Vascular Access for Dialysis
Dialysis is a blood-cleansing procedure used as treatment for severe kidney failure. The chief function of the kidneys is to filter waste products and excess fluid from the body. When the kidneys fail, dialysis is performed to remove toxins and fluids. Dialysis can be performed by hemodialysis which cleans the blood directly through a machine, or with peritoneal dialysis which involves using sterile fluid instilled into the abdominal cavity. This topic will cover vascular access for hemodialysis.
Types of Vascular Access
During hemodialysis, blood is removed from a vein, circulated through a filtering machine, and returned to the body. In order to perform hemodialysis, access to the bloodstream must be obtained. This can be done with a dialysis catheter, a large IV in the neck or upper leg, or through a surgical connection between an artery and vein in the arm (or leg) called a fistula or graft.
An arteriovenous (AV) fistula is the surgical connection of an artery to a vein.To create a fistula, a surgeon connects one of the patient's arteries in the arm (or leg) to a nearby vein. This surgical connection increases blood flow and strengthens the vein over time. The vein's increased strength create a durable access site for blood to be removed through a needle, sent to the dialysis machine for cleaning, and returned to the body through a second needle.
A fistula takes a minimum of 2-3 months for the vein to "mature" and be strong enough to tolerate the needle sticks required for hemodialysis. Fistulas are considered the best option for dialysis access, however, because they tend to be more durable and have a lower risk of infection compared to grafts or catheters.
Small veins that will not properly develop into a fistula require a graft to connect the vein to the nearby artery. Grafts are tubes created out of synthetic material that are implanted under the skin in the arm. The graft can be accessed with needles for hemodialysis. rather than the unsuitable vein. Unlike a fistula, a graft can be used immediately, though most patients will wait until post-operative swelling improves before using the graft.
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. These catheters are large IV's that are placed in the neck or upper leg, with 2 ports that are extend outside the body to bring the blood to and from the dialysis machine.
Complications of Hemodialysis Access
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
Depending on the complication that arises, treatment may include antibiotics, removal/replacement of the catheter, and angioplasty or stenting of the fistula or graft. In more severe cases, a new access may need to be placed.