What are the guidelines for prescribing bridge prescriptions, specifically low-molecular-weight heparin (LMWH) for patients on warfarin (coumarin) therapy?

Guidelines for Prescribing Bridge Anticoagulation with LMWH for Patients on Warfarin

For patients with atrial fibrillation and high thrombotic risk who require temporary interruption of warfarin, bridging therapy with low-molecular-weight heparin (LMWH) is recommended, though decisions should balance stroke and bleeding risks on an individual basis. 1

Patient Risk Stratification for Bridging

High Thrombotic Risk (Bridging Recommended)

• Patients with mechanical heart valves 1
• Recent stroke or TIA within 3 months 1
• CHADS₂ score of 5 or 6 1
• Rheumatic valve disease 1
• Recent venous thromboembolism (<3 months) 2
• Antiphospholipid syndrome with recent thrombosis 2

Low/Intermediate Thrombotic Risk (Bridging Generally Not Recommended)

• Most patients with atrial fibrillation without the above risk factors 1
• The BRIDGE trial demonstrated that absence of bridging was non-inferior to bridging with LMWH for prevention of arterial thromboembolism in most AF patients and significantly decreased bleeding risk 1

Bridging Protocol

For Patients Requiring Bridging:

1. Warfarin Discontinuation:

   • Stop warfarin 5 days before the procedure 2
   • Monitor INR until <2.0 before initiating bridging therapy

2. LMWH Administration:

   • Begin LMWH when INR falls below 2.0 2
   • Standard dosing: 1 mg/kg twice daily or 1.5 mg/kg once daily 2
   • Last dose of LMWH should be given 24 hours before the procedure 2

3. Post-Procedure Management:

   • Resume warfarin evening of or day after procedure at usual maintenance dose 2
   • Resume LMWH 24-48 hours after procedure if hemostasis is adequate 2
   • Continue LMWH until INR reaches therapeutic range (2.0-3.0) 2

Special Considerations

Direct Oral Anticoagulants (DOACs)

• Unlike warfarin, DOACs generally do not require bridging due to their shorter half-lives 2
• For dabigatran with reduced renal function (CrCl 30-50 mL/min), last dose should be 5 days before procedure 1
• Idarucizumab is recommended for emergency reversal of dabigatran 1
• Andexanet alfa can be useful for reversal of rivaroxaban and apixaban in emergency situations 1

Bleeding Risk Management

• Bridging therapy increases bleeding risk without reducing thromboembolic events in most patients 2
• Multiple studies have demonstrated increased post-procedural bleeding with bridging therapy, particularly after colonoscopy polypectomy 1
• The BRIDGE trial showed a significantly higher rate of major bleeding with bridging (3.2%) compared to no bridging (1.3%) 3

Common Pitfalls to Avoid

1. Unnecessary bridging in low-risk patients, which increases bleeding risk without reducing thromboembolism
2. Inadequate risk assessment before deciding on bridging therapy
3. Resuming anticoagulation too early after procedures with high bleeding risk
4. Failure to adjust dosing based on renal function, especially for dabigatran
5. Not considering patient-specific factors like prior bleeding history, medication interactions, and compliance

Algorithm for Decision-Making

1. Assess thrombotic risk using validated tools (CHADS₂, CHA₂DS₂-VASc)
2. Evaluate bleeding risk of the procedure
3. For high thrombotic risk patients: implement bridging protocol
4. For low/intermediate risk: simple interruption of warfarin without bridging
5. Tailor post-procedure anticoagulation resumption based on hemostasis

Remember that the evidence strongly suggests most patients with atrial fibrillation do not benefit from bridging therapy, and it may actually increase harm through bleeding complications.