Differences Between CRRT, Plasma Exchange, and Peritoneal Dialysis
Continuous Renal Replacement Therapy (CRRT) is the preferred modality for hemodynamically unstable patients with acute kidney injury, while peritoneal dialysis is better suited for stable patients requiring long-term therapy, and plasma exchange is specifically used for removing pathologic substances from plasma. 1
Continuous Renal Replacement Therapy (CRRT)
Key Characteristics
- Extracorporeal therapy that provides continuous blood purification over 24 hours
- Vascular access required via central venous catheter (preferably right internal jugular vein)
- Hemodynamic stability is a major advantage in critically ill patients
- Modalities include: CVVH (hemofiltration), CVVHD (hemodialysis), CVVHDF (hemodiafiltration)
Indications
- Hemodynamically unstable patients with AKI
- Patients with acute brain injury or increased intracranial pressure
- Management of fluid overload in critically ill patients
- Severe metabolic derangements requiring continuous correction
Advantages
- Better hemodynamic tolerance in unstable patients
- Superior fluid balance management
- Gradual solute removal prevents rapid shifts
- Continuous therapy allows for better nutritional support
- Avoids rapid fluid and electrolyte shifts that may worsen brain edema 1
Limitations
- Requires specialized equipment and trained staff
- Needs continuous anticoagulation (citrate or heparin)
- Higher cost compared to intermittent therapies
- Risk of catheter-related complications
- Requires immobilization of patient
Peritoneal Dialysis (PD)
Key Characteristics
- Intracorporeal therapy using the peritoneum as a semipermeable membrane
- Abdominal access via peritoneal catheter
- Utilizes the patient's own peritoneum as the dialysis membrane
- Relies on diffusion, osmosis, and convection across the peritoneal membrane
Indications
- Chronic kidney disease requiring dialysis
- Stable patients with acute kidney injury (less common)
- Patients with difficult vascular access
- Home-based renal replacement therapy
Advantages
- Does not require vascular access
- Can be performed at home
- Better preservation of residual renal function
- Lower risk of hemodynamic instability
- Lower cost compared to CRRT
- Does not require anticoagulation
Limitations
- Lower efficiency in solute removal compared to CRRT and hemodialysis
- Limited usefulness in patients requiring significant solute removal
- Risk of peritonitis
- Contraindicated in patients with recent abdominal surgery or peritonitis
- Less effective for rapid correction of severe metabolic derangements 1, 2, 3
Plasma Exchange (Plasmapheresis)
Key Characteristics
- Extracorporeal therapy that separates plasma from blood cells
- Removes pathologic substances from plasma
- Replaces removed plasma with fresh frozen plasma or albumin
- Vascular access required (similar to CRRT)
Indications
- Autoimmune disorders (e.g., Guillain-Barré syndrome)
- Thrombotic thrombocytopenic purpura
- Antibody-mediated rejection in transplantation
- Certain toxin ingestions
- Tumor lysis syndrome (in specific cases)
Advantages
- Effective removal of large molecular weight substances (antibodies, immune complexes)
- Rapid removal of pathologic substances from circulation
- Can be combined with other extracorporeal therapies
Limitations
- Risk of allergic reactions to replacement fluids
- Coagulation abnormalities
- Hypocalcemia (when using citrate anticoagulation)
- Removal of beneficial substances (medications, clotting factors)
- Requires specialized equipment and expertise 1
Key Technical Differences
| Feature | CRRT | Peritoneal Dialysis | Plasma Exchange |
|---|---|---|---|
| Mechanism | Extracorporeal blood filtration | Peritoneal membrane diffusion | Plasma separation and replacement |
| Access | Central venous catheter | Peritoneal catheter | Central venous catheter |
| Efficiency | Moderate to high | Low to moderate | High for specific substances |
| Hemodynamic impact | Minimal | Minimal | Moderate |
| Anticoagulation | Required (citrate or heparin) | Not required | Required |
| Setting | ICU | Hospital or home | Hospital |
| Cost | High | Low | Very high |
| Solute clearance | 20-25 mL/kg/hr effluent | Lower than CRRT | Variable based on plasma volume |
Clinical Decision Algorithm
For hemodynamically unstable patients with AKI:
- Choose CRRT (preferably CVVHDF)
- Target effluent dose of 20-25 mL/kg/hr
- Use regional citrate anticoagulation if available
For stable patients with chronic kidney disease:
- Consider peritoneal dialysis
- Evaluate for home therapy potential
- Monitor for peritonitis risk
For patients with specific pathologic substances to remove:
- Consider plasma exchange
- Determine appropriate replacement fluid
- Monitor for allergic reactions and coagulation abnormalities
For patients with tumor lysis syndrome:
- CRRT is preferred for hemodynamically unstable patients
- Intermittent hemodialysis may be used for stable patients
- Peritoneal dialysis is seldom used due to lower efficiency 1
Remember that the choice of renal replacement modality should be based on the patient's clinical condition, the specific goals of therapy, and the available resources and expertise at your institution.