Holding Pressure: AV Fistula/Graft Complications Part 2
Resources: Rutherford Chapters (10th ed.): 174, 175, 177, 178 Prior Holding Pressure episode on AV access creation: https://www.audiblebleeding.com/vsite-hd-access/ The Society for Vascular Surgery: Clinical practice guidelines for the surgical placement and maintenance of arteriovenous hemodialysis access: https://www.jvascsurg.org/article/S0741-5214%2808%2901399-2/fulltext KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update: https://pubmed.ncbi.nlm.nih.gov/32778223/ Venous Hypertension Definition A functioning AV circuit delivers high volume arterial flow towards a stenotic venous segment, causing buildup in pressure and venous hypertension. If there are few or no branching veins between the access and stenosis, thrombosis could occur Etiology The most common etiology is venous stenosis caused by a history of vessel wall trauma by centrally-inserted venous devices such as tunneled and non-tunneled dialysis catheters, central lines, pacemakers, or defibrillator. In a study performed at a large academic medical center1, new hemodynamically significant central venous stenosis was associated with the duration of catheter dependence (26% in patients with CVCs for more than 6 months, versus 11% in patients with CVCs for less than 6 months). PICC lines can directly damage cephalic and basilic veins Venous stenosis can often go undetected until AV access creation occurs Patient Presentation Symptoms of venous insufficiency will be present– most commonly regional edema, in the area of venous stenosis. If there are patent venous branches between the AV anastomosis and the stenotic area, swelling can occur throughout the arm. Pigmentation, induration, dermatosclerosis, and ulceration may also be observed. An extensive collateral network of veins may be visible throughout anterior chest, shoulder, or flank SVC obstruction can result in swelling of the head, neck and shoulders, as well as a feeling of head and neck fullness, airway compromise, and visual problems Normal palpable thrill can be replaced by a strong pulse Dialysis can be complicated by difficulty with needle access, recirculation syndrome, and arm swelling after dialysis sessions. Workup Central vein thrombosis can be hard to detect on ultrasound because clavicle and sternum can block transmission Venography is essential to determine the presence and severity of venous stenosis or occlusion. Prevention The ideal scenario is to avoid central dialysis catheters completely, and this involves evaluating CKD patients and placing AVF or AVG before the need for dialysis arises. If a patient presents placement of an AVF/AVG, it is important to perform venography if a patient has a history of a central venous catheter or clinical signs of venous hypertension. A history of SVC obstruction from any cause can preclude permanent AV access creation in both upper extremities Treatment Endovascular approaches to venous outflow stenosis can be first-line treatment options, due to their minimal risk. They can also be performed at the same time as a diagnostic venogram. Angioplasty alone or with stenting are the endovascular options. In a study by Bakken et al2 that compared primary high-pressure balloon angioplasty versus stenting, primary patency was equivalent between groups, with 30-day rates of 76% for both groups and 12-month rates of 29% for angioplasty and 21% for stenting. Assisted primary patency was also equivalent with a 30-day patency rate of 81% and 12-month rate of 73% for the angioplasty group, 84% at 30 days, and 46% at 12 months for the stenting group. This study, along with others, shows that the major downside of endovascular interventions, whether angioplasty or stenting, often require repeat intervention and have poor long-term patency. For subclavian vein stenosis, angioplasty alone is appropriate due to its anatomical location that can put a stent at risk for extrinsic compression from the first rib and clavicle. Surgical bypass can be performed Possible bypasses include axillary-axillary, axillary-jugular, axillary-right atrial, and axillary-femoral. In these bypasses, the preferred conduits are autogenous saphenous or femoral veins. In cases where the proximal subclavian vein is obstructed, a jugular vein turndown can be performed. In this procedure the distal jugular vein is transected, sewed end-to-side at the distal subclavian vein, effectively acting as a bypass route for that obstructed segment. The Hemoaccess Reliable Outflow (HeRO) Vascular Access Device can be used as a hybrid approach, combining endovascular and open surgical techniques to bypass a central venous occlusion and provide a reliable outflow for dialysis. This device has a PTFE inflow limb that is sewn end-to-side onto the brachial artery. This limb is tunneled subcutaneously and connected to a silicone-coated nitinol outflow catheter that is inserted into a central vein and tracked directly into the right atrium. This effectively bypasses central venous stenoses. In the largest study to date on HeRO access grafts placed in 167 patients,3 HeRO primary and secondary patency was 48.8% and 90.8%, respectively, at 12 months. Interventions to maintain or re-establish patency were required in 71.3% of patients resulting in an intervention rate of 1.5/year. Access-related infections were reported in 4.3% patients. The authors concluded that HeRO device had performed comparably to standard AVGs and had proven superior to tunneled dialysis catheters in terms of patency, intervention, and infection rates. If no treatment options for venous hypertension or outflow obstruction are available, an alternate AV access site can be created, either in the contralateral arm if the SVC is uninvolved, or through placement of femoral AV access or a peritoneal dialysis catheter. Bleeding Access Site Etiology and Risk Factors Bleeding can be caused by high venous pressure after dialysis, pseudoaneurysm rupture, or trauma. Patients with end stage renal disease (ESRD) have a baseline elevated risk of bleeding due to uremia-induced platelet dysfunction and use of systemic anticoagulation within the hemodialysis circuit. Additional risk factors include dialysis through an AV graft, hypertension, longer duration of access use, and compromised integrity of the vascular access due to complications (clotting, infection) or invasive procedures. Dual antiplatelet therapy is also associated with overall bleeding events in ESRD patients. Dialysis patients could be on antiplatelet therapy for management of comorbid cardiovascular risk and/or patency of AV graft Patients with bleeding fistulas often present from their dialysis unit when standard digital pressure at the cannulation site fails to stop the bleeding. This is a very serious condition since most mature fistulas have high blood flow and the patients are at risk for hemorrhagic shock and death. Initial Management The first step of management is to obtain hemostasis. Elevate the limb above the level of the heart and apply firm and directed pressure at the site of bleeding using gauze for at least 30-40 minutes Milosevic et al4 reviewed non-operative management of bleeding fistulas and grafts and found that compared to standard dressings, the use of specialized hemostatic dressings decreased bleeding time at arterial and venous cannulation sites. These hemostatic materials included the IRIS compression bandage and cellulose-based, chitosan-based, poly-N-acetyl glucosamine-based, and thrombin-soaked dressings. There has been a "bottlecap method" described where the hollow side of a bottlecap is pressed on top of the puncture site. Maintaining pressure on the cap will cause the cap to fill with blood and clot, which tamponades the bleeding. The provider can also place a shallow figure-of-8 or purse string stitch just below the skin surface to aid in hemostasis. It is important to avoid placing the suture too deep as this can cause inadvertent fistula ligation. During this process, an assistant applies pressure just proximal and distal to the bleeding site to stop blood flow so the sutures can be placed. If these methods fail to achieve hemostasis, apply a tourniquet proximal to the fistula and tighten it until bleeding stops and the radial pulse is lost. This signifies complete occlusion of arterial inflow to the fistula. Tourniquet use should be limited to 3 hours or less, since limb ischemia beyond this timepoint is associated with permanent neuromuscular damage. Regardless of the method used for initial hemostasis, the patient is at risk for repeat hemorrhage, hematoma formation, vessel stenosis, and thrombosis. They should be evaluated by a vascular surgeon as soon as possible. Definitive Management Definitive management depends on etiology of each case, and there are a variety of interventions that can be pursued (i.e. aneurysmorrhaphy for aneurysmal bleeding) If skin erosion over the conduit is present, it should be assumed that the AV access is infected and emergency intervention should be pursued. A jump graft can be placed through with healthy tissue. A covered stent could be introduced through a separate percutaneous puncture site Finally, coagulopathy can be addressed by administering cryoprecipitate, DDAVP, erythropoietin, estrogen, tranexamic acid. Aneurysms and Pseudoaneurysms Definition and Etiology Aneurysms involve all three layers of the vessel wall and they develop due to hemodynamic changes causing remodeling of the vein wall in an AV fistula. This is necessary for vein maturation, but becomes problematic if the post-anastomotic vein continues to dilate and becomes aneurysmal. Aneurysms can also occur at anastomosis sites due to technical aspects of the surgery. Pseudoaneurysms only involve some layers of the vessel wall caused by repeated puncture for hemodialysis. Both aneurysms and pseudoaneurysms can enlarge due to venous outflow stenosis causing increased intraluminal pressures. Both true aneurysms and pseudoaneurysms can lead to overlying skin erosion and subsequent hemorrhage, pain, AV access dysfunction, and cannulation difficulties. Dialysis cannulation should be avoided at the aneurysmal sites to prevent bleeding complications. Diagnosis They can be diagnosed on ultrasound, which also provide information on flow rates, presence inflow/outflow/stenoses, and vessel diameters. Indications for Treatment Treatment is indicated for aneurysms that are rapidly expanding or ulcerating through the skin surface. These are at high risk for rupture and hemorrhage, which is life-threatening. Treatment is also indicated when the aneurysm occurs at the anastomotic site of the AV fistula, the patient has a cosmetic concern, cannulation becomes difficult, there is concern for infection, or the patient has high-output heart failure that could be exacerbated by high flow through the fistula. Treatment is not indicated in asymptomatic aneurysms, regardless of their size. True aneurysms and pseudoaneurysms are not prone to spontaneous rupture. Treatment Options Aneurysmorrhaphy is the most common treatment. It involves the resection of the aneurysmal vein wall to restore a normal diameter and removal of excess skin. Anastomosis is performed along the lateral wall to prevent issues with cannulation along the suture line. Aneurysm resection with interposition grafting is also possible. If multiple aneurysmal segments require treatment, staging their repairs can allow for continuation of dialysis without needing to place a temporary dialysis catheter. AV access ligation is an appropriate alternative to AV access salvage in certain situations but usually requires excision of the aneurysm/pseudoaneurysm due to the potential to develop thrombophlebitis and the cosmetic appearance of the thrombosed segment. If there is concern for an infected pseudoaneurysm or aneurysm, surgery should include removal of all infected material. References 1. Al-Balas A, Almehmi A, Varma R, Al-Balas H, Allon M. De Novo Central Vein Stenosis in Hemodialysis Patients Following Initial Tunneled Central Vein Catheter Placement. Kidney360. 2022;3(1):99-102. doi:10.34067/KID.0005202021 2. Bakken AM, Protack CD, Saad WE, Lee DE, Waldman DL, Davies MG. Long-term outcomes of primary angioplasty and primary stenting of central venous stenosis in hemodialysis patients. J Vasc Surg. 2007;45(4):776-783. doi:10.1016/j.jvs.2006.12.046 3. Gage SM, Katzman HE, Ross JR, et al. Multi-center Experience of 164 Consecutive Hemodialysis Reliable Outflow [HeRO] Graft Implants for Hemodialysis Treatment. Eur J Vasc Endovasc Surg. 2012;44(1):93-99. doi:10.1016/j.ejvs.2012.04.011 4. Milosevic E, Forster A, Moist L, Rehman F, Thomson B. Non-surgical interventions to control bleeding from arteriovenous fistulas and grafts inside and outside the hemodialysis unit: a scoping review. Clin Kidney J. 2024;17(5):sfae089. doi:10.1093/ckj/sfae089
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