What is the recommended first-line treatment for patients with acute kidney injury or severe kidney impairment requiring renal support, specifically regarding Continuous Renal Replacement Therapy (CRRT)?

Continuous Renal Replacement Therapy (CRRT) for Acute Kidney Injury

For patients with acute kidney injury requiring renal support, CRRT is recommended as first-line treatment for hemodynamically unstable patients and those with acute brain injury or increased intracranial pressure. 1, 2

Indications for CRRT

• CRRT should be initiated when metabolic and fluid demands exceed the kidney's capacity to meet them, particularly in the presence of life-threatening changes in fluid, electrolyte, and acid-base balance 1, 2
• CRRT is specifically recommended over intermittent hemodialysis for:
  • Hemodynamically unstable patients due to superior hemodynamic tolerance 1, 2
  • Patients with acute brain injury or increased intracranial pressure to minimize cerebral edema risk 1, 2
  • Patients where fluid overload cannot be adequately managed with intermittent modalities 1, 2

Technical Implementation

Vascular Access

• Use an uncuffed non-tunneled dialysis catheter of appropriate length and gauge to initiate CRRT 1
• Preferred vascular access sites (in order of preference):
  • First choice: Right jugular vein
  • Second choice: Femoral vein (less preferred in patients with increased body mass)
  • Third choice: Left jugular vein
  • Last choice: Subclavian vein 1, 2
• Always use ultrasound guidance for catheter insertion 1
• Obtain chest radiograph promptly after placement of internal jugular or subclavian catheters before first use 1

Anticoagulation

• For patients without increased bleeding risk or impaired coagulation:
  • Regional citrate anticoagulation is recommended as first choice 1, 2
  • If citrate is contraindicated, use unfractionated or low-molecular-weight heparin 1
• For patients with increased bleeding risk:
  • Consider regional citrate anticoagulation if no contraindications exist 1
  • Avoid regional heparinization 1
• For patients with heparin-induced thrombocytopenia:
  • Use direct thrombin inhibitors (argatroban) or Factor Xa inhibitors 1, 2
  • In patients without severe liver failure, argatroban is preferred 1

Dosing and Monitoring

• Deliver an effluent volume of 20-25 mL/kg/h for CRRT 1, 2, 3
• Use bicarbonate rather than lactate as buffer in dialysate and replacement fluid, especially for:
  • Patients with circulatory shock (strongly recommended)
  • Patients with liver failure and/or lactic acidemia 1, 2
• Use biocompatible membrane dialyzers 1

Modality Selection and Transition

• CRRT techniques include continuous venovenous hemofiltration (CVVH), continuous venovenous hemodialysis (CVVHD), and continuous venovenous hemodiafiltration (CVVHDF) 4
• Consider transitioning from CRRT to intermittent hemodialysis when:
  • Vasopressor support has been discontinued
  • Hemodynamic stability has been achieved
  • Intracranial hypertension has resolved
  • Fluid balance can be adequately controlled by intermittent hemodialysis 1, 2

Special Considerations

CRRT with Extracorporeal Life Support

• CRRT is particularly important in ECMO patients for preventing and managing fluid overload 1, 2
• Integration of CRRT with ECLS should be based on institutional expertise and available technology 1, 2

Recovery Assessment

• Define kidney recovery as sustained independence from RRT for at least 14 days 1
• After discontinuation of CRRT, assess kidney function within 3-7 days 1
• For patients discharged while still receiving RRT, conduct weekly assessment of pre-dialysis serum creatinine values and regular assessment of residual kidney function 1

Common Pitfalls to Avoid

• Don't rely solely on single BUN and creatinine thresholds for initiating CRRT; consider the broader clinical context 2
• Avoid using subclavian veins for access when possible due to risk of thrombosis and stenosis 1, 2
• Don't use lactate-buffered solutions in patients with liver failure or lactic acidosis 1, 2
• Avoid excessive fluid removal that could lead to hypotension and potentially delay kidney recovery 1
• Don't add medications without clear evidence of benefit, as this increases risk of adverse effects in AKI patients 5