Vascular Access and Hemodialysis

Role of Kidneys

Kidneys perform important functions in a healthy person:

• They clean the blood by removing excess fluid, minerals and wastes.
• They make hormones that keep bones strong and blood healthy.

Failing kidneys result in a buildup of harmful wastes in the body, possible increases in blood pressure, retention of excess fluid and less-than-adequate production of red blood cells.

Hemodialysis

Patients with kidney failure need treatment to replace the work of these vital organs. Through a process called hemodialysis, the blood is allowed to flow, a few ounces at a time, through a special filter that removes wastes and extra fluids. The clean blood is then returned to the body. By removing the harmful wastes and extra salt and fluids, hemodialysis helps control blood pressure and maintains the proper balance of chemicals such as potassium and sodium in the body.

Vascular Access

Preparing vascular access is an important step before regular hemodialysis sessions. This is the site on the body where blood is removed and returned during dialysis. To maximize the amount of blood cleansed during hemodialysis, the vascular access is created to provide high volumes of continuous blood flow during treatments. There are several types of vascular accesses:

Arteriovenous (AV) Fistula

An AV fistula requires advance planning because a fistula takes some time after surgery to develop. But a well-formed fistula is less likely than other kinds of vascular accesses to form clots or become infected and may last much longer than other approaches.

An AV fistula is created by connecting an artery directly to a vein, usually in the forearm. This causes more blood to flow into the vein, and as a result, the vein grows larger and stronger, making hemodialysis treatments easier.

Arteriovenous Graft

For those who have small veins that won’t develop properly into a fistula, vascular access can be achieved with a synthetic tube implanted under the skin in the patient’s arm. The tube serves as an artificial vein that can be used for needle placement and blood access during hemodialysis. A graft can be used sooner than an AV fistula after placement, often within two or three weeks.

Compared with fistulas, grafts may have more problems with clotting or infection and need replacement sooner, but a well-cared-for graft can last for several years.

Venous Catheter for Temporary Access

Patients whose kidney disease progresses rapidly may not have time to get a permanent vascular access before they start hemodialysis treatments. A venous catheter may then be used as a temporary access.

A catheter (tube) is inserted into a vein in the neck, chest or leg near the groin. Its two chambers allow two-way flow of blood. Once a catheter is placed, needle insertion is not needed. However, catheters are not ideal for permanent access as they can clog, become infected or cause narrowing of the veins in which they are placed.