principles
Last reviewed 01/2018
Blood is passed through an extracorporeal circulation into a dialyser where it is kept separate from dialyser fluid by an artificial semi-permeable membrane.
Solutes diffuse across the membrane in both directions, the direction for a particular solute being governed by the composition of dialysate fluid and blood.
Ultrafiltration, the removal of plasma water, is achieved by applying a relative positive pressure to the blood. It may be used alone, without diffusion, to reduce fluid overload.
Traditionally, the membrane is composed of cuprophane, a derivative of cellulose. More recently, synthetic membranes of polymeric structure are used as they are associated with less activation of humoral factors and less damage to blood cells.