Dialysis, short for hemodialysis, is the blood-cleansing procedure most commonly 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 this function. During dialysis, blood is removed from a vein in the patient’s arm or leg, circulated through a filtering machine, and returned to the body through an artery.
Reasons for Dialysis
Dialysis is necessary as a treatment for patients with end-stage kidney disease or permanent kidney failure. Usually, a patient requires dialysis if 85 to 90 percent of kidney function has been lost. In some cases, only temporary dialysis may be needed until kidney function returns. If dialysis is being used for kidney failure, however, it will be employed permanently or until 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 more blood to flow. The vein’s increased strength and capacity helps 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 three times a week for three to five hours. When beginning treatment, it is important for doctors and patients to determine the most appropriate point of vascular access, which is the site on the body where blood is removed and returned during dialysis. This area is usually prepared a few weeks before dialysis begins to allow for more efficient removal and replacement of your blood with fewer complications.
The three basic types of vascular access for dialysis treatments are:
An arteriovenous, or AV fistula is the surgical connection of an artery to a vein. This creates a stable access site and provide ample blood flow for patients undergoing long-term dialysis treatments. The AV fistula is created during a minor outpatient procedure that is performed under local anesthesia.
Although they typically take three to six months to mature, fistulas are considered the best option for dialysis access. Doctors prefer to use fistulas over alternative methods such as artificial grafts and catheters because fistulas tend to be more durable and have a lower risk of complications.
Small veins that won’t develop properly into a fistula, require vascular access that connects an artery to a vein using a synthetic tube, or graft, 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. A graft does not need to develop as a fistula does, so it can be used sooner after placement, often within two or three weeks.
Venous Catheters for Temporary Access
With kidney disease that has progressed quickly, patients may not have time to get a permanent vascular access before they start hemodialysis treatments. In those cases, a venous catheter may be used as a temporary access. Catheters are not ideal for permanent access.
Complications of Vascular Access
As with any type of treatment, there are certain risks associated with all three types of vascular access that may include:
- Blood clots
- Low blood flow
These complications are considered minor, and tend to occur most often in venous catheters. Doctors may prescribe medications to correct these problems, or may need to remove the access point with additional surgery. The methods of vascular access are typically very effective in assistance with the dialysis procedure.