What are the guidelines for Renal Replacement Therapy (RRT) in patients on Extracorporeal Membrane Oxygenation (ECMO)?

Guidelines for Renal Replacement Therapy in ECMO Patients

Continuous renal replacement therapy (CRRT) is the preferred modality for patients on ECMO due to their hemodynamic instability and heightened sensitivity to fluid overload. 1

Indications for RRT in ECMO Patients

The indications for initiating RRT in ECMO patients are similar to standard indications but with greater emphasis on fluid management:

• Primary indications:

  • Persistent anuria/oliguria
  • Metabolic acidosis
  • Fluid overload (particularly important in ECMO patients)
  • Hyperkalemia 2

• Special consideration: Earlier RRT initiation may be required in ECMO patients specifically for preventing and managing fluid overload, as these patients are particularly sensitive to volume status issues 1

RRT Modality Selection

• CRRT is strongly recommended over intermittent hemodialysis for ECMO patients due to:

  • Better hemodynamic stability
  • More effective management of fluid balance
  • Reduced risk of cerebral edema 1

• Continuous veno-venous hemofiltration (CVVH) is the most commonly used CRRT technique (64% of centers), followed by continuous veno-venous hemodiafiltration (CVVHDF) (21% of centers) 2

Circuit Configuration Options

Two main approaches exist for connecting RRT to ECMO:

1. Integrated approach (40% of centers):

   • RRT device connected directly into the ECMO circuit
   • Most commonly connected with inlet and outlet lines after the ECMO pump (58%)
   • May experience pressure alarms (reported by 60% of users) 2

2. Parallel system (30% of centers):

   • Separate ECMO and RRT circuits
   • Requires additional vascular access 2, 3

Anticoagulation Management

• Unfractionated heparin is the first-line choice for anticoagulation (61% of centers) 2

• Regional citrate anticoagulation is used in 16% of centers and should be considered when not contraindicated 2, 1

• For patients with heparin-induced thrombocytopenia (HIT):

  • Stop all heparin immediately
  • Use direct thrombin inhibitors (argatroban) or Factor Xa inhibitors (danaparoid, fondaparinux) 1
  • Argatroban is preferred in patients without severe liver failure 1

Vascular Access for RRT

• Catheter placement preferences:

  1. First choice: Right jugular vein
  2. Second choice: Femoral vein
  3. Third choice: Left jugular vein
  4. Last choice: Subclavian vein 1

• Always use ultrasound guidance for dialysis catheter insertion 1

• Obtain chest radiograph promptly after placement of jugular or subclavian catheters 1

RRT Dosing and Management

• Effluent volume: Deliver 20-25 mL/kg/h for CRRT 1

  • Note: Higher prescription may be needed to achieve target delivery

• For intermittent RRT: Deliver a Kt/V of 3.9 per week 1

• Buffer solution: Use bicarbonate rather than lactate as buffer in dialysate and replacement fluid 1

Monitoring and Outcomes

• Fluid balance is a critical parameter - patients with positive fluid balance at 72 hours have significantly higher mortality 4

• Regular monitoring needed:

  • Electrolytes
  • Acid-base status
  • Fluid balance
  • Circuit pressures 5

• Mortality considerations:

  • Combined ECMO/CRRT is associated with 63% pooled mortality 6
  • Mortality has decreased by 20% in recent years 6
  • Positive fluid balance and increased age are independently associated with mortality 4

Practical Considerations

• Assess for pressure alarms when using integrated circuit approaches 2

• Dialysis fluids and replacement fluids should comply with American Association of Medical Instrumentation (AAMI) standards regarding bacterial and endotoxin contamination 1

• Biocompatible membranes should be used for dialyzers 1

• Multidisciplinary approach involving intensivists, nephrologists, and ECMO specialists is essential for optimal management 1

Pitfalls to Avoid

• Delaying RRT initiation in fluid-overloaded ECMO patients can worsen outcomes
• Inadequate anticoagulation monitoring can lead to circuit clotting or bleeding complications
• Improper circuit integration may cause pressure alarms and ineffective therapy
• Failure to adjust fluid removal goals based on hemodynamic status can lead to instability
• Not accounting for drug dosing adjustments when using combined ECMO and CRRT

The management of RRT in ECMO patients requires specialized knowledge of both systems and careful attention to the unique challenges presented by this complex patient population.