip arthroplasty with the rest being total knee arthroplasty. The two groups have similar baseline demographics. By 90-day follow-up period, symptomatic VTE developed in 0.64% in the aspirin group and 0.70% in the rivaroxaban group (p=0.84). Major bleeding events occurred in 0.47% in the aspirin group and 0.29% in the rivaroxaban group (p=0.42). The conclusion from this trial is after a minimum of 5 days of rivaroxaban 10mg daily, the remaining duration of DVT prophylaxis can be safely completed by aspirin 81mg daily, which is a much cheaper alternative.

There are a couple of caveats however. First of all, this trial enrolled only elective hip and knee arthroplasty and excluded surgeries involving fracture and so the data cannot be extrapolated to this latter population. Secondly, patients with greater VTE risks such as those with active cancer are excluded. Obese patients also have greater VTE risk and they are under-represented in the study population. In addition, overall the VTE rate is low in both groups compared to the literature, which could be due to a lower risk population. It is also interesting to note that 50-52% of the patients received pneumatic compression devices in addition to the chemical DVT prophylaxis in the initial period and more than 50% of the patients received tranexamic acid. Finally, for those who are chronically on low-dose aspirin for other reasons, they should receive double dose in the extended DVT prophylaxis course.

Many previous studies on DVT prophylaxis after major elective orthopedic surgeries were sponsored by the industry. The EPCAT II trial was designed by the authors and supported by the Canadian Institutes of Health Research (CIHR).

What I do now

For those who had an elective hip or knee arthroplasty who have no other risk factors for VTE, after initial 5 days of DVT prophylaxis with rivaroxaban 10mg a day, I complete the remaining DVT prophylaxis with aspirin 81mg once daily for an additional 30 days for hip arthroplasty and 9 days for knee arthroplasty. Those who already were on once-daily 81mg aspirin prior to surgery will receive 162mg aspirin once daily instead in this period.

References

1. Eriksson BI, Borris LC, Friedman RJ, et al. Rivaroxaban versus enoxaparin for thromboprophylaxis after hip arthroplasty. The New England Journal of Medicine. 2008;358(26):2765-2775. doi: 10.1056/NEJMoa0800374 (View)
2. Kakkar AK, Brenner B, Dahl OE, et al. Extended duration rivaroxaban versus short-term enoxaparin for the prevention of venous thromboembolism after total hip arthroplasty: A double-blind, randomised controlled trial. The Lancet. 2008;372(9632):31-39. doi: 10.1016/S0140-6736(08)60880-6 (view with CPSBC or UBC)
3. Lassen MR, Ageno W, Borris LC, et al. Rivaroxaban versus enoxaparin for thromboprophylaxis after total knee arthroplasty. The New England Journal of Medicine. 2008;358(26):2776-2786. doi: 10.1056/NEJMoa0800374 (view)
4. Turpie AG, Lassen MR, Davidson BL, et al. Rivaroxaban versus enoxaparin for thromboprophylaxis after total knee arthroplasty (RECORD4): A randomised trial. The Lancet. 2009;373(9676):1673-1680. doi: 10.1016/S0140-6736(09)60734-0 (view with CPSBC or UBC)
5. Anderson DR, Dunbar M, Murnaghan J, et al. Aspirin or rivaroxaban for VTE prophylaxis after hip or knee arthroplasty. The New England Journal of Medicine. 2018;378(8):699-707. doi: 10.1056/NEJMoa1712746 (view)

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Baby aspirin for extended DVT prophylaxis after elective hip and knee arthroplasty

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