Dialyser Health Dictionary

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Dialyser: From 1 Different Sources

(dialyzer) n. a medical device designed to allow controllable transfer of solutes and water across a semipermeable membrane separating blood and *dialysate solutions flowing countercurrent to each other. Most modern dialysers are based on hollow-fibre technology and are tube-shaped. Blood enters the top of the tube and travels, by capillary action, down a large number of hollow microfibres, which are embedded in polyurethane at each end of the dialyser tube for support. Dialysate enters the tube from the side, near the bottom of the tube. It runs in the opposite direction to the blood, around the hollow fibres and separated from the blood by the semipermeable membrane that constitutes the microfibre wall. A number of different dialyser membranes are in use, displaying a wide variety of permeabilities (related to pore size), biocompatibilities (not activating *cytokine or alternate pathway *complement responses in the blood), and costs.
Health Source: Oxford | Concise Colour Medical Dictionary
Author: Jonathan Law, Elizabeth Martin

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.... dialysis

Haemodialysis

A method of removing waste products or poisons from the circulating blood using the principle of DIALYSIS. The procedure is used on patients with malfunctioning or non-functioning KIDNEYS. It is done using an arti?cial kidney or dialyser which restores blood to its normal state. The process has to be repeated, sometimes for many months, until a donor kidney is available for transplantation to replace the patient’s failing one.... haemodialysis

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