[High-flow fistula: a problem not easy to handle].

High-output cardiac failure is a well-known phenomenon of high-flow fistula in hemodialysis patients. The definition of "high flow" is varied and almost always connected to proximal arteriovenous fistulas (AVF). High flow access is a condition in which hemodynamics is affected by a greater rate of blood flow required for hemodialysis and this can compromise circulatory dynamics, particularly in the elderly in the context of pre-existing heart disease. High access flow is associated with complications like high output heart failure, pulmonary hypertension, massively dilated fistula, central vein stenosis, dialysis associated steal syndrome or distal hypoperfusion ischemic syndrome. Although there is no single agreement about the values of AVF flow volume, nor about the definition of high-flow AVF, there is no doubt that AVF flow should be considered too high if signs of cardiac failure develop. The exact threshold for defining high flow access has not been validated or universally accepted by the guidelines, although a vascular access flow rate of 1 to 1.5 l/min has been suggested. Moreover, even lower values may be indicative of relatively excessive blood flow, depending on the patient's condition. The pathophysiology contributing to this disease process is the shunting of blood from the high-resistance arterial system into the lower resistance venous system, increasing the venous return up to cardiac failure. Accurate and well-timed diagnosis of high flow arteriovenous hemodynamics by monitoring of blood flow of fistula and cardiac function is required in order to stop this process prior to cardiac failure. We present two cases of patients with high flow arteriovenous fistula with a review of the literature.

[Evaluation via ecocolordoppler before creating a vascular access for hemodyalisis: a monocentric experience].

The use of a preoperative echocolordoppler improves the clinical evaluation because provides anatomical and hemodynamic information that make it an important tool in planning vascular access strategy. The preoperative ultrasound study of the vessels can significantly reduce the failure rate and the incidence of complications of vascular access. We describe the experience of our center, lasting 10-year, where the ultrasound assessment was performed in all patients before the creation of vascular access. Indeed, ultrasound reduces the rate of fistula failure and increases the utilization of fistula, allowing proper selection of vessels. In addition, the presence of the vascular access team has allowed us to achieve quite satisfactory results.

[Clinical, ultrasound and treatment of aneurysms and pseudoaneurysms in hemodialysis vascular access]. / Clinica, ecografia e trattamento degli aneurismi e pseudoaneurismi nell'accesso vascolare dell'emodializzato.

Aneurysms (AN) and pseudoaneurysms are among the complications of vascular access. AN is a focal area of expansion, concentric or eccentric, with the wall consistency the same as all elements of the vessel wall (intima, media and adventitia). Pseudoaneurysm, or false aneurysm, is a blood harvesting without vascular wall, it is characterized by a reactive capsule of connective tissue that delimits it. The K/DOQI guidelines recommend a regular program of monitoring and surveillance of the vascular access. Color-Doppler ultrasound is considered a valuable tool in the preoperative evaluation and in the follow-up. The echo-color-Doppler surveillance plays an important role in diagnosis of aneurysm. It allows monitoring the evolution of the aneurysm, studying vessels walls, thickened because of intimal hyperplasia and to identify the presence of thrombotic material and/or calcification of the wall. Early identification of complications and the adoption of corrective measures will extend the life of the vascular access, with benefit for the patient. Moreover, it will reduce health care costs.