What are the recommended types of Continuous Renal Replacement Therapy (CRRT) for patients with acute kidney injury?

Recommended Types of Continuous Renal Replacement Therapy (CRRT) for Acute Kidney Injury

For patients with acute kidney injury requiring renal replacement therapy, continuous venovenous hemodiafiltration (CVVHDF) is recommended as the primary CRRT modality, particularly for hemodynamically unstable patients, while modality selection should be tailored based on the patient's clinical condition, institutional expertise, and available resources. 1, 2

CRRT Modality Options

• Continuous Venovenous Hemofiltration (CVVH): Uses convective clearance where the effluent rate refers to the ultrafiltration rate 2
• Continuous Venovenous Hemodialysis (CVVHD): Uses diffusive clearance where the effluent rate refers to the dialysate flow rate 2
• Continuous Venovenous Hemodiafiltration (CVVHDF): Combines both diffusive and convective clearance, where the effluent rate is the sum of dialysate and ultrafiltration rates 2

Patient-Specific CRRT Modality Selection

Recommended for CVVHDF or CVVH:

• Hemodynamically unstable patients requiring vasopressor support 1, 3
• Patients with acute brain injury or increased intracranial pressure 3, 4
• Patients with severe fluid overload that cannot be managed with intermittent modalities 1, 3
• Patients on extracorporeal life support (ECLS) such as ECMO 1, 3

Technical Considerations:

• For all CRRT modalities, deliver an effluent volume of 20-25 mL/kg/h 1, 2
• Use bicarbonate-based replacement fluids rather than lactate-based solutions, especially in patients with shock, liver failure, or lactic acidemia 2, 4
• Regional citrate anticoagulation is recommended for patients without contraindications 1, 4

Vascular Access for CRRT

• First choice: Right jugular vein or femoral vein (note: femoral site is inferior in patients with increased body mass) 1, 4
• Second choice: Left jugular vein 1, 4
• Last resort: Subclavian vein (avoid due to risk of thrombosis and stenosis) 1, 4
• Always use ultrasound guidance for catheter insertion 4

Dosing Recommendations

• Deliver an effluent volume of 20-25 mL/kg/h for all CRRT modalities 1, 2
• The prescribed dose should be higher than the target delivered dose to account for treatment interruptions 2
• Regularly assess the actual delivered dose to ensure adequate therapy 2, 4

Transitioning Between Modalities

• Consider transitioning from CRRT to intermittent hemodialysis when: 1, 3
  • Vasopressor support has been discontinued
  • Hemodynamic stability has been achieved
  • Intracranial hypertension has resolved
  • Positive fluid balance can be adequately controlled by intermittent hemodialysis

Common Pitfalls to Avoid

• Don't rely solely on BUN and creatinine thresholds for initiating CRRT; consider the broader clinical context 3, 4
• Avoid using subclavian veins for access due to risk of thrombosis and stenosis 3, 4
• Don't use lactate-buffered solutions in patients with liver failure or lactic acidosis 3, 4
• Avoid volume overload, especially in patients with acute lung injury 4

Special Considerations

• For patients requiring ECMO or other extracorporeal life support, CRRT is particularly important for preventing and managing fluid overload 1, 3
• The selection of RRT modality does not appear to have a major impact on recovery of kidney function 1
• Low-dose CRRT (around 16 mL/kg/h) may be effective and not increase mortality in critically ill patients with AKI 5