What is the approach to bridge anticoagulation (use of anticoagulant medications to bridge the period when a patient is not taking their regular oral anticoagulant), specifically the management and dosing of low molecular weight heparin (LMWH) such as enoxaparin (generic name), unfractionated heparin (UFH), and fondaparinux?

Bridge Anticoagulation Management

Bridging anticoagulation should be administered with therapeutic-dose low molecular weight heparin (LMWH) only in patients at high thromboembolic risk, while most patients on direct oral anticoagulants (DOACs) do not require bridging at all. 1

Patient Risk Stratification for Bridging

High Thromboembolic Risk (Consider Bridging)

• Venous thromboembolism within last 3 months 1
• Mechanical heart valves 1
• Atrial fibrillation with CHADS₂ score ≥5 1

Low to Moderate Thromboembolic Risk (Generally No Bridging)

• Most patients with atrial fibrillation 1
• VTE >3 months ago 1
• Patients on DOACs (no bridging needed due to short half-life) 2

Bridging Anticoagulant Options

Low Molecular Weight Heparin (LMWH)

• Preferred option for most patients requiring bridging 1
• Therapeutic dosing:
  • Enoxaparin 1 mg/kg twice daily or 1.5 mg/kg once daily
  • Dalteparin 100 IU/kg twice daily or 200 IU/kg once daily 1
• Renal adjustment: For CrCl 30-50 ml/min, consider once-daily dosing; for CrCl 20-29 ml/min, reduce dose by 50% 3
• Last preoperative dose: Administer approximately 24 hours before surgery rather than 12 hours before surgery to minimize bleeding risk 1

Unfractionated Heparin (UFH)

• Indications: Severe renal insufficiency or dialysis-dependent patients 1
• Dosing: IV infusion to achieve aPTT 1.5-2.0 times control 4
• Timing: Stop infusion 4-6 hours before surgery 1
• Alternative: Fixed-dose, weight-based SC regimen (250 IU/kg twice daily) for outpatient use 1

Fondaparinux

• Dosing: 2.5 mg SC once daily for prophylaxis 5
• Timing: Initial dose 6-8 hours after surgery when hemostasis established 5
• Duration: 5-9 days typically 5

Practical Bridging Protocol

For Warfarin Patients:

1. Preoperative Management:

   • Stop warfarin 5 days before procedure
   • Start LMWH 3 days before procedure (when INR falls below therapeutic range)
   • Administer last dose of LMWH 24 hours before procedure 1

2. Postoperative Management:

   • Low bleeding risk procedures: Resume LMWH 12-24 hours after procedure
   • High bleeding risk procedures: Delay LMWH resumption for 48-72 hours 1
   • Resume warfarin within 24 hours post-procedure when hemostasis is adequate
   • Continue LMWH until INR reaches therapeutic range (typically 2-3) 1

For DOAC Patients:

• No bridging needed in most cases 2
• Stop DOAC 2-5 days before procedure based on renal function and bleeding risk
• Resume DOAC 6-72 hours after procedure based on bleeding risk 2

Common Pitfalls and Caveats

• Premature LMWH resumption: Resuming therapeutic-dose LMWH too early (within 12 hours) after major surgery significantly increases bleeding risk (20% vs 0.7% for minor procedures) 1

• Residual anticoagulation: Over 90% of patients who receive LMWH 12 hours before surgery have detectable anticoagulant effects, with 34% having therapeutic levels at surgery 1

• Renal function impact: Patients with renal impairment have higher bleeding risk with standard LMWH doses. The CHADS₂ score has been identified as an independent hemorrhagic risk factor 3, 6

• Unnecessary bridging: Routine bridging in atrial fibrillation patients undergoing procedures is not recommended and may increase bleeding risk without reducing thrombotic events 1

• Outpatient vs inpatient: Bridging therapy can be safely performed in outpatient settings for appropriate candidates, reducing costs compared to inpatient management 7, 8

Remember that the decision to bridge should be based on balancing the individual patient's thromboembolic risk against their bleeding risk, with the understanding that unnecessary bridging may cause more harm than benefit.