Dialysis Access for Hemodialysis
Patients with kidney failure may need to undergo dialysis (cleaning of the blood) to survive.
Hemodialysis is a mechanical method of dialysis, which uses a machine to filter wastes from the blood. There are three different types of accesses for hemodialysis, each with advantages and disadvantages:
AV fistula is when a vein is surgically connected to an artery, allowing a large amount of blood to flow through the vein. As a result, the vein will increase in size to enable rapid removal, cleaning, and return of blood back to the individual.
The AV fistula is considered the best long-term vascular access for hemodialysis, because it provides adequate blood flow and has a lower complication rate than other types of accesses. Most fistulas can take six weeks to three months to mature (be ready to use for dialysis). Some can take longer.
Creating an AV fistula requires a quality vein. An experienced physician can create an AV fistula in about 80 percent of patients.
If an AV fistula cannot be created, a synthetic tube called an AV graft can be implanted under the skin to connect an artery to a vein. AV grafts can generally be used in two to three weeks but, compared to fistulas, have a higher rate of infection and thrombosis. Grafts have a patency (staying open) rate of 50 to 70 percent per year.
When a patient needs to start hemodialysis urgently and does not have time to have a permanent vascular access constructed, a venous catheter can provide temporary access. A catheter is a tube inserted into a vein in the neck or groin. Catheters are not ideal for permanent access due to their high rate of infection and thrombosis. They can also cause narrowing of the veins. Ninety percent of patients should have the catheter replaced by a fistula or graft within three months to avoid serious complications.
