In 1943, Dr. Willem Kolff built the first hemodialysis machine. Yet it took two more decades before chronic dialysis was practical. Why? Because a new artery and vein had to be used for each treatment and then tied off afterward. Thus, only a few treatments could be done.Vascular access— a reusable way to get blood from the body to the artificial kidney and back—was what made dialysis possible.
Today, you can have a good life for many years on dialysis. But vascular access is still the biggest challenge for long-term treatment.
Arteries and veins
A vascular access uses your blood vessels. You have two types of vessels:
- Large, strong vessels that carry blood from your heart—at high pressure—to the rest of your body. They have a smooth, inner layer (called intima) so blood cells won't stick as they pass through. The inner layer is surrounded by flexible muscle, to help push the blood along, and then an outer cover of tissue. Most arteries are deep below the skin and muscle, which protects them from injury.
- Carry blood back to your heart. Since this blood is under less pressure, veins are not as strong as arteries: they have the same layers, but each one is thinner. Veins are closer to your skin's surface and easy to reach with needles*, though, which makes them more useful for hemodialysis.
An ideal access would be under the skin, to reduce infection. It would be easy to reach—like a vein—but strong enough to handle the blood flow rates needed for dialysis—like an artery. It would heal itself after each needle stick, and last for decades with no problems.
* Afraid of needles? You're not alone! Read anotherHome Dialysis Centralarticle calledDialysis Needle Fear - Easing the Sting.
Fistulas are best
A fistula (surgical connection between a vein and an artery under the skin) is as close as we can get today to an ideal access. When a fistula is made, fast blood flow from the artery arterializesthe vein—the layer of muscle in the vein becomes larger and stronger. This takes time.
If you will need dialysis, it's best to get a fistula a few months ahead of time so it can mature and be ready to use. Getting a fistula at least four months before you start dialysis can reduce your risk of sepsis (blood poisoning).1Having a fistula when you start treatment also reduces costs five-fold,2which may save you money.
A good fistula can last for decades. Because it uses only your own artery and vein, it is less prone to infection, blood clots, and narrowing (stenosis) than other types of access. It heals itself after each needle stick. You are less likely to need hospital stays to fix a fistula. You may even live longer. In a U.S. random study of 5,507 people on dialysis, those with fistulas were significantly more likely to live than those with a graft (next best) or catheter. This was true even after adjusting for age and other illnesses.3
Fistulas are the "gold standard" for dialysis access. In fact, fistulas are so much better that Medicare has a program calledFistula First.4This program aims to raise the U.S. rate of fistula placement and help ensure that anyone who can have a fistula will get one.
How do you know if you can have a fistula? The best way to be sure is to ask your nephrologist to refer you to avascular(blood vessel) surgeon who does many fistulas. Then, ask the vascular surgeon to dovessel mapping— an ultrasound to look at your veins and arteries. With vessel mapping, the surgeon can make a plan for which vessels will work best. Sometimes the best plan is totransposea large vein (move it closer to the surface of your skin). Get a second opinion if you are told that you can't have a fistula.
Using a fistula for dialysis
It is vital that a new fistula becannulated(have needles placed) by an experienced care team member—or that you learn to do it yourself. The fewer people who cannulate a fistula, the longer it is likely to last. Putting in your own needles hurts less, because you are distracted by what you're doing. And, since you can feel both ends of the needles, you have the best chance of success.
There are two ways to cannulate a fistula:
- Site Rotation- at each treatment, the needles are placed 1-1.5 inches away from the last sites, using a pattern that goes up and down the length of the fistula. This keeps any one spot from being weakened by too many needles, and should help prevent aneurysms (ballooning out of a weak spot in the fistula wall).
- The Buttonhole Technique- at each treatment, the same person (best if it's you) puts needles in the same holes at the same angle. In a few treatments (8 or so), a track forms, like a pierced earring hole. Then, special blunt needles are used in the tracks. Cannulation is nearly painless, and the technique is said to reduce infection and aneurysm, though there are few published studies of it.
Making a fistula last
While fistulas are best, they are not perfect. New fistulas can fail to mature. And sometimes a good fistula is made, but then damaged.
- A needle can infiltrate through the fistula wall so blood leaks out into your tissues—if it is not placed correctly. Infiltration can cause painful bruising, and damage to the intima layer can cause blood clots to form. Some blood clots can be dissolved with drugs. Or, some fistula damage can be repaired by a surgeon.
- Any time your blood pressure drops, blood flow through your fistula slows down. Slower blood flow can allow time for blood clots to form. Squeezing your fistula with tight elastic sleeves, a wristwatch, or carrying a purse that dangles over your fistula arm can also slow blood flow and lead to clots.
- If the skin over your fistula is not clean, the needles can carry bacteria into your blood. This can cause life-threatening infection (sepsis). Learn how to clean your fistula arm, so you know it's done right. Wear gloves to cannulate your fistula. If you don't cannulate your own fistula, watch to be sure the staff put on clean gloves.
- A fistula can shunt too much blood away from your hand, so it is cold and painful. This is called steal syndrome. New blood vessels may grow, or a surgeon can try to limit blood flow to the access. A new access may be needed.
Other types of access: grafts and catheters
If a fistula is not possible, there are two other types of access:
- A graft
- Links your artery and vein, under the skin, with a piece of artificial vein. Grafts are foreign to your body, and more likely to get infected. They don't have the smooth, intima lining of a real blood vessel, so they are more likely to clot. Grafts can't heal themselves after needle sticks, so they wear out in a few years and need to be replaced. Steal syndrome and narrowing are more likely in a graft than a fistula, too. All in all, you are more likely to have hospital stays with a graft than a fistula. It is also not possible to use the buttonhole technique on a graft. If a graft fails, it may be possible to create a fistula—ask your vascular surgeon.
- A central venous catheter
- A y-shaped plastic tube inserted into a large vein in the neck (usually the internal jugular). It may be tunneled under the skin so it comes out of the chest. One end of the catheter is in or near the heart. The other end has two tubes, one to bring blood to the artificial kidney and one to bring it back to the body. Because a catheter can be placed very quickly and used right away, it is often used as temporary access, and any patient may have one at some point. Since a catheter goes through the skin, it is a portal for bacteria. Infection (sepsis) can occur, and is more likely if the catheter gets wet or the dressing is not changed correctly. Catheters make it hard to bathe and impossible to swim. It's best to use a catheter for the shortest possible time.
Your dialysis lifeline
Vascular access is what makes hemodialysis possible. If you can have a fistula, learn how to care for it—after the surgery as well as down the road. You'll need to listen with a stethoscope each day for the bruit (whooshing noise) a healthy fistula should make, and feel for the thrill(buzzing pulse) to be sure they are the same. Changes in either can mean stenosis or a blood clot. You'll want to check your fistula for signs of infection, like redness or warmth. And think about learning to put in your own needles—it's the best way to help your fistula last.
For more information about fistulas, check out:
- Oliver MJ, Rothwell DM, Fung K, Hux JE.Late creation of vascular access for hemodialysis and increased risk of sepsis.J Amer Soc Nephrol.15:1936-1942, 2004.
- Lee H, Manns B, Taub K, Ghali WA, Dean S, Johnson D, Donaldson C.Cost analysis of ongoing care of patients with end-stage renal disease: The impact of dialysis modality and dialysis access.Am J Kidney Dis.Sept;40(3):611-622, 2002.
- Dhingra RK, Young EW, Hulbert-Shearon TE, Leavey SF, Port FK.Type of vascular access and mortality in U.S. hemodialysis patients..Kidney Int.Oct;60(4):1443-51, 2001.
- Fistula First website.