Hemodialysis is a treatment for individuals living with kidney failure, a condition where the kidneys can no longer effectively filter waste products from the blood. This process involves diverting blood from the patient’s body through an external filter and then returning the cleansed blood. A specialized point of entry into the bloodstream, known as vascular access, serves as the direct connection for this filtration. The reliability and integrity of this access directly influence the quality and effectiveness of the dialysis procedure.
Why Vascular Access is Essential
Vascular access is essential for hemodialysis because the procedure requires a substantial volume of blood to be processed efficiently. Hemodialysis machines need to draw and return blood at high flow rates, typically between 300 to 500 milliliters per minute, to adequately filter waste products. Regular peripheral veins are smaller and less resilient, unable to sustain this repeated high-volume access or withstand the pressure without damage. Dedicated vascular access is designed to handle these demands, ensuring effective dialysis and patient safety.
Types of Hemodialysis Access
The preferred and most durable vascular access for hemodialysis is the arteriovenous (AV) fistula. An AV fistula is created surgically by connecting an artery directly to a vein, usually in the arm. This connection causes the vein to enlarge and strengthen over several weeks or months, a process called maturation, making it suitable for repeated needle insertions during dialysis. AV fistulas are favored due to their lower rates of infection and clotting, offering the longest survival among access types.
When an AV fistula is not feasible due to unsuitable veins, an arteriovenous (AV) graft may be created. An AV graft uses a synthetic tube, often made of polytetrafluoroethylene, to connect an artery to a vein. This prosthetic tube is placed subcutaneously, allowing for quicker use than a fistula, typically within two to three weeks after surgery. While grafts provide a reliable access point, they carry a higher risk of infection and clotting compared to AV fistulas.
A central venous catheter (CVC) provides immediate access and is often used for temporary or emergency hemodialysis. This involves inserting a flexible tube into a large vein, commonly in the neck (internal jugular), chest (subclavian), or groin (femoral). CVCs are considered a short-term solution due to their highest risk of complications, including infection and blood clots. The subclavian vein is less preferred due to a higher risk of thrombosis compared to the internal jugular vein.
Living With and Caring for Your Access
Maintaining vascular access health involves specific daily care routines. Keep the access site clean by washing it daily with soap and water, ensuring it remains dry. Avoid wearing tight clothing, jewelry, or anything that could constrict blood flow or apply pressure to the arm with the access.
Prevent any medical procedures on the access limb that could compromise its function. Blood pressure cuffs should never be placed on the arm with vascular access, nor should blood be drawn from that arm. Regularly check the access for a “thrill” (a gentle vibration) or a “bruit” (a whooshing sound heard with a stethoscope) to confirm proper blood flow. The absence or change in these sensations warrants immediate medical attention. Protect the access from injury, such as bumps or cuts.
Potential Complications
Despite careful management, vascular access can develop complications requiring prompt medical attention. Infection is common, often indicated by redness, swelling, warmth, pain at the access site, a pimple-like lesion, or fever. Infections, particularly with catheters, are a significant concern.
Clotting, also known as thrombosis, occurs when blood coagulates inside the access, blocking blood flow. Signs include a loss of the thrill or bruit, swelling in the limb, or a noticeable coolness of the skin. This condition requires immediate medical evaluation to restore blood flow and prevent inadequate dialysis.
Stenosis, or narrowing of the blood vessel, can also occur, particularly in the outflow tract of fistulas and grafts. This narrowing impedes blood flow and can lead to symptoms like elevated venous pressure during dialysis or arm swelling. Less frequently, an aneurysm or pseudoaneurysm may develop, appearing as a bulging or swelling near the access site. “Steal syndrome” is a complication where the access diverts too much blood from the hand or foot, causing the extremity to become cold, numb, or painful due to reduced blood supply.