Heparin Dosing and Administration for Thromboembolic Disorders
For therapeutic anticoagulation with unfractionated heparin (UFH), the recommended initial dosing is an intravenous bolus of 80 units/kg followed by a continuous infusion of 18 units/kg per hour, with dose adjustments based on aPTT monitoring to maintain a therapeutic range of 1.5-2.5 times the control value. 1
Therapeutic Anticoagulation Regimens
Intravenous Administration (Preferred for Acute Treatment)
- Initial bolus dose: 80 units/kg IV 2, 1
- Continuous infusion: 18 units/kg/hour 2, 1
- Target aPTT: 1.5-2.5 times control value (46-70 seconds for most laboratories) 1, 3
- Monitoring: Check aPTT at baseline, 4-6 hours after initiation, and then at appropriate intervals 3
Subcutaneous Administration (Alternative for Treatment)
- Initial dose: 5,000 units IV bolus, followed by 10,000-20,000 units subcutaneously 3
- Frequency: Every 8 hours or 8,000-10,000 units every 12 hours 3
- Alternative regimen: 333 units/kg initial subcutaneous dose followed by 250 units/kg twice daily 2
- Note: Subcutaneous administration has reduced bioavailability compared to IV administration 2
aPTT-Based Dose Adjustment Protocol
| aPTT (seconds) | aPTT (× control) | Action |
|---|---|---|
| <35 | <1.2 | 80 units/kg bolus; increase infusion rate by 4 units/kg/hour |
| 35-45 | 1.2-1.5 | 40 units/kg bolus; increase infusion rate by 2 units/kg/hour |
| 46-70 | 1.5-2.3 | No change (therapeutic range) |
| 71-90 | 2.3-3.0 | Reduce infusion rate by 2 units/kg/hour |
| >90 | >3.0 | Stop infusion for 1 hour, then reduce rate by 3 units/kg/hour |
| [1] |
Prophylactic Dosing for Thromboembolism
Standard Prophylaxis
- Dose: 5,000 units subcutaneously 3
- Frequency: Every 8-12 hours 1, 3
- Duration: 7 days or until fully ambulatory, whichever is longer 3
- Note: For cancer patients, every 8 hours (three times daily) is more effective 1
Special Patient Populations
Cardiovascular Surgery
- Initial dose: Not less than 150 units/kg 3
- Common dosing: 300 units/kg for procedures <60 minutes; 400 units/kg for procedures >60 minutes 3
Pediatric Patients
- Initial dose: 75-100 units/kg IV bolus over 10 minutes 3
- Maintenance dose:
- Infants: 25-30 units/kg/hour (infants <2 months have highest requirements)
- Children >1 year: 18-20 units/kg/hour
- Target aPTT: 60-85 seconds 3
Monitoring Requirements
- Baseline tests: aPTT, INR, platelet count 3
- Follow-up: aPTT approximately every 4 hours initially, then at appropriate intervals 3
- Additional monitoring: Platelet counts, hematocrit, and occult blood in stool throughout therapy 3
Clinical Considerations
Indications
- Prevention and treatment of venous thrombosis and pulmonary embolism
- Prevention of postoperative deep venous thrombosis
- Atrial fibrillation with embolization
- Treatment of acute and chronic consumptive coagulopathies
- Prevention of clotting in arterial and cardiac surgery
- Prophylaxis and treatment of peripheral arterial embolism
- Anticoagulant use in blood transfusions, extracorporeal circulation, and dialysis procedures 3
Contraindications
- History of heparin-induced thrombocytopenia (HIT)
- Known hypersensitivity to heparin or pork products
- Uncontrolled active bleeding state 3
Important Precautions
- Use preservative-free heparin in neonates and infants 3
- Administer subcutaneous injections deep (intrafat) using a fine (25-26 gauge) needle 3
- When transitioning to warfarin, continue full heparin therapy until INR reaches therapeutic range 3
- Monitor for signs of heparin-induced thrombocytopenia (HIT) 1
- Patients with severe renal impairment require more frequent monitoring 1
Dosing for Specific Clinical Scenarios
Acute Coronary Syndromes
- Unstable angina/NSTEMI: 60-70 units/kg bolus (maximum 5,000 units) followed by 12-15 units/kg/hour (maximum 1,000 units/hour) 2
- STEMI with thrombolytic therapy: 60 units/kg bolus (maximum 4,000 units) followed by 12 units/kg/hour (maximum 1,000 units/hour) 2
Extracorporeal Dialysis
- Initial dose: 25-30 units/kg
- Infusion rate: 1,500-2,000 units/hour 3
Weight-based dosing is critical for achieving therapeutic anticoagulation quickly and safely, as studies have shown higher recurrence rates with lower starting doses 2. The pharmacokinetics of heparin are complex, with both dose-dependent clearance and variable bioavailability, making careful monitoring essential for optimal outcomes 2.