Hd Physiology

HAEMODIALYSIS Arwedi Arwanto

Evolution of Renal Replacement Therapy Kramer, 1977 First CRRT (CAVH)

 Abel, 1913

Kolff, 1945

1994  Automated CRRT

CRRT or SLEDD?

Teschan, 1950s

Since 1960s Daily dialysis? First dialysis First dialysis Daily dialysis in of animal in human Korean war  Chronic, intermittent hemodialysis (IHD) ( 24hrs q.w. 10-16hrs b.i.w. 4-6hrs t.i.w. )

Basic Principle of Renal Replacement Therapy

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HD is term used to describe the process whereby the solute composition of blood is altered by its contact with another solution through a semipermeable membrane HD remove solute from the blood by 2 processes: - diffusion (movement of a solute across the membrane down a concentration gradient) - convection (‘solvent drag’/ ‘ultrafiltration’), whereby solutes in the blood are pushed through a membrane by a pressure gradient (analogous to filtration)

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Conventional HD relies predominantly of difussion with a small component of convective transport Sometimes blood purification is performed entirely by convection using a membrane of high permeability (HF). HF can also be combined with dialysis (HDF) but in this case most of the solute removal is by convection and not diffusion

Determinants of solute transport during haemodialysis Determinants of the rate of diffusive solute removal      

Blood flow rate through the dialyser Surface area of the dialysis membrane Permeability of the membrane Dialysate flow rate Concentration gradient across membrane Molecular size of the solute –not only do large molecules move more slowly than small molecules but they may be too large to pass through the membrane pores

Determinants of solute transport during hemodialysis Determinants of the rate of convective solute transport 

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Surface area and water permeability of the membrane Membrane porosity  Blood flow rate through the dialyser Size of the solute Pressure differential across the membrane

Determinants of solute transport during hemodialysis Effect of membrane porosity on solute removal The porosity of the dialysis membrane refers to the size of the molecules that can pass through the pores of the membrane. A highly porous membrane allows movement of large molecules, which would be excluded by a low porosity membrane (pore size