An arteriovenous (AV) fistula is a surgically created connection between an artery and a vein. This procedure provides a robust and accessible site for needles used in hemodialysis, a treatment for kidney failure. The fistula allows blood to flow directly from an artery into a vein, causing it to enlarge and strengthen. This modification ensures the vein can withstand repeated needle insertions and manage the high blood flow rates necessary for efficient blood filtration during dialysis.
Why Dialysis Requires Special Access
Hemodialysis, a life-sustaining treatment for individuals with kidney failure, relies on a continuous, high-volume flow of blood to effectively remove waste products and excess fluid from the body. Regular veins cannot handle the repetitive needle insertions and rapid blood flow rates required for dialysis sessions, which filter about a pint of blood per minute. Repeated use of smaller veins would lead to their collapse or damage, making long-term access impossible.
An AV fistula is the preferred long-term vascular access for hemodialysis. This preference stems from its superior durability and lower rates of complications, such as infection and clotting, compared to other access methods like central venous catheters or synthetic grafts. The direct connection between an artery and a vein allows for a larger, stronger blood vessel, sustaining consistent dialysis treatments over many years.
Creating an AV Fistula
Creating an AV fistula involves a minor surgical procedure where a vascular specialist connects an artery to a nearby vein. This connection allows high-pressure arterial blood to flow directly into the vein. The increased blood flow and pressure cause the vein to gradually widen and thicken, a process known as maturation.
Maturation is a period after surgery, taking several weeks to months. During this time, the vein transforms into a resilient vessel capable of enduring repeated needle insertions for dialysis. Successful maturation ensures the fistula can provide the necessary blood flow for effective dialysis treatment. Regular monitoring, including physical examination and ultrasound, helps assess this development and detect early issues.
Using and Caring for an AV Fistula
Once an AV fistula has matured, it becomes the access point for hemodialysis treatments. During a session, two needles are inserted into the fistula: one to draw blood for filtration by the dialysis machine, and another to return the cleansed blood to the body. Each dialysis treatment lasts three to four hours, with patients typically requiring three sessions per week.
Proper daily care of the fistula arm is important to maintain its function and prevent complications. Protect the fistula from injury, avoid wearing tight clothing or jewelry on that arm, and never allow blood pressure measurements or blood draws from the fistula arm. Avoid sleeping on the fistula arm to prevent restricting blood flow. Regular hand-arm exercises, such as squeezing a sponge ball, can help maintain blood flow.
Daily, check the fistula’s function by feeling for a vibration, known as a “thrill,” and listening for a “whooshing” sound, called a “bruit.” The thrill indicates proper blood flow, while the bruit confirms continuous flow. Report any decrease or absence of the thrill or bruit, or changes in their usual sound, to a healthcare provider immediately, as these can signal a problem. Maintaining good hygiene by washing the arm daily with soap and water, especially before dialysis, helps prevent infection.
Common Concerns and Management
Despite their advantages, AV fistulas can develop issues requiring medical attention. One common concern is infection, which, though less frequent than with other access types, can occur. Symptoms include warmth, redness, swelling, pain, or pus around the site, sometimes accompanied by fever or chills. Infections are managed with antibiotics, though severe cases may require surgical intervention.
Another problem is clotting, which can block blood flow through the fistula. This can occur in areas of narrowing, known as stenosis, which reduces blood flow and hinders effective dialysis. Stenosis can be treated with angioplasty, a procedure that uses a balloon to widen the narrowed vessel, or minor surgery to repair the site. Swelling in the arm, particularly if persistent beyond two weeks, may indicate an underlying issue like central vein occlusion.
Less common concerns include “steal syndrome,” where the fistula diverts too much blood from the hand, leading to coldness, numbness, or pain in the hand or fingers. Management involves procedures to limit blood flow to the fistula. Promptly report any unusual symptoms or changes in the fistula, such as a lost thrill or bruit, to a healthcare provider for timely diagnosis and management, which helps preserve its long-term functionality.