Artificial kidney is a haemodialysis machine through which the toxic substances are removed from the blood of a person whose kidneys are completely damaged.
Haemodialysis (Gr. haima = blood, dia = through, lyo = separate) is the process of diffusion across a semipermeable membrane to remove unwanted substances from the blood while adding desirable components. The pores in the membrane allow some substances to pass through, however, prevent others. The patient is connected to the machine by a tube attached to an artery often the radial artery.
Blood from the artery is pumped into a tube that runs through the dialyzer. The dialyzer is filled with dialysing fluid which contains the same quantities of electrolytes and nutrients as normal plasma but contains no waste products. The cellophane tube (a tube bounded by thin membrane) is kept in the dialysing fluid.
The membrane of the cellophane tube is impermeable to blood cells and proteins but permeable to urea, uric acid, creatinine and mineral ions. So these wastes diffuse from the blood to the dialysing fluid across the cellophane membrane.
Thus the blood is cleared of nitrogenous waste products without losing plasma proteins. Now the blood is returned to the patient’s body through a vein usually the radial vein. Haemodialysis saves and prolongs the life of many patients. At a time about 500 ml of blood is passed through the artificial kidney. Dialysis is done usually thrice a week in severe uremia. Each time the artificial kidney is used for about 6 hours.
Dr. Belding H. Scribner was inventor of this device that made kidney dialysis possible. There is an another type of dialysis called continuous ambulatory peritoneal dialysis (CAPD), which is more convenient and less time-consuming for many patients.
It is considerably less expensive. It is alternative to haemodialysis. It is commonly called peritoneal dialysis. CAPD uses the peritoneum instead of cellophane sheets as the dialyzing membrane.
Since the peritoneum is a semipermeable membrane, it permits rapid transfer of substances, A catheter is placed in the patient’s peritoneal cavity and connected to a supply of dialyzing fluid. Gravity feeds the solution into the abdominal cavity from its plastic container. When the process is complete, the dialyzing fluid is returned from the abdominal cavity to the plastic container and then discarded.