It is optimal for all patients who begin dialysis to have had adequate time to prepare. This preparation includes a physical examination and the ultrasonic mapping of veins and arteries prior to the procedure. Ideally, the patient can start dialysis on an outpatient basis without having to endure the temporary placement of a catheter, avoiding the potential complications outlined.During the physical examination, the physician will first inspect the arms, and will assess veins with and without a tourniquet. An ultrasound machine characterizes the diameter of veins and arteries in several locations in the arm with the goal to find the best vessels for access creation. The goal is to find veins that are superficial and are widely open. Transposition or moving of a vessel may be needed if the vessels are too deep. The vessels must be long enough to support the fistula. Duplex sonography allows one to visualize the blood vessel anatomy and blood flow in the same image. The examination starts with the cephalic veins at the wrist and the radial artery at the wrist. It works up to the basilic and cephalic veins in the upper arm, along with the brachial artery. Using proximal vein compression with a blood pressure cuff inflated to 50 mm Hg for at least two minutes, the vein should dilate.With deep inspiration the venous flow should increase, but if there is venous obstruction in the central veins, there will be no change in the venous blood flow measured in the arms. Venograms may also be necessary if the patient has had a central catheter placed. This is to exclude a central vein occlusion that might impede the flow of blood returning to the heart. An occlusion would increase the pressure in the veins and accelerate stenosis. It would jeopardize the dynamics of blood flow and interfere with the ability to dialyze.The arteries are also evaluated, and the internal diameter of the radio artery must be at least 1.6 mm to 2.5 mm. The artery must increase in flow for an AV Fistula to be successful, and this is challenged by vascular disease, hypertension and diabetes. The arteries can be evaluated by having the patient clench the fist for two minutes then open it. This should double the flow and thus indicate the artery will respond normally when a fistula is created.Properly mapped vessels enable surgeons to properly place the AV fistula, and can give the health team a better idea as to the prognosis of fistula survival. The successful creation of an AV fistula, already mature and ready to use prior to beginning dialysis, depends upon selecting the modality of therapy well into Stage 4, and following through with vessel mapping and the surgical procedure.
I had vein mapping and he (Vascular Surgeon) still created my first fistula on a vein in my left wrist that was too small and never worked. Went back and had the 2nd fistula placed in my upper left arm on a vein that was too deep. He moved it a little closer to the surface during the fistula creating surgery, and although the fistula was strong and was developing nicely under the skin, it never bulged. I'm happy about that now, but if I had to do dialysis and they couldn't hit it I would have been furious! So my opinion is that vein mapping may not always help.