What is the difference between Continuous Renal Replacement Therapy (CRRT) and Peritoneal Irrigation and Renal Replacement Therapy (PIRRT)?

Differences Between CRRT and PIRRT

Continuous Renal Replacement Therapy (CRRT) and Prolonged Intermittent Renal Replacement Therapy (PIRRT) differ primarily in their duration of application, with CRRT running continuously for 24 hours per day while PIRRT operates for shorter periods (typically 6-12 hours) with planned interruptions.

Key Differences

Duration of Treatment

• CRRT: Applied continuously for 24 hours per day 1
• PIRRT: Applied for shorter periods (6-12 hours), with planned interruptions 1

Hemodynamic Stability

• CRRT: Preferred for hemodynamically unstable patients due to slower solute and fluid removal rates 1
• PIRRT: Can be used in hemodynamically unstable adult patients but with less evidence supporting its use 1

Solute Clearance

• CRRT: Provides slower, more continuous solute clearance, resulting in less dramatic shifts in electrolytes and fluid balance 2
• PIRRT: Achieves higher solute clearance rates during the treatment period but with potential for more rapid shifts 1

Clinical Applications

CRRT is particularly recommended for:

1. Hemodynamically unstable patients 1
2. Patients with acute brain injury or increased intracranial pressure 1
3. Management of fluid balance in critically ill patients 1

PIRRT considerations:

1. Reasonable alternative to CRRT in hemodynamically unstable adult patients 1
2. May be more cost-effective due to reduced staffing requirements and dialysate usage 1
3. Limited evidence in pediatric populations 1

Technical Aspects

CRRT Modalities

• Continuous venovenous hemofiltration (CVVH): Primarily convective clearance
• Continuous venovenous hemodialysis (CVVHD): Primarily diffusive clearance
• Continuous venovenous hemodiafiltration (CVVHDF): Combines both convective and diffusive clearance 1

Dosing Considerations

• CRRT: Typically requires an effluent volume of 20-25 mL/kg/h 1
• PIRRT: Dosing is less standardized but aims to achieve similar weekly clearance as CRRT 1

Clinical Decision-Making

When choosing between CRRT and PIRRT, consider:

1. Hemodynamic status: CRRT is preferred for severely unstable patients 1
2. Neurological status: CRRT is recommended for patients with brain injury or increased intracranial pressure 1
3. Resource availability: PIRRT may be more feasible in settings with limited resources 1
4. Patient mobility needs: PIRRT allows for periods off dialysis for procedures or rehabilitation

Potential Pitfalls

1. Filter clotting: More common in CRRT due to longer circuit exposure time
2. Anticoagulation management: Critical for CRRT success; requires careful monitoring
3. Fluid balance errors: Can occur with both modalities but require particular attention with CRRT due to continuous nature
4. Medication dosing: Requires adjustment for both modalities but is more complex with CRRT due to continuous clearance

Research Gaps

The KDOQI Work Group notes that additional research is needed to compare outcomes between PIRRT and other RRT modalities 1. Recent research suggests that CRRT may not offer survival benefits over intermittent modalities and might even be associated with less favorable outcomes in less severely ill patients 3.