[Technique and results of duplex-Doppler for non-stenosing complications of vascular access for chronic hemodialysis: ischemia, steal, high flow rate, aneurysm]

Abstract

Two factors increasing flow rate in arteriovenous fisulae (AVF) with the subsequent risk for cardiac function, are the site of the access and time since its creation. Cubital AVF and bypasses are less often involved. Mean flow rate in a distal fistula is 465 +/- 250 ml/min. For proximal fistulae, mean flow rate is 750 +/- 309 ml/min. Flow rate is measured by pulsed duplex-Doppler of the humeral artery or the axillary artery. If high flow rate is poorly tolerated, careful assessment should provide an orientation concerning appropriate correction: ligature of the proximal radial artery to limit arterial inflow to the AVF which is then comes solely from retrograde flow from the radial artery via the palmar arcades and the cubital artery; distal prolongation by radial bypass or transposition after checking the state of the forearm arteries. Vascular steal can lead to ischemia, which is greater for high flow proximal fistulae, with the risk of aggravating pre-existing arteritis. Continuous color-Doppler exploration of the distal vessels, with the fistulae open and closed with compression, is primordial to establish the positive diagnosis and the appropriate therapeutic approach. Flow rate must be determined accurately. If low flow rate is associated with signs of ischemia, angioplastic or surgical revascularisation may be required for identified and accessible areas of stenosis. If the flow rate is too high, reduction may be effective. If the distal Doppler signal is normal or minimally perturbed with the open AVF, the fistula may be the cause of the ischemia. If no flow can be detected when the AVF is closed, the distal artery is involved and may have to be closed. Venous ischemia is much more uncommon and may be caused by venous stenosis downstream from the fistula. Diffuse venous ectasia may result from a downstream obstruction due to stenosis or thrombosis, or to excessive flow. In the event of a false aneurysm, a pulsitile hematoma is visualized by color Doppler with one or more spurts, associated or not with images of mural thrombosis. Deterioration of the vessel walls at the point of puncture can lead to intra-capsular false aneurysm.