Complications of Arteriovenous Fistulas for Hemodialysis
The quality of vascular access for HD should be suitable for repeated puncture and allow a high blood flow rate for high-efficiency dialysis with minimal complications. The dialysis staff must be well versed in manipulation of the AVF, with only minimal need for corrective interventions. Fulfilment of these conditions reduces the risk of turbulence and endothelium injury, which, in turn, minimizes the potential for stenosis.
The most important complications of fistula for HD are lymphedema, infection, aneurysm, stenosis, congestive heart failure, steal syndrome, ischemic neuropathy and thrombosis. The most common cause of vascular access failure is neointimal hyperplasia.
It is important to gain information about early clinical symptoms of AVF dysfunction in order to prevent and adequately treat potential complications.
Most important AV fistula complications
Surgical complications of AV fistula
The choice of operative technique for anastomosis has its own characteristics and is a very important stage towards avoiding certain surgical complications.
For example, end-to-end anastomosis requires a formidable surgical technique. Inadequate surgical technique can lead to ischemia of the distal extremities, especially in the elderly and patients with diabetes mellitus. However, while side-to-side anastomosis is technically easier and can be done if the blood vessels are close to each other, it should be noted that this type of anastomosis may lead to the development of venous hypertension.
Currently, the most acceptable option is end-to-side anastomosis.
In order to reduce the risk of turbulence and endothelium injury which minimizes the potential for stenosis, surgeons should avoid the following: performing an acute angle, longitudinally rotating the veins, or changing their anatomical position.
Immediately after surgery, hemorrhage, low venous flow or hematoma may occur. Later complications may include infections, the development of an aneurysm and/or false aneurysm, fistula vein stenosis, congestive heart failure, steal syndrome, ischemic neuropathy and thrombosis.
Infection accounts for 20% of all AVF complications, which is ten times lower than the rate of infection of AVG. Most AVF infections involve perivascular cellulitis, which manifests as localized erythema and edema and is usually easily treated. Much more serious are infections associated with anatomical abnormalities, such as aneurysms, hematomas or abscesses, which require surgical excision and drainage.
AVF infections are very rare and in most cases respond well to antibiotic treatment administered for 4–6 consecutive weeks.
An aneurysm is a pathological enlargement of the blood vessel wall resulting from repetitive puncture. Surgical intervention is recommended when there is risk of perforation and ulceration, if there are elements of bleeding or if there is limited space for puncture because of the size of the aneurysm.
Generally defined as an abnormal narrowing in a blood vessel. KDOQI guidelines define significant stenosis of the vessel lumen as a reduction of over 50%. Clinical suspicion of stenosis is confirmed by the presence of several factors: reduced quality of dialysis, problems with puncture such as prolonged bleeding after AVF puncture, pain in the area of the fistula or increased venous pressure.
Treatment involves balloon dilatation of the stenosis, stent implantation or surgical revision.
A developed AVF can cause reduced blood flow distal to the arteriovenous anastomosis, which leads to hypoxia, ischemia and necrosis. The risk of ischemia and the emergence of this syndrome, known in the literature as the steal syndrome, are especially high in diabetics and elderly people.
Low resistance in the system of fistula veins and retrograde flow in the area of the palmar arch jeopardize adequate perfusion of the hands.
In general, for the occurrence of ischemia in the hand with a fistula, certain conditions are required, mainly involving reduced blood flow through the arterial system due to arterial occlusive disease.
Data in the literature suggest that symptomatic ischemia develops in 10–25% of patients with brachiocephalic and brachiobasilic vascular access, 4–6% of which at the level of the forearm and 1–2% at the radiocephalic level.
As the treatment of this condition is difficult, attention must be focused on prevention.
Thrombosis is a crucial cause of loss of function of an AVF. It usually occurs near a stenosis, in the area of an anastomosis or fistula vein. The risk of thrombosis increases with the degree of stenosis.
Most studies indicate disturbances of platelet adhesion, thus explaining the tendency towards increased bleeding. It is believed that HD platelets are activated by adhesion to the extracellular circulatory system and the turbulence in blood flow generated by the vascular access.
Significant studies indicate that clopidrogel reduced the frequency of early thrombosis of new AVFs, and did not increase bleeding events during a 6-week administration period. Maintenance of patency is necessary for fistula maturation, which means that prevention of early thrombosis would be associated with a higher rate of fistula maturation.
An important cause of complications in HD patients is an increased thrombotic tendency.
The most common cause of vascular access thrombosis is venous neointimal proliferation, characterized by the proliferation of smooth muscle cells. This causes vascular stenosis, leading to fistula thrombosis.
A functional AVF is a major determinant of successful HD; however, AVFs may be a risk factor for hospitalization in dialysis patients. Knowledge about the potential complications of AVFs should contribute to their timely detection and allow measures to be taken that might prevent deleterious consequences that range from loss of vascular access to serious morbidity, and may ultimately be fatal. Therefore, AVF care should be a priority not only for patients but also for the entire professional team involved in the treatment of dialysis patients.
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Full article: https://www.ncbi.nlm.nih.gov/pubmed/23128647