Chart — Critical Care
CRRT Modality Comparison
CVVH vs. CVVHD vs. CVVHDF — mechanism, fluid requirements, clearance profile, and clinical use cases for each CRRT modality.
Educational use only. CRRT prescriptions, anticoagulation, and circuit management are provider- and protocol-driven; this comparison supports concept review only. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
CVVH
Convection Only
Fluid + solutes pushed across membrane under pressure. Requires replacement fluid. Best for middle-molecule and cytokine clearance.
CVVHD
Diffusion Only
Solutes move from high-concentration blood to low-concentration dialysate. No replacement fluid. Best for uremia and hyperkalemia.
CVVHDF
Convection + Diffusion
Combines both mechanisms. Uses both dialysate and replacement fluid. Broadest clearance spectrum. Most common ICU modality.
Feature-by-Feature Comparison
| Feature | CVVH | CVVHD | CVVHDF |
|---|---|---|---|
| Full Name | Continuous Veno-Venous Hemofiltration | Continuous Veno-Venous Hemodialysis | Continuous Veno-Venous Hemodiafiltration |
| Primary Mechanism | Convection (solvent drag) | Diffusion (concentration gradient) | Convection + Diffusion (both) |
| Dialysate Used | No | Yes — countercurrent flow | Yes |
| Replacement Fluid Used | Yes — required to replace UF volume | No | Yes |
| Small Molecule Clearance (urea, creatinine, K+) | Moderate | High (excellent) | High |
| Middle Molecule Clearance (cytokines, larger solutes) | High (excellent) | Low | High |
| Fluid Removal Capability | High (UF is primary mechanism) | Moderate (diffusion-driven) | High |
| Fluid Management Complexity | Moderate (one fluid: replacement) | Moderate (one fluid: dialysate) | High (two fluids: both) |
| Filter Life | Standard (clotting risk with post-dilution) | Standard | Standard (pre-dilution reduces clot risk) |
| Best For | Fluid overload; cytokine clearance in sepsis | Pure uremia; refractory hyperkalemia | General ICU AKI — most common modality |
| Complexity | Moderate | Moderate | Highest (but broadest clearance) |
Pre-Dilution vs. Post-Dilution (CVVH/CVVHDF)
| Method | Replacement Fluid Added | Effect on Clearance | Effect on Clotting |
|---|---|---|---|
| Pre-dilution | Before the filter (upstream) | Reduced (dilutes blood before filtration) | Reduced (diluted blood is less viscous) |
| Post-dilution | After the filter (downstream) | Maximized (undiluted blood filtered) | Increased risk (concentrated blood in filter) |
Key Pearls
- ›CVVHDF is the most common ICU modality — it combines convection and diffusion for the broadest clearance.
- ›CVVH clears middle molecules (cytokines) better than CVVHD — relevant in cytokine storm or sepsis.
- ›CVVHD is the best choice for pure uremia and refractory hyperkalemia without fluid issues.
- ›Post-dilution replacement fluid improves clearance but increases filter clotting risk; pre-dilution is safer for anticoagulation-limited patients.
- ›All CRRT modalities remove electrolytes — monitor K+, PO4, Mg2+ every 4–6 hours.
- ›CRRT causes hypothermia — actively warm patients and monitor temperature.
Standards & sources
Fact-checked Jun 20, 2026This page is written to align with Society of Critical Care Medicine (SCCM) · Surviving Sepsis Campaign · American Association of Critical-Care Nurses (AACN). It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →