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What Is Hemodialysis?

Hemodialysis (pronounced: hee-mo-dye-AL-uh-sis) is a kind of kidney dialysis. It's the one that doctors use most often to take over the kidneys' job of filtering the blood.

Why Do People Need Hemodialysis?

Our kidneys work like a garbage collection system. They clean extra fluid and waste from our blood. These wastes then leave the body as urine (pee).

If the kidneys stop working properly, waste can build up in the blood. That can get dangerous. So people with kidney failure need dialysis to filter out the waste.

How Does it Work?

Hemodialysis uses a machine to pull blood out of the body, filter it, and pump the clean blood back into the body again. The actual filtering happens in a part of the machine called a dialyzer, or artificial kidney.

The dialyzer has two parts. One part is for blood. The other is filled with a cleaning solution called dialysate.

The two parts of the dialyzer are separated by a thin membrane. Blood cells and other important parts of the blood are too big to pass through the membrane. But waste products and extra fluids go through it easily.

The dialysate pulls waste and extra fluids out of the blood, through the membrane, and carries them away. The filtered blood is then pumped back to the body.

Blood flows from the body into the machine and back again through tubes. These tubes are attached to needles in the person's skin. The needles go into a large vein or artery through a vascular access. Doctors need to create this vascular access before dialysis can begin.

Creating a vascular access involves minor surgery. Most patients are awake during the procedure, but get local anesthesia to stop feeling in the area. Surgeons usually create the vascular access a few weeks before hemodialysis starts. That way, the vascular access has time to heal.

There are three different kinds of vascular access, but they all do the same job:

  • Fistulas and grafts connect arteries to veins to make a bigger blood vessel. Surgeons usually create these types of vascular access in a person's arm.
  • Sometimes doctors use a catheter to gain access to the blood vessels. Catheters used for dialysis may go in the neck, chest, or other part of the body. They're usually temporary until the person can get a fistula or graft.

When Is it Done?

Hemodialysis usually takes about 4 hours and has to be done three times a week. Most people go to a special clinic — called a dialysis center — to get their treatments. Some people get treatments at a hospital. Occasionally, dialysis centers train families to do the treatments at home, but this isn't common.

After being hooked up to dialysis machines, patients lie down or sit in a chair. While the treatment is going on, they might use the time to read, watch TV, play videogames, or nap.

Are There Any Risks?

Some people feel the needles as they go into the vascular access. After that, dialysis treatments are painless.

Hemodialysis does have some risks, including:

  • Infection. Germs can get into the body at the site of a vascular access and cause an infection.
  • Low blood pressure. Some people's blood pressure drops during treatment. When this happens, the person might have trouble breathing, have a headache, and feel sick (or throw up).
  • Itching. Hemodialysis can cause a person's skin to feel itchy, especially during or right after a treatment.
  • Sleep problems. Some people getting dialysis can have trouble sleeping (insomnia) or develop sleep apnea (when someone stops breathing for a short time during sleep).

What Can I Do to Feel Better?

If you're doing dialysis, it helps to stay healthy. Taking good care of yourself helps you avoid problems and get the most out of your treatments. Here are a few tips:

  • Eat the right foods. You'll need to get the right amount — not too much or too little — of fluids, salt, vitamins, and minerals each day. Too much potassium or phosphorus, for example, can affect your heartbeat or weaken your bones. Your doctor or a dietitian at your dialysis clinic can give you advice on the right meal plan for you.
  • Take medicine if your doctor prescribes it. You'll probably need medicines to control your blood pressure, help produce red blood cells, and control nutrient levels in your blood. Follow your doctor's instructions, and talk to your doctor before taking any nonprescription medicines, vitamins, or other supplements.
  • Plan ahead. If you'll be traveling, make sure you'll be able to continue your treatments. If you need to go to a dialysis clinic in a different town, call ahead and make sure they can fit you into their schedule.

Looking Ahead

Kidney dialysis is a treatment for kidney disease — it steps in to do the job of the kidneys and keep the body in balance. But it's not a cure. Dialysis alone won't heal a person's failing kidneys.

Some kinds of kidney disease get better and the person doesn't need dialysis anymore. Other people stop getting dialysis because they have a kidney transplant.

Some people need dialysis treatments for the rest of their lives. In these cases, people might switch back and forth between hemodialysis and another type of dialysis called peritoneal dialysis, which usually can be done at home.

Reviewed by: Joshua J. Zaritsky, MD, PhD
Date Reviewed: Jan 14, 2020

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