In order to perform any type of dialysis treatment, an access is required. The access provides a convenient entryway into your body. The access that is required to perform peritoneal dialysis is different from the access needed to perform hemodialysis. The vascular access is so important that it is sometimes referred to as your "lifeline." Proper care of your access is essential in order for it to last and function properly. Let's take a look at the variety of accesses available.
Vascular Access for Hemodialysis
One important step before starting regular hemodialysis sessions is preparing the vascular access, which is the site on your body where blood is removed and returned during dialysis. The dialysis access provides a way for blood to flow from your body to the dialyzer for cleaning and then back to your body. To maximize the amount of blood cleansed during hemodialysis treatments, the vascular access should allow your blood to flow at the rate ordered by your doctor. Ideally, a vascular access should be placed weeks or months before you start dialysis. The early placement of the vascular access will allow sufficient time for the access to heal and mature. The three basic kinds of vascular access for hemodialysis are an arteriovenous (AV) fistula, an arteriovenous (AV) graft, and a venous catheter. The peritoneal dialysis catheter will be discussed later.
Arteriovenous or AV Fistula
An AV fistula requires advance planning because a fistula takes a while after surgery to develop—usually from two to six months. A properly formed fistula is less likely than other kinds of vascular accesses to form clots or become infected. Also, properly formed fistulas tend to last years longer than any other kind of vascular access.
A surgeon creates an AV fistula by connecting an artery directly to a vein, usually in the wrist or forearm. It is preferred that the fistula be placed in the arm you use the least. Connecting the artery to the vein causes more blood to flow into the vein. You will be able to feel the vibration or pulse of the blood flowing through your access. The vibration you feel is sometimes referred to as the "buzz." This feeling is called a thrill. Your healthcare professional will also listen for the blood flowing in your access with a stethoscope. The "whoosh" sound that is heard through the stethoscope is called a bruit (pronounced brew-ee). You will become familiar with how to check your access daily to make sure it is working properly. The high blood flow from the artery through the vein helps the access grow larger and stronger, making needle insertions for hemodialysis treatments easier. The fistula takes some time to develop. You will need to exercise the arm with the fistula to help it develop. For the surgery, you'll be given a local anesthetic. In most cases, the procedure can be performed on an outpatient basis. Although it is the preferred access, small veins or other conditions could make it difficult for some people to have a successful fistula. Your surgeon may order a test (vessel mapping) to check the size and quality of your veins and blood flow to determine the best access for you. These and other problems with vascular access can be corrected when determined in the early stages. Your healthcare team will monitor your access regularly to help you keep your access healthy and working properly.
Here are some key points to consider before fistula placement:
- The arm that will have the fistula placed needs special care to preserve the veins and improve the chance to obtain a well functioning fistula. Therefore, it is a good idea to limit the drawing of blood to the arm that will not be receiving the fistula.
- Some patients can improve the veins in the arm to be used for their fistula by exercising that arm (squeezing a soft foam ball with a tourniquet placed around the upper part of that arm). Although this approach does not work for all patients, it still may be worth a try.
In order to preserve your AV fistula, your healthcare team may introduce a special technique for needle insertion called the Buttonhole Technique. This technique can only be used with an AV fistula. Inserting needles into the access is called cannulation. Buttonhole is a special cannulation method where an individual cannulates the AV fistula in the exact same spot, at the same angle and depth every treatment. The track is a tunnel that is created by the formation of scar tissue similar to the hole created in an earlobe for a pierced earring. This track goes from the surface of your skin to the outside wall of your fistula. Special needles are required for the buttonhole technique. Once the track is well healed, there are no nerves or tissue in the path of the needle to cause you pain. This method is best suited for the person who chooses to self-cannulate (inserting your own needles) or may be used by the dialysis clinic staff. Several other methods of cannulation can also be used, and can be discussed with your healthcare team.
Even when proper techniques are used, problems can occur. The most common problem with the AV fistula is a condition known as stenosis in which there is narrowing of the blood vessel, which may lead to decreased blood flow or clotting.
Arteriovenous AV Graft
If you have small or weak veins that won't develop properly into a fistula, you can have a vascular access placed that connects an artery to a vein using a synthetic tube, or graft, implanted under the skin in your arm. The graft is usually a soft, man-made tube that connects to an artery on one end and to a vein on the other end, allowing blood to flow through it. The artificial graft material is used for needle placement for blood access during hemodialysis. A graft does not need as long to develop as a fistula does, so it can be used sooner after placement, often within two to four weeks. The thrill (vibration felt due to the high blood flow) can also be felt in a graft, and the bruit ("whooshing" noise) can be heard with a stethoscope if the graft is functioning properly. You will become familiar with how to check your access daily to make sure it is working properly. Compared with properly formed fistulas, grafts tend to have more problems with clotting and infection and need replacement sooner. However, a well-cared-for graft can last several years.
Caring for Your Vascular Access (Fistula and Grafts)
Listed below are a few things you need to know in order to care for your vascular access.
- Find out from your surgeon which way the blood is flowing within your access and which area is used for the arterial needle and venous needle.
- To develop your new fistula, be sure to exercise your access arm by squeezing a foam ball or using hand grips as directed. This helps the fistula develop properly.
- Keep your access clean at all times.
- Check for the "thrill" (vibration) in your access every day. The "thrill" tells you that the blood is flowing through your access as it should be. If you do not feel the "thrill," you should call your nephrologist or nurse.
- Wash the skin over the access with soap and water daily to decrease the risk of infection.
- Your access site is only to be used for dialysis treatments.
- Do not allow blood to be drawn from the access.
- Do not let anyone put a blood pressure cuff on your access arm.
- Be careful not to bump or cut your access.
- Do not scratch your access site as the scratching can increase the risk for infection if the surface of the skin is broken.
- Do not wear jewelry or tight clothes over your access site.
- Do not sleep with your access arm under your head or body.
- Do not lift heavy objects, carry children, or put pressure on your access arm.
- Report any areas of your graft or fistula that appear to be protruding or ballooning out. This is called an aneurysm. The skin over an aneurysm may look thin and shiny.
- Watch for signs and symptoms of infection. If you see any of the symptoms below occurring at your access site, be sure to report them to your nephrologist or nurse.
- Pus or drainage
Preparing for Cannulation (Needlesticks)
When the needles are inserted into your vascular access for hemodialysis, it is called cannulation. Proper cannulation is an important factor in keeping your access healthy and working properly. The dialysis staff is trained to insert the needles properly. Let's review how the needles work. One needle pulls the blood from the vascular access while the other needle returns the cleaned blood back to you. The needles are large in order to get proper blood flow for your dialysis treatment. The better the blood flows to the dialyzer, the better your blood will be cleaned. The amount of discomfort you feel from each needle insertion varies from person to person. Your facility may offer various methods in order to decrease the discomfort you may feel. It is important to share your concerns with the dialysis staff so that they can make needle insertions more comfortable for you. You may even learn to do this yourself! Ask your nephrologist or nurse if you are interested in learning how to stick yourself. This is called self-cannulation.
A catheter is a flexible, hollow tube inserted into a large vein in your neck, chest, or leg near the groin which allows the blood to flow into and out of your body. A catheter is most commonly used as a temporary dialysis access. There are several places on your body where a catheter can be placed. The most common are:
- Internal jugular catheter - inserted into the jugular vein on the side of the neck.
- Subclavian catheter - placed into the subclavian vein under the collar bone on the chest.
- Femoral catheter - placed in the large vein in the leg near the groin.
A catheter has two chambers to allow a two-way flow of blood. One chamber allows blood to flow out of the body to be cleaned and the other chamber allows cleaned blood to return to the body. Catheters contain an exit site where the catheter comes out of the skin. This is covered by bandages or other types of dressings. These dressings need to be changed and kept clean and dry at all times. Some catheters require stitches at the exit site where the catheter comes out of your skin to help hold the catheter in place. Some catheters tunnel under the skin and have a small bulged area near the exit site called a "cuff." The cuff remains under the skin and helps to hold the catheter in place and helps to prevent infection.
Catheters are not the ideal permanent access, but, if your kidney disease has progressed quickly or you are waiting for your permanent access to mature or heal, you may need to have a catheter placed as a temporary access. The type of catheter you have placed usually depends on how long you will need to have the catheter.
Catheters do not usually allow for a large volume of blood to flow to the dialyzer which can result in a less efficient treatment. Catheters can clot, become infected, and can cause narrowing of the veins (stenosis) in which they are placed. However, if you need to start hemodialysis immediately, a catheter will work for several weeks or months while your permanent access develops.
For some people, fistula or graft surgery is unsuccessful, and they will need to use a permanent catheter as their long-term access. Catheters that will be needed for more than about three weeks are designed to be tunneled under the skin to increase comfort and reduce complications. Even tunneled catheters are prone to infection. The catheter will have an exit site which is covered with a protective bandage. These bandages must be changed and kept dry at all times.
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