What is the best option for Venous Thromboembolism (VTE) prophylaxis in a 75-year-old woman with a prosthetic aortic valve, hypertension, and a scheduled right hip hemiarthroplasty for a hip fracture?

Best Option for VTE Prophylaxis in a Patient with Hip Fracture and Prosthetic Aortic Valve

Enoxaparin 40 mg subcutaneously once daily is the best option for venous thromboembolism prophylaxis during hospitalization for this patient with a hip fracture and prosthetic aortic valve. 1

Rationale for Recommendation

Patient Risk Assessment

• 75-year-old female with:
  • Right hip fracture requiring hemiarthroplasty
  • Prosthetic aortic valve (significant risk factor)
  • Hypertension
  • Advanced age (additional risk factor)

Evidence-Based Selection Process

LMWH (Enoxaparin) as First-Line Option

Enoxaparin 40 mg once daily is recommended based on:

1. Guideline Support: The Mayo Clinic guidelines specifically recommend LMWH as a grade 1B recommendation for orthopedic surgery patients 1

2. Efficacy in Hip Fracture Surgery: Enoxaparin 40 mg once daily has demonstrated effective VTE prophylaxis in patients undergoing hip surgery with an acceptable bleeding risk profile 1, 2

3. Mechanical Valve Considerations: For patients with prosthetic heart valves requiring surgical procedures, LMWH is the preferred bridging therapy when warfarin must be discontinued 1

Why Not the Other Options?

1. Warfarin (5 mg daily):

   • Not recommended as primary VTE prophylaxis for orthopedic surgery patients 1
   • Requires several days to reach therapeutic levels, leaving patient unprotected during highest risk period
   • Requires frequent monitoring and dose adjustments

2. Rivaroxaban (10 mg daily):

   • Contraindicated in patients with mechanical heart valves 1
   • No evidence supporting safety in patients with prosthetic valves

3. Fondaparinux (2.5 mg twice daily):

   • Standard dosing is 2.5 mg once daily, not twice daily 1, 3
   • Less evidence for use in patients with prosthetic valves
   • Increased risk in patients with renal impairment, which is common in elderly patients 3

Implementation Considerations

Timing of Administration

• Begin enoxaparin 12 hours after surgery once hemostasis is achieved 1
• Continue throughout hospitalization and for 10-14 days post-surgery 1
• Consider extending prophylaxis up to 35 days for high-risk patients 1

Monitoring Requirements

• Check baseline CBC, platelet count, PT/aPTT, and renal function before initiating therapy 1
• Monitor platelet counts every 2-3 days from day 4-14 to screen for heparin-induced thrombocytopenia (HIT) 1
• Assess for signs of bleeding daily

Special Considerations for Prosthetic Valve

• The patient's prosthetic aortic valve requires careful management
• LMWH provides effective prophylaxis without interfering with valve function
• Mechanical compression devices can be added for enhanced protection if bleeding risk increases 1

Potential Pitfalls and Caveats

1. Weight-Based Dosing: Consider dose reduction to 30 mg daily if patient weighs less than 50 kg 4

2. Renal Function: Monitor renal function as enoxaparin clearance decreases with age and renal impairment 1

3. Bleeding Risk: Be vigilant for signs of bleeding, especially at the surgical site

4. Transition Planning: Consider transition to oral anticoagulation if long-term therapy is needed after discharge

5. Mechanical Prophylaxis: Consider adding intermittent pneumatic compression devices for enhanced protection, especially if pharmacologic prophylaxis must be temporarily held 1

By following these recommendations, you can provide optimal VTE prophylaxis for this high-risk patient while minimizing bleeding complications and protecting her prosthetic valve.