Computational Fluid Dynamic Analysis of the Hemodialysis Plastic Cannula

The jet of fluid returning to the patient through a hemodialysis venous needle has previously been reported as a potential source of endothelial damage which can lead to intimal hyperplasia (IH) in arteriovenous fistulae (AVF). Metal needles are the current standard practice for accessing the vascular system in hemodialysis. However, plastic cannulae have been used in Japan for 30 years. This study utilized computational fluid dynamics to analyze the hemodynamics of blood exiting a plastic cannula and determined the optimal placement and blood flow rate. Transient simulations were run using a 15G Argyle Safety Fistula Cannula with Anti-Reflux Valve inserted into an idealized cephalic vein. The cannula tip was fixed at three different locations within the vein (upper third, middle, and lower third) with blood flow rates of 200 mL/min, 300 mL/min, and 400 mL/min imposed. The high degree of jet break down immediately after exiting the cannula was attributed to the staggered side hole arrangement, position of the cannula in the vein, and the imposed blood flow rate. Elevated levels of wall shear stress which may lead to IH were identified at the site of jet impingement on the vein floor as well as regions of high residency time. The risk of IH may be minimized by enhancing the breakdown of the jet through the use of optimal blood flow rates between 300 and 400 mL/min and ensuring the cannula tip is placed away from the walls of the vein.