Heparin Dosing for IVC, RA, and Pulmonary Artery Clots
For patients with clots in the inferior vena cava (IVC), right atrium (RA), or pulmonary artery, the recommended heparin dosing is a weight-based regimen of 80 units/kg IV bolus followed by 18 units/kg/hour as continuous IV infusion, with dose adjustments based on aPTT monitoring. 1
Initial Dosing Options
Weight-Based Approach (Preferred)
- Initial IV bolus: 80 units/kg 1
- Continuous IV infusion: 18 units/kg/hour 1
- This regimen has been shown to achieve therapeutic anticoagulation more rapidly and with lower recurrence rates of thromboembolism compared to fixed-dose regimens 2
Fixed-Dose Alternative
- Initial IV bolus: 5,000 units 1
- Continuous IV infusion: at least 32,000 units/day 1
- This approach is less optimal than weight-based dosing but may be used when patient weight is unavailable 1
Monitoring and Dose Adjustments
- Target aPTT: 1.5-2.5 times control value (typically 45-75 seconds) 1
- First aPTT check: 4-6 hours after initial bolus 1
- Subsequent monitoring: After any dose change (6-10 hours later) and daily when in therapeutic range 1
- Adjust dose according to aPTT results using a standardized protocol 1:
- aPTT < 35 seconds: 80 units/kg bolus, increase infusion by 4 units/kg/hour 1
- aPTT 35-45 seconds: 40 units/kg bolus, increase infusion by 2 units/kg/hour 1
- aPTT 46-70 seconds (therapeutic): No change 1
- aPTT 71-90 seconds: Decrease infusion by 2 units/kg/hour 1
- aPTT > 90 seconds: Hold infusion for 1 hour, then decrease by 3 units/kg/hour 1
Duration of Therapy
- Continue heparin for at least 5 days 1
- Overlap with warfarin for at least 4-5 days 3
- Discontinue heparin when INR is ≥ 2.0 for at least 24 hours 1
Special Considerations
- Early achievement of therapeutic aPTT (within 24 hours) is associated with lower mortality in pulmonary embolism patients 1
- Patients with massive or submassive pulmonary embolism may require thrombolytic therapy before or concurrent with heparin 1
- Monitor platelet counts, hematocrit, and occult blood in stool throughout therapy 4
- Be vigilant for heparin-induced thrombocytopenia (HIT), especially if new thrombosis develops during treatment 5
Common Pitfalls to Avoid
- Using fixed-dose regimens rather than weight-based dosing can lead to subtherapeutic anticoagulation and increased risk of recurrent thromboembolism 1, 2
- Failure to achieve therapeutic aPTT within 24 hours is associated with higher mortality in pulmonary embolism 1
- Subcutaneous administration of heparin is less effective than IV infusion for treatment of venous thromboembolism due to reduced bioavailability 1
- Inadequate monitoring of aPTT can lead to either subtherapeutic anticoagulation (risking clot progression) or excessive anticoagulation (increasing bleeding risk) 1
- Discontinuing heparin before warfarin has reached therapeutic levels (INR ≥ 2.0) can lead to treatment failure 1, 3