How does the modality effect solute clearance?

Size
Examples
Removal
Small Molecules
<500 Da
  • Urea
  • Creatinine
  • Potassium
  • Oxalate
  • Uric acid
  • Better cleared by diffusion (Haemodialysis)
  • Rate of clearance increased by:
    • Increasing speed of dialysis fluid flow
Middle Molecules
500 - 60,000 Da
Albumin is 66 kDa (Not a middle molecule!)
  • Interleukins
  • Cytokines
  • B2 -microglobulin
  • ANP
  • TNF
  • Light chains
  • Better cleared by convection (Hemofiltration)
  • Dialysis clearance increased by:
    • Increased dialysis time
    • Increased membrane pore size
    • Increased membrane surface area
Protein-Bound Molecules
Variable
  • Homocysteine
  • Hippuric acid
  • Phenol
  • Difficult to remove via RRT
  • Clearance improved by:
    • Increased time and flow
    • Absorbent technology
    • Albumin dialysis