The specific feature of haemodialysis (HD) is that it is an extracorporeal treatment; (occurs outside of the body), the blood is pumped from the patient via a bloodline through a filter (dialyser) with the aid of a sophisticated dialysis machine for purification.
During this procedure the amount of blood which remains outside your body is about one teacup; for satisfactory treatment, an average of at least 4 hours per session is needed, generally on alternate days. In the filter, the blood passes through very thin capillaries which have a spongy surface (membrane).

Toxins in the blood (which are small in size), are able to pass through the holes in the membrane but do not allow larger molecules, such as albumin and proteins, which are important for the body, to pass through. The purified blood then goes back into normal circulation inside the body. It is important that the filter membrane does not cause a reaction when it comes in contact with the patient’s blood.

Nowadays there are a large number of “highly biocompatible” membranes which solve problems of this kind; the most widely used is Polysulfone, which Fresenius has now developed further to produce Helixone®.