Types of Vein Access for Dialysis
Hemodialysis, the process of cleaning the blood of people suffering from kidney failure, is usually performed three times a week. Two needles are inserted into the patient. Blood is drawn, cleaned via circulation through a filter in the dialysis machine and returned to the blood stream.
What is Vein Access for Dialysis?
Vein access makes the dialysis treatment possible by allowing the blood stream to be easily accessed each time. Vein access is obtained via a surgically created vein (usually placed in the arms), which is used to remove the blood and return it to the body after filtering. Vein access allows approximately 500 ml/min of blood to flow through the hemodialysis machine ,cleaning as much blood as possible per treatment.
The procedure is usually performed on an outpatient basis, and is done under local anesthesia. The procedure should be done several weeks or months before the first dialysis treatment as to allow for sufficient maturing of the vein, needed in order to reduce the risk of low blood flow, blood clots, weak veins and more.
Types of Vein Access in Dialysis
There are three types of vein access used in dialysis: arteriovenous (AV) fistula, arteriovenous graft and central venous catheter.
– Arteriovenous Fistula
The arteries carry blood from the heart to the body, while veins carry blood from the body back to the heart. A vascular surgeon makes a connection between an artery and a vein to allow vascular access. This connection causes extra pressure, the amount of blood flowing into the vein increases, the vein becomes larger and the vein walls thicker. The larger vein provides easy and reliable dialysis access to the blood vessels, and makes it possible for the vein to be punctured repeatedly without collapsing. The process, known as maturation, typically takes 2-3 months to be completed (although it can take up to 1 year to occur). If an arteriovenous fistula fails to mature, surgery must be repeated. The procedure requires advance planning and is usually started 6 months prior to when the first dialysis treatment is estimated to be needed.
The arteriovenous fistula is considered to be a preferred type of vein access, due to a relatively low rate of infection and clot formation. It also provides a good blood flow and lasts longer than other types of accesses.
– Arteriovenous Graft
In this type of vein access, artificial tubing is attached on one end to an artery and on the other to a vein. The tube is placed under the skin and is punctured during the dialysis. The graft can be used as soon as 2-3 weeks after the procedure.
The arteriovenous graft has a 2-3 year life span, and is more prone to infections and clotting then the fistula. Repeated blood clots can block the flow of blood through the graft.
– Venous Catheter
A plastic tube is inserted into a large vein, usually in the neck, chest or in leg near the groin. The tube splits in two when exiting the body, and is connected to the dialysis machine.
The venous catheter tends to clog up and is not as efficient for dialysis as the other types of vein access. This is usually a temporary method, used in cases when urgent dialysis is needed or if other methods of vein access are not possible.