AV FISTULA CREATION

Definition:An arteriovenous fistula is a disruption of the normal blood flow pattern. Normally, oxygenated

blood flows to the tissue through arteries and capillaries. Following the release of oxygen in the tissues, the blood returns in veins to the heart. An arteriovenous fistula is an abnormal connection of an artery and a vein. The blood bypasses the capillaries and tissues and returns to the heart. Arterial blood has a higher blood pressure than blood in veins. Although both the artery and the vein retain their normal connections, the new opening between the two causes some arterial blood to shunt (be diverted) into the vein because of the blood pressure difference. As a result, the vein swells. An AV fistula has proven to be the best kind of vascular access for people whose veins are large enough, not only because it lasts longer but it is also less likely than other types of access to form clots or become infected. If the veins are not large enough, or there is no time to wait for a fistula to develop, a graft or a catheter must be used.

Purpose:The surgical creation of an AV fistula provides a long-lasting site through which blood can be

removed and returned during hemodialysis. The fistula, which allows the person to be connected to a dialysis machine, must be prepared by a surgeon weeks or months before dialysis is started. When the vein and artery are joined, the vein gradually becomes larger and stronger, creating the fistula that provides vascular access years longer than other types of access and with fewer complications.

Sometimes dialysis is only needed temporarily, but some people need it for the rest of their lives or until a kidney is available for a transplant. When kidney failure is diagnosed, time is needed to prepare the patient's body with either an AV fistula or implantable devices that will connect the person to the dialysis machine.

Procedure:AV (arteriovenous) fistulas are recognized as the preferred access method. To create a fistula, a

vascular surgeon joins an artery and a vein together through anastomosis. Since this bypasses the capillaries, blood flows rapidly through the fistula. One can feel this by placing one's finger over a mature fistula. This is called feeling for "thrill" and produces a distinct 'buzzing' feeling over the fistula. One can also listen through a stethoscope for the sound of the blood "whooshing" through the fistula, a sound called bruit.

Fistulas are usually created in the nondominant arm and may be situated on the hand (the 'snuffbox' fistula'), the forearm (usually a radiocephalic fistula, or so-called Brescia-Cimino fistula, in which the radial artery is anastomosed to the cephalic vein), or the elbow (usually a brachiocephalic fistula, where the brachial artery is anastomosed to the cephalic vein). A fistula will take a number of weeks to mature, on average perhaps 4–6 weeks. During treatment, two needles are inserted into the fistula, one to draw blood and one to return it.

The advantages of the AV fistula use are lower infection rates, because no foreign material is involved in their formation, higher blood flow rates (which translates to more effective dialysis), and a lower incidence of thrombosis. The complications are few, but if a fistula has a very high blood flow and the vasculature that supplies the rest of the limb is poor, a steal syndrome can occur, where blood entering the limb is drawn into the fistula and returned to the general circulation without entering the limb's capillaries. This results in cold extremities of that limb, cramping pains, and, if severe, tissue damage. One long-term complication of an AV fistula can be the development of an aneurysm, a bulging in the wall of the vein where it is weakened by the repeated insertion of needles over time. To a large extent the risk of developing an aneurysm can be reduced by careful needling technique. Aneurysms may necessitate corrective surgery and may shorten the useful life of a fistula. To prevent damage to the fistula and aneurysm or pseudoaneurysm formation, it is recommended that the needle be inserted at different points in a rotating fashion. Another approach is to cannulate the fistula with a blunted needle, in exactly the same place. This is called a 'buttonhole' approach. Often two or three buttonhole places are available on a given fistula. This also can prolong fistula life and help prevent damage to the fistula.

Submitted By:Pahati, Sheila Mae R.

BSN-125 G-100B