Browsing by Subject "arteriovenous graft"

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    3D simulation of a viscous flow past a compliant model of arteriovenous-graft annastomosis
    (Elsevier, 2019-03) Bai, Zengding; Zhu, Luoding; Mathematical Sciences, School of Science
    Hemodialysis is a common treatment for end-stage renal-disease patients to manage their renal failure while awaiting kidney transplant. Arteriovenous graft (AVG) is a major vascular access for hemodialysis but often fails due to the thrombosis near the vein-graft anastomosis. Almost all of the existing computational studies involving AVG assume that the vein and graft are rigid. As a first step to include vein/graft flexibility, we consider an ideal vein-AVG anastomosis model and apply the lattice Boltzmann-immersed boundary (LB-IB) framework for fluid-structure-interaction. The framework is extended to the case of non-uniform Lagrangian mesh for complex structure. After verification and validation of the numerical method and its implementation, many simulations are performed to simulate a viscous incompressible flow past the anastomosis model under pulsatile flow condition using various levels of vein elasticity. Our simulation results indicate that vein compliance may lessen flow disturbance and a more compliant vein experiences less wall shear stress (WSS).
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    Life-threatening post-thrombectomy hypotension due to residual complications from a translumbar catheter
    (Oxford University Press, 2010-10) Friedman, Allon N.; Butty, Sabah D.; Department of Medicine, IU School of Medicine
    Translumbar catheters offer an alternative life-saving option in patients without conventional dialysis access, though their use and complication rates are poorly understood. We report the first case in the medical literature of a translumbar catheter inducing a central venous stenosis. This occult sequela converted what is usually a subclinical complication from an arteriovenous graft thrombectomy into a life-threatening one. This unusual clinical presentation highlights the need for clinicians to recognize the potential serious implications of translumbar catheter-induced occult central venous stenosis.
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    Simulation of blood flow past a distal arteriovenous-graft anastomosis at low Reynolds numbers
    (AIP, 2019-09) Bai, Zengding; Zhu, Luoding; Mathematical Sciences, School of Science
    Patients with end-stage renal disease are usually treated by hemodialysis while waiting for a kidney transplant. A common device for vascular access is an arteriovenous graft (AVG). However, AVG failure induced by thrombosis has been plaguing dialysis practice for decades. Current studies indicate that the thrombosis is caused by intimal hyperplasia, which is triggered by the abnormal flows and forces [e.g., wall shear stress (WSS)] in the vein after AVG implant. Due to the high level of complexity, in almost all of the existing works of modeling and simulation of the blood-flow vessel-AVG system, the graft and blood vessel are assumed to be rigid and immobile. Very recently, we have found that the compliance of graft and vein can reduce flow disturbances and lower WSS [Z. Bai and L. Zhu, “Three-dimensional simulation of a viscous flow past a compliant model of arteriovenous-graft anastomosis,” Comput. Fluids 181, 403–415 (2019)]. In this paper, we apply the compliant model to investigate possible effects of several dimensionless parameters (AVG graft-vein diameter ratio Rgv, AVG attaching angle θ, flow Reynolds numbers Re, and native vein speed Vv) on the flow and force fields near the distal AVG anastomosis at low Reynolds numbers (up to several hundreds). Our computational results indicate that the influences of the parameters Rgv, θ, and Re lie largely on the graft and the influence of Vv lies largely on the vein. In any case, the WSS, wall shear stress gradient, and wall normal stress gradient and their averaged values on the graft are significantly greater than those on the vein. ACKNOWLEDGMENTS