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Tuesday, May 21, 2013
Dialysis is a process by which waste products are removed from the blood and excess fluid is removed from the body. There are two types of dialysis: hemodialysis and periotoneal dialysis.
In hemodialysis, the patient's blood is circulated continuously through a machine that contains a "dialyzer," which is a special type of filter containing thousands of tiny capillaries (hollow fibers) that allow wastes and fluid to be filtered and removed. The procedure generally takes 3-5 hours and is performed three times weekly.
In order to undergo this type of dialysis, a patient first has an operation performed on the arm, allowing blood vessels to enlarge so that needles can easily be inserted into them to connect them to the dialysis machine. There are two types of surgery that may be done:
Fistula - Creation of a "fistula," in which two of the person's own blood vessels, an artery and a vein (in the lower or upper arm), are connected together through a small opening. Blood flow from the artery is partly diverted to the vein, causing the latter to enlarge and develop thicker walls over the next few weeks to months. The thickened vein forms a conduit that allows placement of needles for efficient dialysis.
Graft - Construction of a "graft," in which a synthetic blood vessel, usually made of Gore-tex (the same material as is used for making ski wear), is inserted into the arm (or occasionally the leg), connecting two blood vessels and creating an easily accessible "blood vessel" that can be punctured by needles for dialysis.
The first alternative, fistula construction, is the preferred type of surgery, since it uses only a person's own blood vessels. Graft construction is performed in people who start with small veins, or veins that are not visible on the surface of their arm. In either case, the operation is considered to be minor surgery and is performed on an outpatient basis, usually at least 2 to 3 months before dialysis is anticipated to be needed.
Sometimes the kidneys fail quickly and dialysis needs to be started on an emergency basis, so there is not time for the patient to undergo surgery and await maturation of the fistula or graft. In this case, an IV catheter (the size of a large IV line) can be placed in a vein just beneath the right or left collarbone and can be used immediately for dialysis. Such a catheter can remain in place and be used for weeks or even months if needed, until surgery can be done to construct a fistula or graft.
During the actual procedure of dialysis, the patient usually sits in a lounge chair or lies in a bed, and the arm with the fistula or graft is cleaned with an antibacterial solution. Two needles are then inserted, one to carry blood to the dialysis machine, and one to return it to the body. In cases where the patient has a tunneled catheter as described just above, the catheter is hooked up via tubing to the dialysis machine. The patient's blood flows continuously through the machine, a little at a time, and is cleaned and processed by the dialysis filter. During the procedure, excess fluid can be removed from the person's body as well, allowing swelling in the legs and elsewhere to gradually be reduced.
Because of the removal of fluid and waste products during dialysis, some side effects may occur, including:
This happens especially in the first few dialysis treatments; but as the person's body gradually adjusts to dialysis, the symptoms often improve or disappear. Many people report that they feel better after starting dialysis, because swelling is reduced, appetite improves, and energy level increases.
Because the failing kidney is no longer able to remove waste products and fluid from the body efficiently, anything that a patient eats or drinks in between treatments will accumulate in the body and bloodstream. Patients quickly learn that one of the keys to feeling well with dialysis is to be careful with salt and water intake in between treatments, so as to minimize fluid accumulation and lessen the need for large amounts of fluid removal during dialysis.
The following types of dietary restrictions are needed in dialysis patients:
Salt (sodium) - Salt restriction means: not adding salt to food at the table, not cooking with salt, avoiding most types of fast food, and minimizing the use of most canned foods. If too much sodium is eaten, thirst and water intake follow, leading to swelling of the legs, hands, and face, and even to accumulation of water in the lungs, resulting in shortness of breath.
Potassium - High blood potassium levels may develop, resulting in muscle weakness and even cardiac arrest, so the intake of potassium-rich foods (such as potatoes, oranges, bananas, tomatoes, dried beans, and figs) must be restricted.
Phosphorus - This mineral, which is contained in meat and dairy products, accumulates in the body with kidney failure and results in severe, debilitating effects on muscles, bones, and blood vessels in the long term.
Many research studies are underway to help us learn about hemodialysis. Would you like to find out more about being part of this exciting research? Please visit the following links:
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Last Reviewed: Oct 20, 2011
Mildred Lam, MD
Associate Professor of Medicine
School of Medicine
Case Western Reserve University