What is the process of a heparin (unfractionated heparin) bridge for patients on oral anticoagulation therapy?

Heparin Bridging Therapy: Process and Management

Heparin bridging therapy is a temporary anticoagulation strategy that maintains anticoagulation during the perioperative period when oral anticoagulants must be interrupted for procedures, primarily using parenteral unfractionated heparin (UFH) to minimize thromboembolic risk while allowing for surgical intervention. 1, 2

Indications for Bridging

Bridging therapy should be considered for patients at high thromboembolic risk:

• Mechanical mitral valve replacement
• Older-generation mechanical aortic valve replacement
• Mechanical aortic valve with additional risk factors for thromboembolism
• Recent venous thromboembolism (<3 months)

Bridging is generally not recommended for:

• Patients with bileaflet mechanical aortic valve without additional risk factors 1, 2
• Most patients with non-valvular atrial fibrillation (based on BRIDGE trial findings) 2

Bridging Process with Unfractionated Heparin (UFH)

Pre-Procedure Phase

1. Discontinue oral anticoagulant (warfarin): Stop 5 days before procedure 1, 3
2. Initiate UFH: Begin intravenous UFH 3-4 days before procedure when INR falls below therapeutic range 1, 2
3. Dosing: Initial dose of 5,000 units by IV injection, followed by continuous infusion of 20,000-40,000 units/24 hours 4
4. Monitoring: Adjust dose to maintain APTT at 1.5-2 times normal 4
5. Pre-procedure discontinuation: Stop UFH infusion 4-6 hours before procedure 1, 2

Post-Procedure Phase

1. Resume UFH: Based on procedural bleeding risk:
   • Low bleeding risk: Resume 24 hours after procedure
   • High bleeding risk: Delay resumption for 48-72 hours 1, 2
2. Restart oral anticoagulant: Begin warfarin evening of or day after procedure at usual maintenance dose 2
3. Continue UFH: Maintain until INR reaches therapeutic range 2, 4
4. Monitoring: Continue periodic platelet counts, hematocrits, and tests for occult blood 4

Alternative Bridging with LMWH

For outpatient management, LMWH (e.g., enoxaparin) can be used instead of UFH:

• High thromboembolic risk: 70 anti-factor Xa U/kg (approximately 1mg/kg) twice daily 3
• Moderate to low risk: Prophylactic once-daily doses 3
• Renal impairment: Dose reduction to 1mg/kg once daily for CrCl 20-50 ml/min 5

Practical Considerations

• For emergency procedures requiring immediate reversal of anticoagulation, 4-factor prothrombin complex concentrate is recommended 1
• Bridging therapy increases bleeding risk 2-3 fold without significant reduction in thromboembolic events in most patients 6
• Major bleeding is more common with twice-daily LMWH regimens (used for high-risk patients) 3
• The CHADS₂ score has been identified as an independent hemorrhagic risk factor during bridging 5

Common Pitfalls

• Unnecessary bridging: Most patients with atrial fibrillation and bileaflet mechanical aortic valves without risk factors don't require bridging 2, 6
• Premature resumption: Restarting therapeutic anticoagulation too soon after high bleeding risk procedures increases bleeding complications 1, 2
• Inadequate monitoring: Failure to monitor coagulation parameters during UFH administration can lead to sub- or supra-therapeutic anticoagulation 4
• Overlooking renal function: Patients with renal impairment require dose adjustments when using LMWH 5

Heparin bridging therapy requires careful assessment of both thromboembolic and bleeding risks, with individualized approaches based on patient characteristics and procedural factors. The evidence increasingly suggests limiting bridging to only those patients at highest thromboembolic risk, as unnecessary bridging increases bleeding complications without reducing thromboembolic events.