What are the indications for Continuous Renal Replacement Therapy (CRRT)?

Indications for Continuous Renal Replacement Therapy (CRRT)

CRRT is indicated for hemodynamically unstable patients with acute kidney injury who cannot tolerate intermittent hemodialysis, patients with acute brain injury or increased intracranial pressure, and patients requiring continuous fluid removal or management of severe volume overload. 1, 2

Absolute Indications for Emergent Dialysis

• Life-threatening changes in fluid, electrolyte, and acid-base balance require immediate initiation of CRRT 1
• Severe hyperkalemia or rapidly rising potassium levels with ECG changes 1
• Severe metabolic acidosis with impaired compensation 1
• Pulmonary edema or severe fluid overload causing respiratory compromise 1
• Uremic complications including encephalopathy, pericarditis, and bleeding 1

Patient-Specific Indications for CRRT over Intermittent Hemodialysis

• Hemodynamic instability requiring vasopressor support 3, 4
• Acute brain injury or increased intracranial pressure 3, 4
• Severe fluid overload unresponsive to diuretics 1, 4
• Patients on extracorporeal life support (ECLS) such as ECMO 4
• Patients with septic shock who may benefit from continuous removal of inflammatory mediators 2

CRRT Modality Selection

• Continuous Venovenous Hemofiltration (CVVH) uses primarily convective clearance and is suitable for patients requiring efficient cytokine removal 2
• Continuous Venovenous Hemodialysis (CVVHD) uses primarily diffusive clearance and is appropriate for patients requiring efficient small solute removal 2
• Continuous Venovenous Hemodiafiltration (CVVHDF) combines both convective and diffusive clearance methods and is recommended as the primary modality for most critically ill patients 2, 4

Technical Aspects of CRRT Implementation

Vascular Access

• The preferred vein selection order is: right jugular vein (first choice), femoral vein (second choice), left jugular vein (third choice), and subclavian vein (last choice) 3, 4
• Ultrasound guidance should always be used for catheter insertion 3, 2
• Chest radiograph is required after placement and before first use of internal jugular or subclavian catheters 3, 2

Anticoagulation

• Regional citrate anticoagulation is recommended for patients without contraindications 3, 2
• For patients with heparin-induced thrombocytopenia (HIT), direct thrombin inhibitors (such as argatroban) or Factor Xa inhibitors should be used 3, 2

Dosing and Monitoring

• The recommended effluent volume for CRRT in AKI is 20-25 mL/kg/h 3, 4
• Bicarbonate is preferred over lactate as buffer in dialysate and replacement fluid, especially for patients with circulatory shock, liver failure, or lactic acidemia 3, 2
• The actual delivered dose should be frequently assessed and prescription adjusted accordingly 3, 2

Common Pitfalls and Considerations

• Avoid using subclavian veins for access due to risk of thrombosis and late stenosis 2, 4
• Don't rely solely on BUN and creatinine thresholds for initiating RRT; consider the broader clinical context 2
• Avoid using lactate-buffered solutions in patients with liver failure or lactic acidosis 3, 2
• Recognize that excessive ultrafiltration rates can lead to hemodynamic instability even with CRRT 2
• Be aware that the optimal timing for initiation of RRT remains uncertain and requires clinical judgment 3

Transitioning from CRRT to Intermittent Modalities

• Consider transitioning from CRRT to intermittent hemodialysis when vasopressor support has been discontinued, hemodynamic stability has been achieved, intracranial hypertension has resolved, and fluid balance can be adequately controlled by intermittent hemodialysis 1
• The selection of RRT modality does not appear to have a major impact on recovery of kidney function 4

Evidence on CRRT Intensity

• Current evidence does not support higher intensity CRRT (>35 mL/kg/h) over standard intensity (20-25 mL/kg/h) for improving mortality or kidney recovery in most patients with AKI 5
• However, post-surgical AKI patients may benefit from more intensive CRRT regimens 5

CRRT remains the preferred modality for critically ill patients with AKI who are hemodynamically unstable, providing advantages in fluid management, hemodynamic stability, and solute control compared to intermittent hemodialysis 6, 7.