Dialysis is an artificial method of purifying the blood in individuals with kidney failure. It helps in removing the impurities and waste products from the blood. Dialysis access is a method of gaining access into the bloodstream through blood vessels for dialysis.
During dialysis your physician will use the dialysis access to remove some amount of blood from the body which is allowed to circulate in the dialysis machine to remove the impurities, regulate body water and maintain electrolyte balance. Once the blood is purified in the dialysis machine it is returned to your body through the dialysis access.
Selection of dialysis access location is very important because selecting an access area with decreased circulation may result in inadequate blood flow. Certain conditions such as atherosclerosis may limit blood flow and is more common in the legs than arms. Therefore, a common site used for dialysis access is through the blood vessels of the arms.
Before creating a dialysis access your vascular surgeon may order blood flow tests in the arms and legs such as ultrasound, X-ray and venogram to check if the veins are large enough to use.
Dialysis can be performed using two different methods, peritoneal dialysis and haemodialysis. Peritoneal uses the peritoneal membrane, the lining of your abdomen whereas haemodialysis uses a special type of filter to filter the blood and get rid of harmful wastes, extra salt and water.
Dialysis access can be temporary or permanent:
Temporary access: Dialysis catheters are recommended for temporary access; a hollow tube is placed in the large vein to support the blood flow. Dialysis catheters are used for emergencies and for short periods of time. Tunnelled catheters can be used for longer periods if needed.
Permanent access: Permanent access is surgically created by an arteriovenous fistula (AVF) or arteriovenous (AV) graft.
- AV fistula– AV fistula is created by joining a large vein under the skin to a nearby artery. The large vein is divided and stitched to the opening made at the side of artery. As a result, blood flows down the arteries into the hand. The blood which flows in the divided vein will return to the heart through other veins and the remaining blood in the artery will flow to the hand.
- AV Graft – The connection between an artery and vein can be made using a synthetic bridge. Grafts are used only if your vein is too small or if it is blocked. Your surgeon uses an artificial plastic graft, autograft, or xenograft (tissue from another species). One end of the graft is stitched to one end of your vein and the other end is connected to an artery. The graft is either placed straight or as a loop under the skin of the lower arm or upper arm.
Fistulas and grafts mature over time with the vein becoming larger and stronger, enabling the physician to use larger dialysis needles allowing for more efficient dialysis. Compared to the fistula, grafts mature quicker however the disadvantage with grafts is the increased chance of infection.