Principles of Dialysis
- Diffusion,
- Osmosis, and
- Ultrafiltration
are the principles on which hemodialysis is based.
Diffusion
The toxins and wastes in the blood are removed by diffusion— they move from an area of higher concentration in the blood to an area of lower concentration in the dialysate.
Osmosis
Excess water is removed from the blood by osmosis -- water moves from an area of higher solute concentration (the blood) to an area of lower solute concentration (the dialysate bath).
Ultrafiltration
Ultrafiltration - water moves under high pressure to an area of lower pressure. This process is much more efficient at water removal than osmosis. Ultrafiltration is accomplished by applying negative pressure or a suctioning force to the dialysis membrane. Because patients with renal disease usually cannot excrete water, this force is necessary to remove fluid to achieve fluid balance.
