The kidneys are essential to life function; they help to excrete the normal byproducts of metabolism and regulate the body's fluid status and electrolytes. They can fail because of long standing hypertension or diabetes, infection, drug reaction, or a congenital defect or other anatomic abnormality. In this circumstance, dialysis or kidney transplant are lifesaving.
Hemodialysis involves removing blood from the body, circulating it through a machine (an "artificial kidney") that removes impurities and extra fluid and balances electrolytes, and then returning the filtered blood to the body. Most people go to an outpatient dialysis unit to receive dialysis 3 times a week for about 3 hours at a time. Some people do dialysis at home, others do nighttime dialysis. Your nephrologist helps to determine your schedule.
To achieve good dialysis, you must have a high flow conduit (an "access") to remove and return blood expediently, and this is where a vascular surgeon comes in. There are three types of access: a central venous catheter, an arteriovenous fistula (AVF) or arteriovenous graft (AVG). The catheter is most often considered temporary, because catheters have a high rate of complications: they can dislodge, or become infected, or clot, or damage the central veins in the chest, resulting in arm or facial swelling. The best long-term dialysis access is an AVF. Not all people who need dialysis are good candidates for an AVF, unfortunately, because creating an AVF requires a good arm vein. We discover whether a good arm vein exists by doing a venous mapping, an ultrasound test of the veins, to determine their size and to be sure that they are patent (open) and not damaged from prior intravenous lines or blood draws. If you are have end stage kidney disease and may need for dialysis, we ask that you try to have blood draws from the top of the hand, if possible, to preserve the arm veins.
An AVF or AVG is completely implanted underneath the skin. Nothing is exposed or hangs out of the body between dialysis sessions. When you go to dialysis, two needles are placed into the access and are then connected to the dialysis machine. One needle draws blood out of the body, and the other returns it after it has circulated through the dialysis machine.
Hemodialysis access is not a perfect science. It is not uncommon to require more than one procedure to achieve a stable access, and it may take subsequent procedures to maintain that access. The access is considered your lifeline, and all of us-- the dialysis nurses and technicians, your nephrologist, vascular surgeon and you -- work as a team to help maintain it. Your doctor or nurse will teach you how to check the thrill in your access, and you should do this every day. We will also monitor it closely, by examining it and taking flow readings off the dialysis machine and also by performing a quarterly ultrasound. The ultrasound will help to detect areas of narrowing (stenosis) or bulges (pseudoaneurysms), which may threaten the longevity of your access. Detecting these problems early and fixing them helps us achieve remarkable long term outcomes.
A hemodialysis catheter is a large intravenous line (IV) that is put into the vein at the base of your neck or in your groin. The catheter tip sits in the large vein that drains back to your heart. The other end of the catheter is tunneled underneath the skin and exits the skin on your chest or leg. When you go to dialysis, the end of the catheter is hooked to the dialysis machine. The catheter is split down the center into two channels (ports); through one port, blood is drawn out of the body into the dialysis machine, through the other port, the blood returns from the machine and into the body.
Placing a hemodialysis catheter is a minor surgical procedure and can usually be accomplished in about 30 minutes under a light anesthetic. We typically use ultrasound as well as fluoroscopy (continuous x-ray) to help guide placement of the catheter. Once placed, the catheter is ready for immediate use. It is the only way to receive dialysis if you need it urgently.
Catheters must be maintained carefully. The exit site must be cleaned to avoid infection, and the ports are flushed with heparin after each dialysis session to keep them from clotting. The catheter must be kept dry, so showers and swimming are not permitted. Most catheters are considered temporary because they are associated with more complications than other forms of dialysis access.
Catheters can be removed in the office under a local anesthetic. Removing a catheter takes about 15-20 minutes.
Placing an arteriovenous fistula (AVF) involves connecting a vein to an artery. Arteries take blood from your heart to your arm and are high-flow vessels. Veins take blood the opposite direction, from your arm to your heart, and are lower-flow vessels. A normal arm vein is not big enough and does not have enough flow in it to be able to run dialysis. Also, we would not want to place needles directly into the artery for dialysis, because then we might compromise blood flow to the hand. However, when we hook the vein to the artery, the vein enlarges and becomes thick walled (it becomes like an artery, or "arterializes"). We can then use the vein for dialysis. Most fistulas are placed through a small incision on the arm. The surgery is performed under a local or general anesthetic as an outpatient procedure and generally takes less than an hour. Typically, an AVF requires at least 2-3 months to mature adequately to be used for dialysis. It takes time for the vein to dilate and develop a thick wall that can support the dialysis needles. For this reason, it is important to place the AVF an adequate period of time prior to the time you need to start dialysis in order to avoid the need for a dialysis catheter. Remember, the catheter is the only way we can administer dialysis in an urgent situation. After surgery, do not let anyone draw blood, start an intravenous line, or take a blood pressure on your access arm. This can potentially damage your access.
An arteriovenous graft (AVG) is used if there is no usable vein for an AVF. This procedure involves tunneling a pencil-sized tube (graft) made of Goretex or decellularized cow artery underneath the skin. The graft is sewn to your artery on one end and your vein on the other. When you go to dialysis, the needles are put through the skin into the graft. Like the AVF, the graft is placed through small incisions on the arm. Sometimes if the arms are not favorable, we place AVG in the top of the leg instead. The surgery typically takes about an hour and is performed with a local or light general anesthetic. Because the graft is not your own tissue, it has a higher risk of clotting or getting infected than an AVF. It has, however, the advantage of being able to be used sooner for dialysis. Many AVG can be used within 2 weeks after they are placed. Just like for an AVF, you must protect your access arm. Do not let anyone draw blood, start an IV, or take a blood pressure on that arm.
Every AVF or AVF steals blood that would typically go to the hand; instead it is diverted up through the vein and back to the heart. In most cases, this is well tolerated. It may be associated with some transient numbness or cramping in the hand during dialysis or if the blood pressure is low. Uncommonly, the symptoms can be more severe. Persistent pain, numbness or weakness in the hand must be reported immediately to your surgeon. These symptoms are suggestive of steal syndrome, and may need to be treated with a revisional surgery.