Tag: haemodialysis

Haemodialysis is a method that is used to achieve the extracorporeal (procedure takes place outside the body) removal of waste products such as creatinine and urea from the blood when the kidneys are in a state of renal failure.

The dialysis fluid contains water, glucose, salts and various substances at the correct concentration for the body. The dialysing membrane allows small particles such as water, urea and mineral ions to pass through it. There will be a net flow from the region of higher concentration (usually in the blood) to the region of lower concentration (in the dialysis fluid) by diffusion. As a result, the concentration of these small particles ends up being the same on both sides of the membrane. So the blood leaving the dialysis machine has all these substances in the same concentration as the dialysis solution. The fresh dialysis solution does not contain urea - so urea (and other impurities) pass out of the blood. They are taken away by the flow of dialysis solution. Proteins and blood cells are too big to pass through the membranes, so stay in the blood.

A number of techniques are developed for separating, analyzing, and isolating the various macromolecular constituents of cells and tissues. All these techniques that principally work on the separation of proteins (and enzymes), peptides, carbohydrates, oligonucleotides and nucleic acids are electrophoresis, chromatography and ultracentrifugation. However, separation of macromolecules from the molecules and ions can also be done by using semipermeable membranes, such as those prepared from cellophane or collodion to separate solutes on the basis of molecular weight differences. The technique is called as dialysis and was first described in 1861 by T. Graham.