Should I bridge with Low Molecular Weight Heparin (LMWH), such as enoxaparin (Lovenox), until the INR reaches 2.0 while adjusting the warfarin dose?

Immediate LMWH Bridging is Strongly Recommended

Yes, you should immediately initiate therapeutic-dose LMWH (enoxaparin) bridging while adjusting warfarin, given this patient's extremely high thromboembolic risk profile and current subtherapeutic INR of 1.7. This patient experienced a catastrophic arterial embolism with critical ischemia requiring amputation directly attributable to warfarin interruption, placing them in the highest risk category for recurrent thromboembolism.

Risk Stratification: Highest Thromboembolic Risk

This patient falls into the highest risk category based on multiple factors 1:

• Recent arterial embolism with critical ischemia (within weeks of warfarin interruption)
• History of both venous (PE/DVT) and arterial thromboembolism
• Proven thrombotic event during recent anticoagulation interruption
• Currently subtherapeutic INR (1.7) requiring therapeutic adjustment

Patients at high risk (>10% annual thrombotic risk) requiring bridging include those with venous thromboembolic events within the last 3 months or mechanical heart valves 1. Your patient's recent arterial embolism places them in an even higher risk category.

LMWH Bridging Protocol

Immediate Initiation

Start therapeutic-dose enoxaparin immediately while the INR remains subtherapeutic 1:

• Enoxaparin 1 mg/kg subcutaneously twice daily (preferred for high-risk patients) 1
• Alternative: Enoxaparin 1.5 mg/kg once daily 1, 2
• Continue LMWH overlap with warfarin for minimum 5 days 1

Warfarin Dose Adjustment

Increase warfarin dose aggressively from current 2.5 mg 1:

• Consider loading with 5-10 mg daily depending on patient age and comorbidities 1
• Younger patients (<60 years) can tolerate 10 mg loading doses 1
• Older or hospitalized patients should receive 5 mg 1

INR Monitoring During Bridging

Check INR daily until therapeutic range achieved 3:

• Do NOT discontinue enoxaparin until INR is 2.0-3.0 on 2 consecutive measurements 1, 3
• After achieving therapeutic INR, check 2-3 times weekly for 1-2 weeks 3
• LMWH must overlap warfarin until INR ≥2.0 for at least 24 hours 1

Critical Timing Considerations

When to Stop LMWH

The minimum overlap period is 5 days, but continuation depends on INR response 1:

• Continue enoxaparin for at least 5 days AND until INR therapeutic x 2 consecutive days 1
• In high-risk patients like yours, err on the side of longer overlap 1
• The European Heart Journal emphasizes not stopping LMWH prematurely 3

Avoiding the Pitfall That Led to Amputation

The catastrophic outcome your patient experienced (arterial embolism → critical ischemia → amputation) occurred because warfarin was held for 5 days without bridging 1. This exact scenario is what bridging therapy is designed to prevent in high-risk patients 1.

Evidence Supporting Bridging in This Case

While recent evidence questions routine bridging for low-risk patients (particularly atrial fibrillation) 1, 4, guidelines uniformly support bridging for high-risk patients 1:

• Patients with recent VTE (within 3 months) require bridging 1
• Mechanical heart valve patients require bridging 1
• Your patient's recent arterial embolism with limb loss represents an even higher risk 1

The AAGBI guidelines specifically state that bridging is recommended for patients at high risk (>10% annual thrombotic risk) 1. A Swedish registry study showing no benefit from bridging 4 included predominantly lower-risk patients and cannot be extrapolated to your patient's extreme-risk profile.

Special Monitoring Considerations

Renal Function

• Check creatinine clearance before dosing 1
• If CrCl <30 mL/min, use caution with LMWH or consider unfractionated heparin 1

Platelet Monitoring

• Not routinely required for LMWH (lower HIT risk than UFH) 1
• Consider monitoring if prolonged therapy expected 1

Common Pitfalls to Avoid

1. Waiting for INR to rise before starting LMWH - Start immediately 1
2. Stopping LMWH after only 5 days if INR not yet therapeutic - Must have 2 consecutive therapeutic INRs 1, 3
3. Using prophylactic-dose LMWH - This patient requires full therapeutic dosing 1
4. Single INR check before stopping LMWH - Requires 2 consecutive therapeutic measurements 3

The devastating outcome your patient already suffered (amputation) underscores the critical importance of aggressive bridging in this highest-risk scenario. The 2.5 mg warfarin dose is likely insufficient and requires upward titration with daily INR monitoring while maintaining therapeutic LMWH coverage 1, 3.