Minimum Dose for Continuous Renal Replacement Therapy (CRRT)
The recommended minimum dose for CRRT is 20-25 mL/kg/h of effluent volume, which is supported by high-quality evidence and clinical practice guidelines. 1
Evidence-Based Dosing Recommendations
Minimum Effective Dose
- The KDIGO Clinical Practice Guidelines for Acute Kidney Injury strongly recommend (Level 1A evidence) delivering an effluent volume of 20-25 mL/kg/h for CRRT in acute kidney injury 1
- This recommendation is based on rigorous evidence from large randomized controlled trials:
- The RENAL study (1,508 patients) compared CVVHDF at 40 mL/kg/h vs. 25 mL/kg/h
- The ATN study (1,124 patients) compared more intensive (35 mL/kg/h) vs. less intensive (20 mL/kg/h) CRRT
- Both studies showed no added benefit in survival or kidney function recovery with higher intensity therapy 1
Prescription vs. Delivered Dose
- To account for treatment interruptions and declining filter efficiency over time, it is recommended to prescribe 25-30 mL/kg/h to ensure delivery of the target 20-25 mL/kg/h 2
- Delivered dose often falls short of prescribed dose due to:
- Treatment interruptions (circuit clotting, medical imaging, procedures)
- Declining filter efficiency over time
- Studies show delivered dose may be only 68-85% of prescribed dose 1
Clinical Implementation
Monitoring and Adjustment
- The dose of CRRT should be prescribed before starting each session 1
- Frequent assessment of the actual delivered dose is essential to adjust the prescription (Level 1B recommendation) 1
- Quality improvement initiatives that include real-time calculation of delivered dose in electronic medical records can significantly improve adherence to dosing guidelines 3
Special Considerations
- For intermittent hemodialysis in AKI, the recommended minimum is a Kt/V of 3.9 per week (Level 1A recommendation) 1
- While the minimum dose is 20-25 mL/kg/h, transient higher doses may be needed for specific clinical scenarios requiring enhanced solute control 2
- Higher doses may increase the risk of undesired clearance of antimicrobials and nutrients 2
Common Pitfalls and Caveats
- Failing to account for the gap between prescribed and delivered dose
- Not adjusting for patient weight changes in the ICU
- Inconsistent documentation of actual delivered dose
- Relying solely on prescribed dose without monitoring actual delivered dose
- Assuming that higher doses are always better (studies show no benefit beyond the recommended range)
The 20-25 mL/kg/h recommendation represents a balance between ensuring adequate solute clearance while avoiding unnecessary costs and potential complications associated with higher intensity therapy. Adherence to this evidence-based minimum dose is essential for optimal patient outcomes in acute kidney injury requiring CRRT.