RRT Modalities  

Continuous Renal Replacement Therapy (CRRT) 

1. CVVH – Continuous Veno-Venous Hemofiltration 
Primary mechanism: Convection 
Solute removal: Solvent drag (good for middle molecules) 
Replacement fluid: Required 
Given pre-filter, post-filter, or both 
Dialysate: ❌ None 
Best for: Hemodynamically unstable patients; better cytokine/middle-molecule clearance 

2. CVVHD – Continuous Veno-Venous Hemodialysis 
Primary mechanism: Diffusion 
Solute removal: Small molecules (urea, creatinine, K⁺) 
Dialysate: ✅ Required 
Replacement fluid: ❌ Not used 
Best for: Efficient small-solute clearance with stable fluid balance 

3. CVVHDF – Continuous Veno-Venous Hemodiafiltration 
Primary mechanism: Diffusion + Convection 
Solute removal: Small + middle molecules (most comprehensive) 
Dialysate: ✅ Yes 
Replacement fluid: ✅ Yes 
Best for: Maximal solute clearance (most commonly used CRRT mode in many ICUs) 

Prolonged Intermittent Therapy 

4. SLEDD – Sustained Low-Efficiency Daily Dialysis 
Type: Hybrid (between CRRT & intermittent HD) 
Duration: ~6–12 hours 
Mechanism: Mostly diffusion 
Hemodynamic stability: Better than IHD, not as gentle as CRRT 
Anticoagulation: Often not required 
Best for: ICUs without CRRT or patients transitioning off CRRT 

Quick Comparison Table 

Mnemonic & Quick Guide 
Easy Mnemonic 
H = Hemofiltration = Convection 
D = Dialysis = Diffusion 
F = Filtration (both) 
 
So remember: 
• CVVH → H → Convection only 
• CVVHD → D → Diffusion only 
• CVVHDF → H + D → Both convection & diffusion 
• SLEDD → Slow Dialysis (hybrid, diffusion-based) 
Ultra‑Short Memory Trick 
VHD → Dialysis (Diffusion) 
VH → Hemofiltration (Convection) 
VHDF → Everything 

Comparison Table