A filtering technique used to remove waste products from the blood and excess fluid from the body as a treatment for kidney failure. The kidneys normally filter about 1,500 litres of blood daily. They maintain the fluid and electrolyte balance of the body and excrete wastes in the urine. Important elements, such as sodium, potassium, calcium, amino acids, glucose, and water are reabsorbed. Urea, excess minerals, toxins, and drugs are excreted. Dialysis is used to perform this function in people whose kidneys have been damaged due to acute kidney failure or chronic kidney failure. Without dialysis, wastes accumulate in the blood. In chronic kidney failure, patients may need to have dialysis several times a week for the rest of their lives or until they can be given a kidney transplant. In acute kidney failure, dialysis is carried out more intensively until the kidneys are working normally.
There are 2 methods of dialysis: haemodialysis and peritoneal dialysis. In both methods, excess water and wastes in the blood pass across a membrane into a solution (dialysate), which is then discarded. Haemodialysis filters out wastes by
passing blood through an artificial kidney machine.
The process takes 2–6 hours.
Peritoneal dialysis makes use of the peritoneum (the membrane that lines the abdomen) as a filter.
The procedure is often carried out overnight or continuously during the day and night.
Both types of dialysis carry the risk of upsetting body chemistry and fluid balance.
There is also a risk of infection within the peritoneum in peritoneal dialysis.
A procedure used to ?lter o? waste products from the blood and remove surplus ?uid from the body in someone who has kidney failure (see KIDNEYS, DISEASES OF). The scienti?c process involves separating crystalloid and COLLOID substances from a solution by interposing a semi-permeable membrane between the solution and pure water. The crystalloid substances pass through the membrane into the water until a state of equilibrium, so far as the crystalloid substances are concerned, is established between the two sides of the membrane. The colloid substances do not pass through the membrane.
Dialysis is available as either haemodialysis or peritoneal dialysis.
Haemodialysis Blood is removed from the circulation either through an arti?cial arteriovenous ?stula (junction) or a temporary or permanent internal catheter in the jugular vein (see CATHETERS). It then passes through an arti?cial kidney (‘dialyser’) to remove toxins (e.g. potassium and urea) by di?usion and excess salt and water by ultra?ltration from the blood into dialysis ?uid prepared in a ‘proportionator’ (often referred to as a ‘kidney machine’). Dialysers vary in design and performance but all work on the principle of a semi-permeable membrane separating blood from dialysis ?uid. Haemodialysis is undertaken two to three times a week for 4–6 hours a session.
Peritoneal dialysis uses the peritoneal lining (see PERITONEUM) as a semi-permeable membrane. Approximately 2 litres of sterile ?uid is run into the peritoneum through the permanent indwelling catheter; the ?uid is left for 3–4 hours; and the cycle is repeated 3–4 times per day. Most patients undertake continuous ambulatory peritoneal dialysis (CAPD), although a few use a machine overnight (continuous cycling peritoneal dialysis, CCPD) which allows greater clearance of toxins.
Disadvantages of haemodialysis include cardiovascular instability, HYPERTENSION, bone disease, ANAEMIA and development of periarticular AMYLOIDOSIS. Disadvantages of peritoneal dialysis include peritonitis, poor drainage of ?uid, and gradual loss of overall e?ciency as endogenous renal function declines. Haemodialysis is usually done in outpatient dialysis clinics by skilled nurses, but some patients can carry out the procedure at home. Both haemodialysis and peritoneal dialysis carry a relatively high morbidity and the ideal treatment for patients with end-stage renal failure is successful renal TRANSPLANTATION.
n. a method of separating particles of different dimensions in a liquid mixture, using a thin semipermeable membrane whose pores are too small to allow the passage of large particles, such as proteins, but large enough to permit the passage of dissolved crystalline material. A solution of the mixture is separated from distilled water by the membrane; the solutes pass through the membrane into the water while the proteins, etc., are retained. The principle of dialysis is used in the *dialyser (see also haemodialysis). The peritoneum is used as an autogenous semipermeable membrane in the technique of *peritoneal dialysis.
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