When to initiate enoxaparin (Lovenox) in a patient with a goal INR of 2.5-3.5 undergoing a 4-day warfarin (Coumadin) hold prior to a procedure?

Initiating Enoxaparin (Lovenox) for Patients with Goal INR 2.5-3.5 During Warfarin Hold

For a patient with a goal INR of 2.5-3.5 undergoing a procedure with a 4-day warfarin hold, enoxaparin (Lovenox) should be initiated when the INR falls below 2.0, which typically occurs 48 hours after stopping warfarin (day -2).

Bridging Protocol Based on Thrombotic Risk

The timing of enoxaparin initiation depends on the patient's underlying thrombotic risk, which can be determined by the indication for anticoagulation:

High Thrombotic Risk Patients

• Patients with mechanical mitral valves
• Patients with mechanical aortic valves with risk factors
• Recent thromboembolism (within 3 months)

For these patients:

• Stop warfarin 4-5 days before procedure (day -4)
• Start therapeutic enoxaparin when INR falls below 2.0 (typically day -2)
• Last dose of enoxaparin should be given on the morning of the day before procedure (day -1)
• Hold enoxaparin on the day of procedure (day 0)
• Resume warfarin evening of procedure if hemostasis achieved
• Resume therapeutic enoxaparin 48 hours post-procedure if hemostasis is assured 1

Moderate Thrombotic Risk Patients

• Patients with bileaflet mechanical aortic valves without risk factors
• Atrial fibrillation with multiple risk factors

For these patients:

• Stop warfarin 4-5 days before procedure (day -4)
• Consider prophylactic dose enoxaparin when INR falls below 2.0
• Resume warfarin evening of procedure if hemostasis achieved
• Consider prophylactic enoxaparin 12 hours post-procedure 1

Low Thrombotic Risk Patients

• Atrial fibrillation with few risk factors
• Older (>3 months) venous thromboembolism

For these patients:

• Stop warfarin 4-5 days before procedure (day -4)
• No bridging therapy needed
• Resume warfarin evening of procedure if hemostasis achieved 1

Dosing Considerations for Enoxaparin

Therapeutic Dosing (for high-risk patients):

• 1 mg/kg subcutaneously every 12 hours, or
• 1.5 mg/kg subcutaneously once daily

Prophylactic Dosing (for moderate-risk patients):

• 40 mg subcutaneously once daily, or
• 30 mg subcutaneously twice daily 1

Important Considerations

1. Higher INR Target (2.5-3.5): The higher target INR of 2.5-3.5 typically indicates a mechanical heart valve in the mitral position or an older generation mechanical valve, which carries higher thrombotic risk and requires more aggressive bridging 1.

2. Renal Function: Adjust enoxaparin dose for patients with renal impairment (CrCl <30 mL/min) 1.

3. Avoid Enoxaparin in Certain Cases: The FDA and manufacturer warn against using enoxaparin for thromboprophylaxis in patients with mechanical heart valves 1.

4. Post-Procedure Management: The timing of resuming therapeutic anticoagulation depends on the bleeding risk of the procedure. For high bleeding risk procedures, delay therapeutic anticoagulation for 48-72 hours 1.

5. Monitoring: While routine coagulation monitoring is not required for enoxaparin, consider anti-Xa levels in patients with renal impairment, extremes of body weight, or prolonged therapy 1.

Common Pitfalls to Avoid

• Inadequate Bridging Duration: Ensure enoxaparin is started when INR falls below 2.0, not just on a fixed day
• Resuming Full Anticoagulation Too Early: This can lead to post-procedural bleeding
• Delaying Anticoagulation Too Long: This increases thrombotic risk, especially in high-risk patients
• Using Prophylactic Dosing for High-Risk Patients: High-risk patients require therapeutic dosing
• Overlooking Drug Interactions: Certain medications may affect warfarin metabolism when restarting therapy

By following this protocol, you can minimize both thrombotic and bleeding risks during the perioperative period for patients requiring temporary interruption of warfarin therapy.