An arteriovenous fistula (AVF) represents an intentional connection created between an artery and a vein, which are normally separated components of the circulatory system. This surgical procedure is distinct from a naturally occurring fistula, which is an abnormal connection that can cause various health issues. The primary purpose of the surgically created AVF is to establish a robust and long-lasting access point for a life-sustaining medical treatment.
The AVF is considered the preferred method for providing vascular access in people with kidney failure who require hemodialysis. This specialized connection is typically created in the arm, linking a high-pressure artery directly to a lower-pressure vein. This rerouting of blood flow causes the vein to undergo significant physical changes, making it suitable for repeated cannulation.
Function as Dialysis Access
The arteriovenous fistula is the gold standard for long-term vascular access because it provides the high volume of blood flow necessary for effective hemodialysis. A standard vein cannot handle the rapid, repeated blood removal and return required for the filtering machine, as it would quickly collapse. By linking the artery to the vein, the arterial pressure forces a much greater volume of blood into the vein.
This increased flow rate and pressure cause the vein to enlarge and the walls to thicken over time, a process known as arterialization. The resulting vessel is strong enough to withstand the multiple needle sticks that occur during weekly dialysis treatments. Compared to alternative access methods, such as synthetic grafts or temporary central venous catheters, the AVF has a significantly lower risk of infection and thrombosis, or clotting.
Surgical Creation and Maturation
The creation of an arteriovenous fistula is a relatively minor surgical procedure, often performed on an outpatient basis, typically in the arm, wrist, or elbow. Vascular surgeons most commonly connect the radial artery to the cephalic vein in the forearm (radiocephalic fistula) or the brachial artery to the cephalic or basilic vein in the upper arm (brachiocephalic fistula). The artery and vein are joined together with a suture, creating an anastomosis where the high-pressure flow is introduced into the vein.
Following surgery, the fistula requires a period known as maturation before it can be used for dialysis. This process involves the vein wall thickening and the vessel lumen expanding under the new, higher pressure and flow conditions. Maturation usually takes between six weeks and several months. For a fistula to be deemed mature and ready for use, it must reach a certain diameter, depth, and blood flow rate to sustain efficient dialysis.
Daily Care and Monitoring
Maintaining the function and longevity of the arteriovenous fistula requires proper daily care, including inspection and protection. Patients should wash the area daily with mild soap and water to maintain hygiene and prevent skin infections at the access site. It is important to protect the fistula arm from physical trauma or compression that could cause damage or clotting.
A fundamental part of daily monitoring is feeling for the “thrill,” which is the characteristic buzzing or vibration caused by the turbulent, high-volume blood flow through the connected vessels. The thrill should be checked multiple times a day, as a change in its intensity or a complete loss of the thrill can signal a serious problem. To prevent injury, no blood pressure measurements, blood draws, or intravenous lines should ever be placed in the arm containing the fistula. Furthermore, patients should avoid wearing tight jewelry or clothing that could restrict blood flow in the arm.
Recognizing Complications
While the arteriovenous fistula is generally the most reliable form of dialysis access, several complications can arise that require immediate medical attention. One of the most common issues is stenosis, which is a narrowing of the blood vessel that can impede flow and compromise the effectiveness of dialysis. Stenosis can be suspected if there is a noticeable change in the thrill or an increase in the pressure required to return blood during a treatment session.
Thrombosis, or clotting, is a serious complication signaled by the sudden loss of the thrill; this is a medical emergency that can lead to access failure. Infection at the access site may present as localized redness, swelling, warmth, or pain, and can spread to the bloodstream. Another issue is “steal syndrome,” where blood is diverted from the lower arm or hand into the fistula, causing symptoms like coldness, pain, or numbness in the fingers due to poor circulation.