What Is Hemodialysis?

Although healthy kidneys have several functions in the body, the most well-known job is to produce urine. When kidney function goes below 10 to 15 percent, kidneys are no longer able to filter the blood and make urine. This causes toxins to build up in the body along with excess fluid. Fortunately, there are treatments and medicines that can replace the functions of the kidneys and keep the body alive. One type of treatment that replaces kidney function is hemodialysis. Hemodialysis is a therapy that filters waste, removes extra fluid and balances electrolytes (e.g., sodium, potassium, bicarbonate, chloride, calcium, magnesium, phosphate).

How is hemodialysis done?

In hemodialysis, blood is removed from the body and filtered through a man-made membrane called a dialyzer, or artificial kidney, and then the filtered blood is returned to the body. The average person has about 10 to 12 pints of blood; during dialysis only one pint (about two cups) is outside of the body at a time. To perform hemodialysis there needs to be an access created to get the blood from the body to the dialyzer and back to the body. There are three access types for hemodialysis: arteriovenous (AV) fistula, AV graft and central venous catheter. The AV fistula is the vascular access most recommended by the dialysis community; however, you and your doctor will decide which access is best for you.

When a patient goes to hemodialysis, a nurse or technician will check vital signs and get the patient’s weight. The weight gain will tell how much excess fluid the patient has to have removed during the treatment. The patient is then “put on the machine”. Blood never actually goes through the dialysis machine. The dialysis machine is like a big computer and a pump that keeps track of blood flow, blood pressure, how much fluid is removed and other vital information. It mixes the dialysate, or dialysis solution, which is the fluid bath that goes into the dialyzer. This fluid helps pull toxins from the blood, and then the bath goes down the drain.

How does hemodialysis work?

The dialyzer is the key to hemodialysis by acting as an artificial kidney that filters the blood. The dialyzer is a hollow plastic tube about a foot long and three inches in diameter that contains many tiny filters. There are two sections in the dialyzer; the section for dialysate and the section for the blood. The two sections are divided by a semipermeable membrane with microscopic holes that allow water and waste to cross the membrane.

How often is hemodialysis done?

Blood needs to flow through the dialyzer for several hours to adequately clean the blood and rid the body of excess fluid. Traditional, in-center hemodialysis is generally done three times a week for about four hours each session. Alternative hemodialysis schedules include nocturnal and short daily. With nocturnal hemodialysis, the patient has dialysis for about eight hours overnight while sleeping. Short daily hemodialysis is performed five or six times per week for about two to three hours each treatment.

Advantages and disadvantages of hemodialysis

Hemodialysis is an effective treatment for those with end stage renal disease. However, hemodialysis alone will not provide a complete treatment for those with kidney failure. Diet and fluid restrictions need to be followed, and medicines may need to be taken to replace other functions of the kidneys, such as regulating blood pressure and stimulating production of red blood cells to prevent anemia.

For those who choose in-center hemodialysis, some of the benefits are that they will have their treatments performed in a dialysis center by trained professionals. They can spend their time in dialysis sleeping, reading, writing, watching television, listening to music or doing other quiet activities. There are four days a week when they will not have to go to dialysis. Some of the disadvantages are that they will have to travel to and from hemodialysis three times each week. The diet restrictions include limiting foods that contain phosphorus, potassium and sodium and drinking a limited amount of fluid. Some people report a “washed out” feeling after hemodialysis. Those who perform nocturnal hemodialysis (in center or at home) report that this washed out feeling is not as common. Also, because nocturnal dialysis is performed during nonproductive sleeping hours, many people report they feel that their lives are more “normal.”

How can I find out more about hemodialysis?

Talk to your doctor about hemodialysis. You may also schedule a visit to a DaVita dialysis center in your area. To arrange your tour, call DaVita Guest Services at 1-800-244-0680.

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