What is the best option for Venous Thromboembolism (VTE) prophylaxis in a 75-year-old woman with a history of bioprosthetic aortic valve replacement undergoing hip replacement surgery?

Best VTE Prophylaxis Option for Hip Fracture Surgery in a 75-Year-Old Woman with Bioprosthetic Aortic Valve

Apixaban 2.5 mg twice daily is the best option for venous thromboembolism prophylaxis in this 75-year-old woman with a bioprosthetic aortic valve undergoing hip fracture surgery. 1, 2

Rationale for Recommendation

Patient Risk Assessment

This patient has multiple high-risk factors for VTE:

• Age ≥75 years (significant risk factor)
• Hip fracture surgery (highest risk category)
• Reduced mobility following surgery
• History of cardiovascular disease (bioprosthetic aortic valve)

According to the risk stratification in the guidelines, this patient falls into the "highest risk" category with an estimated DVT risk of 40-80% without prophylaxis 1.

Considerations for Bioprosthetic Valve

• Patients with bioprosthetic valves (unlike mechanical valves) do not require long-term anticoagulation with warfarin 1
• The 2014 AHA/ACC guidelines indicate that bioprosthetic valves are recommended in patients >70 years of age 1
• For patients with bioprosthetic valves, anticoagulation with warfarin is typically only recommended for the first 3-6 months post-valve surgery 1

Evidence for Apixaban in Orthopedic Surgery

1. FDA Approval: Apixaban 2.5 mg twice daily is FDA-approved specifically for VTE prophylaxis in patients undergoing hip or knee replacement surgery 2

2. Efficacy: In orthopedic surgery patients, apixaban has demonstrated superior efficacy compared to enoxaparin in reducing the risk of VTE 2

3. Dosing for Orthopedic Surgery: The recommended dose is 2.5 mg twice daily, with the first dose 12-24 hours post-surgery 2

4. Duration: For hip fracture surgery, prophylaxis should be continued for 35 days 1

5. Favorable Risk Profile: Direct oral Xa inhibitors like apixaban have demonstrated a more favorable profile of VTE prevention with acceptable bleeding risk compared to LMWH 3

Alternative Options and Why They Are Less Optimal

Enoxaparin 40 mg daily

• While effective and recommended in guidelines, direct oral Xa inhibitors like apixaban have shown superior efficacy with a favorable bleeding risk profile 3
• Requires daily injections, which may affect patient compliance after discharge

Rivaroxaban 10 mg daily

• Also effective, but apixaban has comparable efficacy with potentially better bleeding risk profile
• Not specifically mentioned in the question options

Warfarin 5 mg daily

• Not recommended as first-line for VTE prophylaxis in orthopedic surgery 1
• Requires frequent INR monitoring and has unpredictable pharmacokinetics
• More challenging to manage in the perioperative setting
• Has a less favorable profile compared to LMWH and direct oral Xa inhibitors 3

Implementation Considerations

• Timing: First dose of apixaban should be given 12-24 hours after surgery when hemostasis is established 2
• Duration: Continue for 35 days post-surgery for hip fracture patients 1
• Monitoring: No routine coagulation monitoring is required 2
• Renal function: Consider dose adjustment if severe renal impairment

Potential Pitfalls and Caveats

• Spinal/epidural anesthesia: If neuraxial anesthesia is planned, timing of apixaban administration is critical to avoid spinal/epidural hematoma 2
• Drug interactions: Monitor for interactions with strong dual inhibitors of CYP3A4 and P-gp
• Bleeding risk: Although favorable, all anticoagulants carry bleeding risk that should be monitored
• Temporary interruption: If invasive procedures are needed during treatment, apixaban should be discontinued at least 24-48 hours prior depending on bleeding risk 2

In conclusion, apixaban 2.5 mg twice daily provides the optimal balance of efficacy and safety for VTE prophylaxis in this elderly patient undergoing hip fracture surgery with a history of bioprosthetic aortic valve replacement.