Healthy kidneys clean your blood and remove extra fluid in the form of urine. They also make substances that keep your body healthy. However, your kidneys may shut down suddenly (acute kidney injury) after a severe illness, complicated surgery, heart attack or other serious problem. Certain medications also can cause kidney injury.
Common causes of kidney failure include:
- Diabetes
- High blood pressure (hypertension)
- Kidney inflammation (glomerulonephritis)
- Blood vessel inflammation (vasculitis)
- Kidney cysts (polycystic kidney disease)
Dialysis replaces some of the functions performed by the kidneys when your kidneys no longer work. There are two different types of dialysis – hemodialysis and peritoneal dialysis.
Hemodialysis is a treatment to filter wastes and water from your blood, as your kidneys did when they were healthy. It helps control blood pressure and balance important minerals, such as potassium, sodium, and calcium, in your blood. It can help you feel better and live longer, but it’s not a cure for kidney failure.
When is dialysis needed?
You need dialysis if your kidneys no longer remove enough wastes and fluid from your blood to keep you healthy. This usually happens when you have only 10 to 15 percent of your kidney function left. You may have symptoms such as nausea, vomiting, swelling and fatigue. However, even if you don’t have these symptoms yet, you can still have a high level of wastes in your blood that may be toxic to your body. Your doctor is the best person to tell you when you should start dialysis. Your doctor uses your estimated glomerular filtration rate (eGFR) to measure your level of kidney function. Your eGFR is calculated using your blood creatinine test results, sex, age and other factors. A normal value varies with age. This measure of your kidney function can help to plan your treatment, including when to start hemodialysis.
How does hemodialysis work?
In hemodialysis, a dialysis machine and a special filter called an artificial kidney, or a dialyzer, are used to clean your blood. Blood enters at one end of the filter and is forced into many, very thin, hollow fibers. As your blood passes through the hollow fibers, dialysis solution passes in the opposite direction on the outside of the fibers. Waste products from your blood move into the dialysis solution. Filtered blood remains in the hollow fibers and returns to your body.
In the filter, your blood flows inside hollow fibers that filter out wastes and extra salt and water.
Your nephrologist—a doctor who specializes in kidney problems—will prescribe a dialysis solution to meet your needs. The dialysis solution contains water and chemicals that are added to safely remove wastes, extra salt, and fluid from your blood. Your doctor can adjust the balance of chemicals in the solution if
- your blood tests show your blood has too much or too little of certain minerals, such as potassium or calcium
- you have problems such as low blood pressure or muscle cramps during dialysis
How does the dialyzer clean my blood?
The dialyzer, or filter, has two parts, one for your blood and one for a washing fluid called dialysate. A thin membrane separates these two parts. Blood cells, protein and other important things remain in your blood because they are too big to pass through the membrane. Smaller waste products in the blood, such as urea, creatinine, potassium and extra fluid pass through the membrane and are washed away.
Where is hemodialysis done?
Hemodialysis can be done in a hospital, in a dialysis center that is not part of a hospital or at home. You and your doctor can decide which place is best, based on your medical condition, and your wishes.
How frequently do I need to undergo hemodialysis?
Dialysis can be carried out as follows:
- At a dialysis centre or hospital: 3 treatments a week for about 4 hours
- short daily hemodialysis—5 to 7 days per week for 2 to 4 hours at a time
- nightly home hemodialysis—three to six times per week while you sleep
Healthy kidneys work 24 hours a day, 7 days a week. Getting more hemodialysis feels more like having healthy kidneys and lowers your chances for problems that are common with a standard hemodialysis schedule
How do I prepare for dialysis?
Preparation for hemodialysis starts several weeks to months before your first procedure. To allow for easy access to your bloodstream, a surgeon will create a vascular access. The access provides a mechanism for a small amount of blood to be safely removed from your circulation and then returned to you in order for the hemodialysis process to work. Dialysis moves blood through the filter at a high rate. Blood flow is very strong. The machine withdraws and returns almost a pint (about 500 ml) of blood to your body every minute. The access will be the place on your body where you insert needles to allow your blood to flow from and return to your body at a high rate during dialysis.
The surgical access needs time to heal before you begin hemodialysis treatments.
There are three types of vascular accesses:
Arteriovenous (AV) fistula. A surgically created AV fistula is a connection between an artery and a vein, usually in the arm you use less often. This is the preferred type of access because of effectiveness and safety.
- AV graft.If your blood vessels are too small to form an AV fistula, the surgeon may instead create a path between an artery and a vein using a flexible, synthetic tube called a graft.
- Central venous catheter.If you need emergency hemodialysis, a plastic tube (catheter) may be inserted into a large vein in your neck or near your groin. The catheter is temporary.
Care of your access
Your access is your lifeline. You will need to protect your access. Wash the area around your access with soap and warm water every day. Check the area for signs of infection, such as warmth or redness. When blood is flowing through your access and your access is working well, you can feel a vibration over the area. Let your dialysis center know if you can’t feel the vibration.
How does hemodialysis proceed?
- Your weight, blood pressure, pulse and temperature are checked. The skin covering your access site — the point where blood leaves and then re-enters your body during treatment — is cleansed.
- During hemodialysis, two needles are inserted into your arm through the access site and taped in place to remain secure. Each needle is attached to a flexible plastic tube that connects to a dialyzer. Through one tube, the dialyzer filters your blood a few ounces at a time, allowing wastes and extra fluids to pass from your blood into a cleansing fluid called dialysate. The filtered blood returns to your body through the second tube.
- You may experience nausea and abdominal cramps as excess fluid is pulled from your body — especially if you have hemodialysis only three times a week rather than more often. If you’re uncomfortable during the procedure, ask your care team about minimizing side effects by such measures as adjusting the speed of your hemodialysis, your medication or your hemodialysis fluids.
- Because blood pressure and heart rate can fluctuate as excess fluid is drawn from your body, your blood pressure and heart rate will be checked several times during each treatment.
- When hemodialysis is completed, the needles are removed from your access site and a pressure dressing is applied to prevent bleeding. Your weight may be recorded again. Then you’re free to go about your usual activities until your next session.
What changes will I have to make when I start hemodialysis?
You have to adjust your life to build your dialysis treatment sessions into your routine. If you have in-center dialysis, you may need to rest after each treatment. You will have to change what you eat and drink. Your health care team may adjust the medicines that you take.
Make changes to what you eat and drink
If you’re on hemodialysis, you may need to limit
- sodium in foods and drinks.
- high-phosphorus foods.
- the amount of liquid you drink, including liquid found in foods. Fluid builds up in your body between hemodialysis treatments.
You may also need to
- add protein to your diet because hemodialysis removes protein
- choose foods with the right amount of potassium
- take vitamins made for people with kidney failure
- find healthy ways to add calories to your diet because you may not have a good appetite
How will I know if my hemodialysis is working?
You’ll know your hemodialysis treatments are working by how you feel. Your energy level may increase and you may have a better appetite. Hemodialysis reduces salt and fluid buildup, so you should have less shortness of breath and swelling as well.
Do I need to eat a special diet?
Yes. Generally speaking, patients on dialysis are advised to increase their protein intake and limit the amount of potassium, phosphorus, sodium, and fluid in their diet. Patients with diabetes or other health conditions may have additional diet restrictions. It’s important to talk with you dietitian about your individual diet needs.
Your dialysis care team will monitor your treatment with monthly lab tests to ensure you get the right amount of dialysis and that you are meeting your dietary goals.
What are possible problems from hemodialysis?
You could have a problem with your vascular access, which is the most common reason someone on hemodialysis needs to go to the hospital. Any type of vascular access may
- become infected
- have poor blood flow or blockage from a blood clot or scar
These problems can keep your treatments from working. You may need to have more procedures to replace or repair your access for it to work properly.
Sudden changes in your body’s water and chemical balance during treatment can cause additional problems, such as
- muscle cramps.
- a sudden drop in blood pressure, called hypotension. Hypotension can make you feel weak, dizzy, or sick to your stomach.
Your doctor can change your dialysis solution to help avoid these problems. The longer and more frequent treatments of home hemodialysis are less likely to cause muscle cramps or rapid changes in blood pressure than standard in-center dialysis.
You can lose blood if a needle comes out of your access or a tube comes out of the dialyzer. To prevent blood loss, dialysis machines have a blood leak detector that sets off an alarm. If this problem occurs at the clinic, a nurse or technician will be on hand to act. If you’re using home dialysis, your training will prepare you and your partner to fix the problem.
Can dialysis patients continue to work?
Yes. Many dialysis patients continue to work or return to work after they have gotten used to dialysis. If your job has a lot of physical labor (heavy lifting, digging, etc.), you may need to change your duties. For more information on working with kidney disease click here.
Can dialysis cure my kidney disease?
In some cases of sudden or acute kidney failure, dialysis may only be needed for a short time until the kidneys get better. However, when chronic kidney disease progresses to kidney failure over time, your kidneys do not get better and you will need dialysis for the rest of your life unless you are able to receive a kidney transplant.
Can the dialyzer do everything my kidneys once did?
No. Hemodialysis can replace part, but not all, of your kidney function. Dialysis will help improve your energy level, and changes you make to your diet can help you feel better. Limiting how much water and other liquid you drink and take in through foods can help keep too much fluid from building up in your body between treatments. Medicines also help you maintain your health while on dialysis.
What are the factors which determine the success rate of hemodialysis?
If you had sudden (acute) kidney injury, you may need hemodialysis only for a short time until your kidneys recover. If you had reduced kidney function before a sudden injury to your kidneys, the chances of full recovery back to independence from hemodialysis are lessened.