Análise numérica das alterações hemodinâmicas decorrentes da inserção do cateter venoso central e suas influências no processo de formação trombos

Abstract

The use of a central venous catheter for prolonged periods leads to thrombus generation that can cause several complications, such as thrombosis at the vascular access site, emboli, deep venous thrombosis, and possible development of cardiac ischemia. Several factors contribute to thrombus generation, but they are not fully understood yet, in the literature. This thesis aimed to evaluate the process of thrombus formation in a central venous catheter caused by the hemodynamic influence of the catheter, using numerical simulation of the flow. In order to experimentally validate this numerical model, a new fabrication protocol of patient-specific experimental models of blood vessels was developed. Which is capable of manufacture models that simultaneously have a defined wall thickness and high geometric complexity. Using this experimental model, a new approach for in vitro validation of computational fluid dynamics simulations was presented, which consisted of using a state-of-the-art framework for flow measurement using ultrasound techniques. Simulations were performed with fluid-structure interaction, transients flow, using a non-Newtonian model for blood, and a k-ω SST turbulence model for cases of the internal jugular vein without the presence of the catheter, and with and without flow in the inserted catheter. The results showed a high correlation (r = 0.996) between regions of high wall shear stresses and regions of incidence of thrombus found in the literature. The central venous catheter changed the hemodynamics in the vein creating zones of recirculation at low flow rate, in addition to non-physiological shear stresses (>100 Pa) capable of activating platelets and increasing platelet aggregation. Moreover, the results give some insights of how the hemodynamic changes caused by the catheter insertion influence the process of thrombus formation and growth.