Vascular Access for Dialysis
Dialysis, short for "hemodialysis," is a blood-cleansing procedure used as treatment for chronic kidney failure. The chief function of the kidneys is to filter waste products from the blood. When the kidneys fail, dialysis takes over their function. During dialysis, blood is removed from a vein in the patient's arm (the leg is also used, albeit much less frequently), circulated through a filtering machine, and returned to the body through an artery. Before dialysis begins, a point of vascular access (the site where blood is removed and returned) must be created.
Reasons for Dialysis
Dialysis is necessary for patients who have end-stage kidney disease or permanent kidney failure. Usually, dialysis is required when 85 to 90 percent of kidney function has been lost. In some cases, only temporary dialysis is needed until kidney function returns. When treating kidney failure, however, dialysis is lifelong, unless the patient receives a kidney transplant.
Vascular Access for Dialysis
Because veins tend to have weak blood flow, doctors often connect one of the patient's nearby arteries to the vein being accessed for dialysis. This increases blood flow and strengthens the vein, which in turn allows for more blood to flow. The vein's increased strength and capacity help to create a durable access site, and provide ample blood flow for patients undergoing long-term dialysis.
Types of Vascular Access
Dialysis treatments are usually administered 3 times a week for 3 to 5 hours. A few weeks before dialysis begins, the most appropriate point of vascular access, of which there are three basic types, must be prepared.
An arteriovenous (AV) fistula is the surgical connection of an artery to a vein. It creates a stable access site, and provides ample blood flow for patients undergoing long-term dialysis. An AV fistula is created during a minor outpatient procedure that is performed under local anesthesia.
Although they typically take 3 to 6 months to mature, fistulas are considered the best option for dialysis access. Doctors prefer to use fistulas over alternative methods (see below) because fistulas tend to be more durable, and have a lower risk of complications.
Small veins that will not properly develop into a fistula require vascular access that connects an artery to a vein using a graft (synthetic tube) implanted under the skin in the arm. The graft becomes an artificial vein that can be used repeatedly for needle placement and blood access during hemodialysis. Unlike a fistula, a graft can be used fairly soon after placement, often within 2 to 3 weeks.
Venous Catheters for Temporary Access
With kidney disease that has progressed quickly, there may not be enough time to create permanent vascular access before the start of hemodialysis. In those cases, a venous catheter is used as a temporary access.
Complications of Vascular Access for Dialysis
As with any type of treatment, there are certain risks associated with all three types of vascular access. They include the following:
- Blood clots
- Low blood flow
These complications are considered minor, and tend to happen with venous catheters. Antibiotics or blood thinners may be prescribed to correct these problems, or it may be necessary to surgically remove the access point.