Arteriovenous (AV) Fistula — The Gold Standard Hemodialysis Access
Once kidney function goes below 10 to 15 percent of normal, dialysis treatments or a kidney transplant are necessary to sustain life.
There are two types of dialysis: hemodialysis and peritoneal dialysis (PD). Both dialysis treatments are able to replace the kidneys’ function of cleaning the blood of toxins and removing extra fluids for people with kidney failure.
Hemodialysis cleans blood by removing it from the body and passing it through a dialyzer, or artificial kidney. The dialyzer is a filter with two parts: one for blood and another for dialysis fluid, called dialysate. The filter between these two parts has very small pores, allowing some tiny particles to pass through. The particles that are filtered include the toxins that need to be removed from the body such as urea, creatinine and potassium, while larger blood cells and protein the body needs cannot pass through. The filtered blood is then returned to the body.
The process of removing blood from the body, filtering it and returning it takes time. Hemodialysis treatment usually takes three to five hours and is repeated three times a week.
The type of access a person has is important for getting the best dialysis possible. There are three types of access: catheter, arteriovenous (AV) graft and arteriovenous (AV) fistula.
Catheter for hemodialysis
For dialysis, a catheter is inserted into a large vein in either the neck or chest. A catheter is usually a short-term option; however, in some cases a catheter is used as a permanent access. With most dialysis catheters, a cuff is placed under the skin to help hold the catheter in place. The blood flow rate from the catheter to the dialyzer may not be as fast as for an AV graft or AV fistula; therefore, the blood may not be cleaned as thoroughly as with an arteriovenous access.
Catheters have a greater tendency to become infected than the other access types because the device is both inside and outside of the body. A catheter must always be kept clean and dry; swimming or bathing are usually restricted. Getting dressed may disturb the catheter at the exit site, so care needs to be taken.
Arteriovenous (AV) graft for hemodialysis
An arteriovenous (AV) graft is created by connecting a vein to an artery using a soft plastic tube. After the graft has healed, hemodialysis is performed by placing two needles; one in the arterial side and one in the venous side of the graft. The graft allows for increased blood flow. Grafts tend to need attention and upkeep. Taking good care of your access may limit problems.
Arteriovenous (AV) fistula for hemodialysis
A fistula used for hemodialysis is a direct connection of an artery to a vein. Once the fistula is created it is a natural part of the body. This is the preferred type of access because once the fistula properly matures and gets bigger and stronger; it provides an access with good blood flow that can last for decades. After the fistula is surgically created, it can take weeks to months before the fistula matures and is ready to be used for hemodialysis. People with kidney disease can do exercises including squeezing a rubber ball to strengthen the fistula before use.
Fistula — the gold standard access
The National Kidney Foundation (NKF), Centers for Medicare and Medicaid Services (CMS), DaVita Patient Citizens (DPC) and other organizations and experts generally agree that fistulas are the best type of vascular access. Low rates of complications, clotting and infection all contribute to the fistula’s reputation as the “gold standard” of vascular access.
Dialysis experts also generally agree that the safest and longest lasting of the access types is the AV fistula.
Because a fistula is made by connecting a vein to an artery, the vein becomes bigger allowing for increased blood flow. The fistula is created from natural parts of the body and can be repeatedly “stuck” to perform hemodialysis treatments.
A fistula is the “gold standard” because:
- It has a lower risk of infection than grafts or catheters
- It has a lower tendency to clot than grafts or catheters
- It allows for greater blood flow, increasing the effectiveness of hemodialysis as well as reducing treatment time
- It stays functional for longer than other access types; in some cases a well-formed fistula can last for decades
- Fistulas are usually less expensive to maintain than synthetic accesses
While the AV fistula is the preferred access, there are some people who are unable to have a fistula. If the vascular system is greatly compromised, a fistula may not be attempted. Some people have had fistulas surgically created, but the fistula never matured; therefore, could not be used. Some of the drawbacks of fistulas are:
- A bulge at the access site that some people feel is unattractive
- Taking several months to mature
- Sometimes never maturing at all
“Fistula First” initiative
The Centers for Medicare & Medicaid (CMS) and members of the renal community have come together to start the “Fistula First” initiative (National Vascular Access Improvement Initiative) with the goal of expanding the number of patients with fistulas, as opposed to catheters or grafts.
“When I entered practice in the mid-1970s there were fewer than 10,000 end stage renal disease (ESRD) patients receiving hemodialysis,” said Lawrence Spergel, an expert on ERSD who spoke with the Institute for Healthcare Improvement (IHI). “That number has increased to almost 300,000 patients today. In every community, there are patients whose lives depend on dialysis, which, in turn, depends on a well-functioning vascular access. This [ESRD] population will continue to grow because more and more of these patients are living longer. However, for hemodialysis patients to live long and productive lives, optimal vascular access and care are required.”
Further, synthetic accesses account for an estimated $1 billion in complications costs for Medicare, according to IHI. The CMS has put that number at $1.5 billion.
According to Fistula First, even people with other access types are still good candidates for fistulas. Studies have shown that when patients who have exhausted permanent access sites are re-evaluated and undergo vessel mapping, at least two-thirds are found to be candidates for an AV fistula.
To date, the initiative has overreached its goal of 40 percent of prevalent patients with fistulas. For 2010 the bar has been raised, with the hope being that 50 percent of all new people on hemodialysis will have a fistula and 66 percent of continued patients will use a fistula.
Cleanliness is one way someone on hemodialysis can keep their fistula uninfected. Keep an eye out for infections, which can often be detected when there is pain, tenderness, swelling or redness around the access area. If you notice fever, contact your health care professional. Your doctor may prescribe antibiotics for an infection, which should likely go away easily with early diagnosis.
Unrestricted blood flow
Any restriction of blood flow can cause clotting. Here are some tips to help keep blood flowing without restriction:
- Avoid tight clothing or jewelry that could put pressure on your access area
- Do not carry bags, purses or any type of heavy item over your access area
- Don’t let anyone put a blood pressure cuff on your access arm — have your blood pressure taken from your non-access arm
- Request that blood being drawn is taken from your non-access arm
- Don’t sleep with your access arm under your head or pillow
- Check the pulse in your access daily
The vibration of blood going through your arm is called the “thrill.” You should check this several times a day. If the “thrill” changes or stops a blood clot may have formed. By immediately contacting your doctor or dialysis health care team the clot may be quickly dissolved or removed.
Using a stethoscope, or even putting your ear to the access, you can hear the sound of blood flowing through your access. This sound is called the “bruit.” If the sound gains in pitch and sounds like a whistle, your blood vessels could be tightening (called stenosis). If the tightening becomes too severe, blood flow could be cut off completely.
During dialysis, your pre-pump arterial pressure is monitored. This will tell you how difficult it is for the blood pump to draw blood from your access. If the number is negative, there could be a restriction of blood flow through your fistula.
Good needle sticks
There are two different strategies for using a needle on a fistula: the ladder and the buttonhole techniques, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).
The ladder technique requires that you or your dialysis care provider “stick” the fistula in a different place along the length of the fistula every time. This is called “climbing,” and it saves you from weakening a certain area by repeatedly sticking it. It also provides time for the puncture site to heal.
The buttonhole technique is quite the opposite. Instead of “climbing” the fistula, needle sticks are limited to one site, which is used repeatedly. For the buttonhole technique it is best for only one person to do the stick each time. By going into the access at the same depth and angle — in the same spot — the access has fewer traumas. This concept is similar to sticking an earring through a pierced ear. Scar tissue will develop at the stick site making it easier and less painful to insert the needle. This technique is usually preferred by people who stick themselves.
For those who are able to have a fistula, that should be their access of choice. In addition to being a natural option with a longer life and fewer complications than other access types, a fistula allows for more blood flow which gets blood cleaner during hemodialysis.
If you have questions about your access, please talk to your doctor or dialysis healthcare team.