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

Indications for Continuous Renal Replacement Therapy (CRRT)

CRRT should be initiated emergently for life-threatening complications of acute kidney injury including refractory hyperkalemia, severe metabolic acidosis, pulmonary edema unresponsive to diuretics, and uremic complications, while also considering CRRT over intermittent hemodialysis for hemodynamically unstable patients requiring vasopressor support. 1, 2

Absolute (Emergent) Indications

CRRT must be initiated immediately when the following life-threatening conditions exist 1, 2:

• Refractory hyperkalemia - medically unresponsive to conservative management 1
• Severe volume overload with pulmonary edema not responding to diuretics 1
• Severe metabolic acidosis - particularly when pH management is critical 1, 2
• Uremic complications including pericarditis or encephalopathy 1, 2

Relative Indications Based on Clinical Context

Beyond emergent scenarios, CRRT initiation should be guided by the broader clinical picture rather than single laboratory thresholds alone 1:

Hemodynamic Instability

• Patients requiring vasopressor support - CRRT provides superior hemodynamic tolerance compared to intermittent hemodialysis 1, 2
• The Surviving Sepsis Campaign guidelines specifically recommend CRRT over intermittent RRT for hemodynamically unstable septic patients 1
• Two prospective trials demonstrated better hemodynamic tolerance with continuous treatment, though without mortality benefit 1

Fluid Management Requirements

• Severe fluid overload requiring precise fluid balance control - CRRT allows for slower, more controlled fluid removal 1
• Volume overload should be avoided, especially in patients with acute lung injury, where maintaining negative fluid balance decreases ICU length of stay 1
• Two studies reported significant improvement in goal achievement with continuous methods for fluid balance management 1

Neurological Considerations

• Acute brain injury or increased intracranial pressure - CRRT carries lower risk of cerebral edema and intracranial pressure fluctuations compared to intermittent modalities 2, 3

Extracorporeal Life Support

• Patients on ECMO or ventricular assist devices - CRRT integration is critical for preventing and managing fluid overload that affects optimal ECMO function 2, 3

Metabolic Derangements

• Severe electrolyte disturbances requiring controlled correction - CRRT allows steady, predictable correction avoiding rapid shifts 4, 5
• Lactic acidosis or liver failure - particularly important as these patients require bicarbonate-buffered solutions rather than lactate 1, 2

What NOT to Use as Sole Indication

Do not initiate RRT based solely on elevated creatinine or oliguria without other definitive indications 1. The Surviving Sepsis Campaign specifically recommends against using RRT in patients with sepsis and AKI for increase in creatinine or oliguria alone, as two 2016 RCTs suggested possibility of harm including increased central line infections with early RRT 1.

Critical Pitfalls to Avoid

• Do not rely on single BUN and creatinine thresholds alone - consider trends in laboratory tests and the broader clinical context 1
• Avoid delaying CRRT in hemodynamically unstable patients while waiting for specific laboratory values 2
• Do not use subclavian veins for vascular access due to risk of thrombosis and late stenosis 1, 2
• Avoid lactate-buffered solutions in patients with liver failure or lactic acidosis - use bicarbonate instead 1, 2

Technical Implementation Once Indicated

When CRRT is initiated 2, 6:

• Vascular access: Preferred sites in order are right jugular vein, femoral vein, left jugular vein, with subclavian as last resort 2, 6
• Anticoagulation: Regional citrate anticoagulation is first-line for patients without contraindications 1, 2, 6
• Dosing: Deliver effluent volume of 20-25 mL/kg/hr 1, 2, 6
• Buffer selection: Use bicarbonate rather than lactate, especially in circulatory shock, liver failure, or lactic acidemia 2, 6, 3