Section 12 Vascular Access for Hemodialysis - American ...

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Section 12. Vascular Access for Hemodialysis Figure 12.1. Examples of various configurations for AV fistula anastomoses: (a) normal artery-vein relationship, (b) end-to-end anastomosis, (c) end-vein to side-artery anastomosis, (d) side-to-side anastomosis, (e) side-vein to end-artery anastomosis, (f) side-to-side converted to end-to-end anastomosis. C. Placement in order of priority. 1. A wrist (radial-cephalic) primary fistula (see Figure 12.2). 2. An elbow (brachial-cephalic) primary fistula. 3. An upper arm (brachial-basilic) fistula with vein transposition. vein artery Figure 12.2. Preferred site for fistula. Actual site may vary depending on patient. Used with permission from Arrow International Inc. D. Classification of AVFs. The traditional AVF (such as the radial-cephalic or brachial-cephalic) is created with just the construction of the AV anastomosis — a one-step procedure, sometimes known as a primary fistula. With the increased impetus to give priority to AVF creation, more innovative surgical techniques are being used to superficialize the outflow vein such as transposition (surgically dissecting out and tunneling in a superficial, accessible area of limb) of the vein or surgical removal of the tissue between the skin and the vein (Roberts, 2005). AVFs with vein transposition are frequently created with two separate procedures to allow for arterialization of the vein prior to superficialization. E. Indication for AVF creation. A fistula should be placed at least 6 months prior to the anticipated start of hemodialysis treatments. This timing allows for access evaluation and additional time for revision to ensure a working, fully functional fistula is available at initiation of dialysis (NKF KDOQI, 2006, CPG 1). Patients should be considered for construction of a fistula after failure of every dialysis AV access. In the patient performing PD, who is manifesting signs of modality failure, the decision to create a backup fistula should be individualized by periodically reassessing need (NKF KDOQI, 2006, CPG 2). 742 Core Curriculum for Nephrology Nursing, Fifth Edition © American Nephrology Nurses’ Association 2008
Chapter 59. Vascular Access Type and Site of Placement F. Advantages of AVF accesses. 1. Have the lowest rate of thrombosis and require the fewest interventions, providing longer survival of the access (Huber et al., 2003; Pisoni et al., 2002). 2. Have lower rates of infection than grafts (which, in turn, are less prone to infection than percutaneous catheters and subcutaneous port catheter systems). 3. Cost of implantation and access maintenance are the lowest long-term. 4. Are associated with increased survival (Dhingra et al., 2001) and lower hospitalization rates. 5. Avoid the complications associated with the venous anastomosis in AVGs. 6. Avoid potential for allergic response to synthetic materials. 7. Outflow veins are autogenous tissue which seals and heals after cannulation. Synthetic grafts only seal by means of a fibrin plug. 8. Can utilize the buttonhole cannulation technique. G. Disadvantages of AVF accesses. 1. The vein may fail to enlarge or increase wall thickness (i.e., fail to mature). This may be caused by inadequate inflow or the presence of collateral or accessory veins that divert both volume and pressure from the intended outflow vein. 2. AVFs have comparatively long maturation times. Weeks to months must elapse following creation of these fistulae before they can be used. If the access has not been created several weeks in advance of the anticipated need for dialysis, an alternative method of vascular access must be used while the fistula matures. 3. In some individuals, the vein may be more difficult to cannulate than an AVG. 4. AVF creation and cannulation require different skill sets than for AVGs. Proficiency in one type of access does not assure proficiency in the other. 5. Thrombosed AVF may be more difficult in which to restore flow. 6. The enlarged vein may be visible, especially in the forearm and perceived as cosmetically unattractive by some individuals. 7. A hypertrophied outflow vein may significantly increase cardiac output (in turn increasing cardiopulmonary recirculation), and myocardial load and may cause steal syndrome in patients with compromised peripheral vasculature. H. Complications of AVFs (KDOQI, 2006, CPG 5). 1. Nonmaturing outflow vein and early failure. Primary nondevelopment of the outflow vein may be secondary to: a. Insufficient vasculature caused by poor arterial flow and/or small vein size. Signs and symptoms. (1) Minimal increase in vein size and bruit limited to anastomosis area. (2) Absence of palpable thrill and bruit by auscultation along the outflow vein. b. Treatment is surgical revision if possible. 2. Disturbances in flow dynamics that are usually caused by venous stenosis (abnormal narrowing of the lumen of the vessel as a result of injury to the wall causing intimal hyperplasia). Related problems include: a. Venous hypertension: engorgement of vessels distal to anastomosis when resistance to flow is greater in proximal veins due to venous stenosis (Schanzer, 2002). b. Sore thumb syndrome: engorgement of thumb veins with sometimes painful throbbing or pulsating of distal veins and edema of thumb that may extend to entire hand; cyanotic nail bed with potential for serous oozing if obstruction of venous capillary drainage continues (White, 2006). c. Increased venous return can cause arm, breast, neck, chest, and face swelling if stenosis develops in the central vessels. 3. Accessory veins: arterial flow through multiple outflow veins prevents the arterialization of a single outflow vein and therefore the development of a functional fistula; thrill and bruit are present but appropriate vein development is absent. To detect the presence of an accessory vein, occlude the main outflow vein with finger pressure sequentially along the vein. Note the character of the flow with the occlusion. If there is no accessory, the flow will become an augmented pulse. If an accessory vein is present between the anastomosis and the occlusion point, the thrill will continue. 4. Medical diagnostics and treatment. a. Doppler ultrasound or fistulogram/venogram to measure flow and detect stenosis. Treatment for hemodynamically significant stenosis is balloon angioplasty. b. Treatment for venous hypertension is arm elevation above the level of the heart. c. Treatment for accessory veins is surgical ligation or percutaneous coil ablation (coils Core Curriculum for Nephrology Nursing, Fifth Edition © American Nephrology Nurses’ Association 2008 743
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