Heparin Dosing for CRRT
The typical starting dose of heparin for patients undergoing Continuous Renal Replacement Therapy (CRRT) is 25 to 30 units/kg as an initial bolus followed by an infusion rate of 1,500 to 2,000 units/hour, with dose adjustments based on activated partial thromboplastin time (aPTT) monitoring. 1
Standard Heparin Dosing Protocol for CRRT
- Initial bolus: 25-30 units/kg intravenously 1
- Maintenance infusion: 1,500-2,000 units/hour 1
- Target aPTT: 1.5-2.0 times the patient's baseline (typically 45-75 seconds) 2, 1
- Monitor aPTT every 4 hours initially, then at appropriate intervals after achieving steady state 1
Dose Adjustment Considerations
- Adjust heparin dose based on aPTT results to maintain the target range of 1.5-2.0 times baseline 2, 1
- For patients with renal insufficiency, standard heparin is preferred over low molecular weight heparins as it does not require dose adjustment for renal function (metabolism is primarily hepatic) 3
- In patients with high bleeding risk, consider lower initial doses with careful monitoring 2
Alternative Anticoagulation Options for CRRT
For patients with contraindications to heparin (such as heparin-induced thrombocytopenia):
- Argatroban: No initial bolus, starting infusion rate of 0.5-1.2 μg/kg/min for patients with heart failure, multiple organ failure, or severe anasarca; target aPTT 1.5-3 times baseline 2
- Bivalirudin: No initial bolus, starting infusion rate of 0.15-0.20 mg/kg/h; target aPTT 1.5-2.5 times baseline 2
- Regional citrate anticoagulation: Starting dose of 2.0-2.6 mmol/L, which may provide longer filter life (46.94h vs 40.05h for heparin) with potentially fewer bleeding complications 4
Monitoring and Safety
- Regular monitoring of aPTT is essential to prevent both clotting of the circuit and bleeding complications 1
- Monitor platelet counts, hematocrit, and check for occult blood in stool throughout therapy 1
- Filter survival with heparin averages 26-31 hours, which may be slightly shorter than with citrate but longer than with intermittent hirudin 5, 4, 6
Common Pitfalls to Avoid
- Using fixed-dose regimens rather than weight-based dosing can lead to subtherapeutic anticoagulation 7
- Failure to achieve therapeutic aPTT within 24 hours is associated with reduced filter life and efficacy 7
- Inadequate monitoring of aPTT can lead to either circuit clotting or excessive bleeding 7, 8
- In patients with baseline prolonged aPTT (>55 seconds), consider saline flushes instead of heparin to reduce bleeding risk 8
Special Considerations
- For patients with heparin-induced thrombocytopenia (HIT), argatroban is preferred due to its hepatic clearance, especially in the setting of renal insufficiency 2
- Early achievement of therapeutic aPTT is associated with better outcomes and filter survival 7
- Some centers use regional anticoagulation techniques (citrate) which may provide longer filter life with fewer systemic bleeding complications 4, 6