What is the recommended heparin (unfractionated heparin) dose for treating pulmonary embolism?

Heparin Dosing for Pulmonary Embolism

For pulmonary embolism treatment, unfractionated heparin should be administered as an initial intravenous bolus of 5,000-10,000 IU (or weight-based at 80 IU/kg), followed by a maintenance infusion of 18 IU/kg/hour (weight-based) or 1,300 IU/hour (standard), with dose adjustments to maintain APTT at 1.5-2.5 times control value (45-75 seconds). 1

Dosing Protocol

Initial Bolus Dose

• Standard approach: 5,000-10,000 IU IV bolus 1, 2
• Weight-based approach: 80 IU/kg IV bolus 1

Maintenance Infusion

• Standard approach: 1,300 IU/hour continuous IV infusion 1
• Weight-based approach: 18 IU/kg/hour continuous IV infusion 1

APTT Monitoring Schedule

1. After initial bolus: Check APTT in 4-6 hours 1
2. After any dose change: Check APTT in 6-10 hours 1
3. Once therapeutic: Check APTT daily 1

Dose Adjustment

• Target APTT: 1.5-2.5 times control value (typically 45-75 seconds) 1, 2
• Adjust infusion rate based on APTT results to maintain therapeutic range

Treatment Duration

• Continue heparin for 5 days after starting warfarin 1
• Discontinue heparin when INR reaches at least 2.0 1

Common Pitfalls and Caveats

• Inadequate initial dosing: Failure to achieve therapeutic APTT within first 24 hours is associated with 25% risk of recurrent thromboembolism 3
• Monitoring errors: Relying solely on fixed dosing without APTT monitoring can lead to treatment failure or bleeding complications 2
• Heparin resistance: Some patients with PE may require higher doses due to increased clearance 4
• Drug preparation errors: Always confirm correct heparin concentration to avoid medication errors 2
• Administration route: Avoid intramuscular injections due to risk of hematoma formation 2

Special Considerations

• Thrombolysis: If thrombolytic therapy is planned, stop heparin infusion during thrombolysis and resume at maintenance dose afterward 1
• High bleeding risk: Consider more frequent APTT monitoring in patients with risk factors for bleeding
• Transitioning to oral anticoagulation: Overlap heparin with warfarin for at least 4-5 days and continue heparin until INR is therapeutic (≥2.0) 1, 3

The weight-based dosing approach (80 IU/kg bolus followed by 18 IU/kg/hour) may provide more predictable anticoagulation compared to fixed dosing, particularly in patients with extremes of body weight 1, 2.