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glossary:hemodialysis

Hemodialysis

A medical procedure that uses a special machine (a dialysis machine) to filter waste products from the blood and to restore normal constituents to it. This shuffling of multiple substances is accomplished by virtue of the differences in the rates of their diffusion through a semipermeable membrane (a dialysis membrane).

Although hemodialysis may be done for acute kidney failure, it is more often employed for chronic renal disease. Hemodialysis is frequently done to treat end-stage kidney disease. Under such circumstances, kidney dialysis is typically administered using a fixed schedule of three times per week.

Catheter, hemodialysis

A venous catheter used for hemodialysis (dialysis of the blood). A hemodialysis catheter is a type of central venous catheter. It may be inserted into the subclavian, internal jugular, or femoral veins. Subclavian catheters generally may be used for 2 to 6 weeks. Hemodialysis catheters are often for relatively short-term use because of an acute need for dialysis or because chronic dialysis is just starting.

Long-term access for hemodialysis may be provided by subcutaneous arteriovenous fistulas in which an artery (the radial artery) is surgically anastomosed (connected) to a vein (the cephalic vein). However, after this procedure is done, it takes 6 to 8 weeks for the forearm veins to dilate and arterialize to be suitable for repeated puncture and hence for long-term hemodialysis.

Dialysis machine

A machine that filters a patient's blood to remove excess water and waste products when the kidneys are damaged, dysfunctional, or missing. Blood is drawn through a specially created vein in the forearm, which is called an arterio-venous (AV) fistula. From the AV fistula, blood is taken to the dialysis machine through plastic tubing. The dialysis machine itself can be thought of as an artificial kidney. Inside, it consists of more plastic tubing that carries the removed blood to the dialyser, a bundle of hollow fibers that forms a semipermeable membrane for filtering out impurities. In the dialyser, blood is diffused with a saline solution called dialysate, and the dialysate is in turn diffused with blood. Once the filtration process is complete, the cleansed blood is returned to the patient. Most patients using dialysis due to kidney impairment or failure use a dialysis machine at a special dialysis clinic. Most sessions take about four hours, and typically patients visit the clinic one to three times per week.

See also: Nephrotic Syndrome

glossary/hemodialysis.txt · Last modified: 2012/10/16 14:40 (external edit)