Computational Model of the Arterial and Venous Needle During Hemodialysis

Arteriovenous fistulae (AVF) are the favored choice of vascular access but still have poor long-term success. Hemodynamic parameters play an important role in vascular health and have been linked to the development of intimal hyperplasia (IH), a pathological growth of the blood vessel initiated by injury. This study aimed to investigate the hemodynamics surrounding the arterial needle (AN) and venous needle (VN), using computational fluid dynamics. A range of blood flow rates, needle positions, and needle orientations were examined. Disturbed flows were found around AN tip in both antegrade and retrograde orientations, which result in regions of high residency time on the surface of the vein and may disrupt endothelial function. Conversely, a high speed jet exits the VN, which produced high wall shear stresses (WSSs) at the point of impingement which can damage the endothelium. The secondary flows produced by jet dissipation also resulted in regions of high residency time, which may influence endothelial structure, leading to IH. The use of shallow needle angles, a blood flow rate of approximately 300 ml/min, and placement of the needle tip away from the walls of the vein mitigates this risk.