What is the difference between emergent temporary dialysis and Continuous Renal Replacement Therapy (CRRT)?

Differences Between Emergent Temporary Dialysis and CRRT

Emergent temporary dialysis (intermittent hemodialysis) and Continuous Renal Replacement Therapy (CRRT) are distinct modalities with different applications, with CRRT being preferred for hemodynamically unstable patients while intermittent hemodialysis is better suited for stable patients requiring rapid correction of life-threatening conditions. 1

Key Differences

1. Duration and Continuity

• Intermittent Hemodialysis (IHD):

  • Short, intensive sessions (typically 3-4 hours)
  • Performed intermittently (usually daily in acute settings)
  • Higher blood and dialysate flow rates

• CRRT:

  • Continuous therapy (24 hours/day)
  • Slower blood flow rates
  • Gradual solute removal and fluid correction 1

2. Hemodynamic Stability

• IHD:

  • More likely to cause hemodynamic instability
  • Rapid fluid and solute shifts
  • Less suitable for patients with cardiovascular instability

• CRRT:

  • Better hemodynamic tolerance in unstable patients
  • Slower, more physiologic fluid and solute removal
  • Recommended for hemodynamically unstable patients 1

3. Clinical Indications

Preferred Use of CRRT:

• Hemodynamically unstable patients 1
• Patients with or at risk for cerebral edema 1
• Patients with acute brain injury 1
• Severe fluid overload requiring gradual correction 1
• Septic patients requiring careful fluid management 1

Preferred Use of IHD:

• Hemodynamically stable patients
• Need for rapid correction of life-threatening electrolyte abnormalities
• Acute poisoning requiring rapid toxin removal
• Patients without risk of cerebral edema 1

4. Solute Clearance and Fluid Management

• IHD:

  • Higher efficiency for rapid solute removal
  • Less precise volume control
  • Better for rapid correction of severe hyperkalemia or toxin removal

• CRRT:

  • More precise control of fluid balance
  • Steady correction of electrolyte disturbances
  • Better for management of fluid overload in critically ill patients 2

5. Technical Aspects

• IHD:

  • Requires specialized dialysis staff
  • Higher blood flow rates (200-400 mL/min)
  • Higher dialysate flow rates

• CRRT:

  • Can be managed by ICU staff with appropriate training
  • Lower blood flow rates (100-200 mL/min)
  • Uses replacement fluid and/or dialysate at slower rates
  • Requires continuous anticoagulation (preferably regional citrate) 1, 3

Practical Considerations

Dosing

• IHD: Recommended Kt/V of 3.9 per week 1
• CRRT: Recommended effluent volume of 20-25 mL/kg/h 1

Anticoagulation

• CRRT: Regional citrate anticoagulation is preferred unless contraindicated 1
• IHD: Unfractionated or low-molecular-weight heparin is commonly used 1

Clinical Decision Algorithm

1. Assess hemodynamic stability:

   • If unstable (requiring vasopressors, MAP fluctuations): Choose CRRT
   • If stable: Consider IHD

2. Evaluate neurological status:

   • If cerebral edema or increased intracranial pressure: Choose CRRT
   • If neurologically stable: Either modality appropriate

3. Consider urgency of correction:

   • If life-threatening hyperkalemia/acidosis requiring immediate correction: Consider IHD
   • If gradual correction preferred: Choose CRRT

4. Assess fluid status:

   • If severe fluid overload with hemodynamic compromise: CRRT offers better control
   • If euvolemic or mild overload: Either modality appropriate

Common Pitfalls to Avoid

1. Using IHD in hemodynamically unstable patients, which may worsen hypotension
2. Selecting CRRT when rapid correction of life-threatening electrolyte abnormalities is needed
3. Failing to provide adequate anticoagulation during CRRT, leading to frequent circuit clotting
4. Underestimating the risk of electrolyte disturbances (particularly hypophosphatemia, hypokalemia) during prolonged CRRT 2
5. Delaying initiation of RRT when life-threatening indications exist 1

Despite theoretical advantages of CRRT in certain populations, recent evidence suggests no clear mortality benefit of one modality over the other 4, emphasizing that the choice should be guided by the patient's specific clinical condition rather than assumed superiority of either technique.