Unfractionated Heparin Anticoagulation for CRRT When Circuit Clotting Occurs
Unfractionated heparin anticoagulation during CRRT is commonly delivered as a prefilter infusion with a loading bolus followed by titration to aPTT targets based on bleeding risk [1].
Medication Selection Algorithm
- Unfractionated heparin (prefilter bolus plus prefilter infusion) is used when citrate is contraindicated or unavailable, with dose adjustment based on circuit anticoagulation and bleeding risk [1].
Key Evidence Supporting This Recommendation
- In a prospective randomized trial of CRRT anticoagulation with unfractionated heparin, heparin was started with a bolus of 2000–5000 U followed by an infusion of 10 U/kg/hour, titrated to an aPTT target of 70–80 seconds [1].
- In a second CRRT trial in a crossover design, unfractionated heparin was given as a bolus of 30 U/kg followed by an infusion of 7 U/kg/hour, titrated to an aPTT target of 40–45 seconds [1].
- In a third trial, unfractionated heparin was administered as a bolus of 3000–5000 U followed by an infusion of 1500 U/hour, adjusted to an aPTT target of 50–70 seconds [1].
Monotherapy Versus Combination Therapy
- Unfractionated heparin anticoagulation for CRRT is typically used as heparin-only anticoagulation with laboratory titration rather than fixed dosing, because the relationship between heparin dose, aPTT, filter survival, and bleeding risk is not straightforward [1].
Important Clarifications or Nuances
- Unfractionated heparin prefilter dosing strategies show large variability across protocols, so dose selection should be coupled to aPTT monitoring and bleeding-risk adjustment [1].
- One published CRRT heparin protocol development suggested use of a relatively small bolus approach (example: 2500 IU heparin bolus on connection) when replacing a larger prime-bolus strategy [2].
Initiation Thresholds or Indications
When circuit clotting occurs, the anticoagulation regimen should be escalated to achieve the chosen heparin monitoring target (commonly an aPTT target) using one of the trial-supported starting strategies below [1].
- Strategy A (trial-supported): bolus 2000–5000 U prefilter with infusion 10 U/kg/hour, titrate to aPTT 70–80 seconds [1].
- Strategy B (trial-supported): bolus 30 U/kg prefilter with infusion 7 U/kg/hour, titrate to aPTT 40–45 seconds [1].
- Strategy C (trial-supported): bolus 3000–5000 U prefilter with infusion 1500 U/hour, adjust to aPTT 50–70 seconds [1].
Common Pitfalls to Avoid
- Fixed heparin infusion rates without titration to an anticoagulation effect target can lead to inadequate circuit anticoagulation or excess bleeding risk due to variable dose–aPTT–outcome relationships [1].
Target Blood Pressure
- Blood pressure targets are not a determinant of unfractionated heparin dosing for CRRT anticoagulation in guideline-based dosing strategies [1].
Prefilter Unfractionated Heparin Dose Used for a Clotting CRRT Circuit (Practical Dosing Range)
A commonly used trial-supported escalation approach for prefilter unfractionated heparin when the CRRT circuit is clotting is:
- Loading bolus: 2000–5000 U prefilter [1].
- Initial infusion: 10 U/kg/hour prefilter, with titration to an aPTT target of 70–80 seconds [1].
If an alternate aPTT target is used by local practice, trial-supported alternatives include:
- 30 U/kg bolus plus 7 U/kg/hour infusion titrated to aPTT 40–45 seconds [1].
- 3000–5000 U bolus plus 1500 U/hour infusion adjusted to aPTT 50–70 seconds [1].