When can aspirin be discontinued after a total knee replacement if it is being used for venous thromboembolism prophylaxis?

When to Stop Aspirin After Total Knee Replacement

Aspirin used for VTE prophylaxis after total knee arthroplasty should be continued for a minimum of 4 weeks postoperatively, with extended duration up to 6 weeks being reasonable for standard-risk patients. 1, 2

Duration of Prophylaxis

Standard recommendation is 4-6 weeks of aspirin therapy following total knee replacement. 1, 3 This duration is supported by:

• The American College of Chest Physicians (ACCP) guidelines recommend a minimum of 7-10 days of thromboprophylaxis for lower extremity orthopedic surgery, with extended prophylaxis up to 5 weeks for total hip replacement 4
• Current practice patterns demonstrate safety and efficacy with 4-6 weeks of aspirin continuation after TKA 3, 5, 6
• The risk of VTE persists for up to 2 months following major orthopedic surgery, particularly in patients with continued immobility 4

Optimal Dosing Regimen

Low-dose aspirin (81 mg twice daily) is superior to higher doses and should be the preferred regimen. 7, 5, 6

• 81 mg aspirin BID resulted in significantly lower VTE rates (0.23%) compared to 325 mg aspirin BID (1.41%, p<0.001) 7
• Low-dose aspirin (81 mg BID) demonstrated significantly lower bleeding complications (2.5%) versus 325 mg daily (7.6%, p=0.0029) with equivalent VTE protection 6
• Symptomatic DVT rates were lower with 81 mg BID (0.3%) compared to 325 mg BID (1.4%, p=0.0009) 5

Initial Anticoagulation Strategy

Patients should receive initial enoxaparin for 5 days before transitioning to aspirin monotherapy. 3, 8

• The EPCAT II trial demonstrated that 5 days of rivaroxaban 10 mg followed by aspirin 81 mg daily was non-inferior to continued rivaroxaban for extended prophylaxis 8
• Current HSE guidelines recommend 72 hours of enoxaparin followed by 4 weeks of aspirin 3
• This bridging strategy balances immediate postoperative thrombotic risk with long-term prophylaxis needs 8

Special Circumstances Requiring Continuation

Aspirin MUST be continued indefinitely in patients with pre-existing cardiovascular indications, regardless of the knee replacement. 4, 2

Patients with coronary stents:

• Aspirin continuation is non-negotiable throughout the perioperative period 2
• Premature discontinuation markedly increases risk of catastrophic stent thrombosis, death, and MI 2
• This applies to both bare-metal and drug-eluting stents 2

Patients on aspirin for secondary cardiovascular prevention:

• Aspirin should NOT be discontinued preoperatively when prescribed for cardiovascular prevention, history of ischemic stroke, or lower extremity artery disease 4
• Discontinuing antiplatelet therapy increases absolute risk of stroke recurrence or cardiovascular events by approximately 2% within 30 days 4, 2
• Continuing aspirin may increase procedural bleeding frequency (relative risk 1.5) but does not increase severity of bleeding complications or perioperative mortality 4, 2

Critical Pitfalls to Avoid

Do not stop aspirin prematurely in the first 4 weeks after TKA. 1, 3 The risk of VTE remains elevated throughout this period, and early discontinuation eliminates prophylactic benefit.

Do not confuse VTE prophylaxis duration with cardiovascular aspirin therapy. 4, 2 Patients on aspirin for coronary disease, prior stroke, or peripheral arterial disease require lifelong continuation regardless of the knee replacement.

Do not use aspirin as the sole initial prophylaxis immediately postoperatively. 1 Initial anticoagulation with LMWH or rivaroxaban for 5 days provides superior immediate protection before transitioning to aspirin 3, 8.

Do not prescribe high-dose aspirin (325 mg) when low-dose (81 mg BID) is more effective and safer. 7, 5, 6 The evidence consistently demonstrates superior outcomes with 81 mg twice daily dosing.

Resumption After Temporary Discontinuation

If aspirin must be stopped for a surgical procedure, it should be resumed within 24 hours postoperatively once adequate hemostasis is achieved. 2 For patients requiring aspirin for cardiovascular indications, gaps in dosing >48 hours may lead to loss of tolerance in certain populations 4, though this primarily applies to aspirin-exacerbated respiratory disease rather than VTE prophylaxis.