The present study aimed to numerically simulate blood flow within central venous catheters of hemodialysis and its thrombogenic potential. Numerical simulation research performed through the dynamic computational program of fluids. A three-dimensional geometry of right and left internal jugular veins were built, taken from the Visible Human Project®. Catheters with obstructed and unobstructed lateral holes were constructed. For the simulation, we considered the duration of the cardiac cycle of 0.8 s with pulsatile cycle of 75 beats per minute. Shear stress, velocity and pressure increased when the catheter was within the vein and when they were obstructed. At the venous orifice of the catheter that was unobstructed, the velocity increased from 0.99 ± 0.02 m s-1 to 1.79 ± 0.009 m s-1 and the pressure from 1487 ± 0.8 Pa to 3215 ± 0.7 Pa. Blood re-circulation areas have created areas of stagnation of blood flow, making it more susceptible to the development of venous thrombi. This study may contribute to the expansion of multiprofessional partnerships between health professionals and Bioengineering fields in order to study health problems that can be verified through advanced technologies. Such technologies, such as simulation programs, detail possible adverse events based on scientific evidences which often occur silently in patients.

This paper presents for the first time a numerical prediction of the thrombogenic potential by means of partial differential equation in computational fluid dynamics for cardiovascular devices. To quantify the thrombogenic potential was developed the Platelet Lysis Index equation in an Eulerian model. Six different catheter tip models with the results obtained from the literature, however, with Lagrangian approach were compared. Three-dimensional computational fluid dynamics was done with a realistic central venous catheter model. The partial differential equation covers the entire computational domain, allowing the visualization of the regions with the highest platelet activation. In the realistic catheter, the first arterial proximal hole was the region with the highest Platelet Lysis Index and shear rate. Despite all limitations and considerations, the use of the Eulerian model allows a quick numerical comparison of the thrombogenic potential of cardiovascular device, being a useful tool in its design.

The formation of thrombi in medical devices that come into contact with blood is a common cause of increased morbidity and mortality. Prolonged use of central venous catheters (CVCs) may cause high infection rates or compromise CVC patency due to thrombus development. In this study, we sought insights into possible changes in the hemostatic system during prolonged use of inserted CVCs for hemodialysis by assessing platelets by CD62P and CD41a expression and the potential for thrombin generation (TG). This study included patients with chronic renal failure who were undergoing hemodialysis three times a week using a CVC, and healthy subjects as controls. The participants were distributed into three groups: Group 1: clinically and laboratorially healthy individuals matched by sex and age to the patients (controls); Group II: patients who had completed 1 month of CVC insertion; and Group III: the same patients after they had completed 4 months of CVC insertion. Platelet activation analysis and TG evaluation were performed using blood samples obtained through two different accesses, that is, through a peripheral vein and directly from the CVC lumen. The data showed platelet activation and an increase in the generation of thrombin, particularly after 4 months of CVC use. The results also indicated that insertion of the catheter into the blood stream stimulated the intrinsic rather than the extrinsic pathway. Taken together, the data showed a direct relationship between the use of CVCs in hemodialysis patients and a state of hypercoagulability, most likely associated with endothelial damage and the contact of the medical device with blood components such as platelets and coagulation factors.

In this study we apply methods to determine the tendency for thrombus formation in different central venous catheters (CVC) models associated with fl ow rate variation. To calculate the thrombogenic potential, we proposed a new numerical model of the platelet lysis index (PLI) equation. To compare the results of PLI and fl ow rate in different models of catheters, numerical calculations were performed on three different tips of CVC. The results showed that the PLI increases as a power function of the fl ow rate independent of the type of CVC. This study evidenced that the higher the blood fl ow rate used in th e catheter, the greater the potential for thrombus formation. The PLI computed at the catheter outlet presented higher values when compared to the values computed at the vein outlet indicating that the blood fl ow through the CVC arterial lumen presents a proportionally larger thrombogenic potential when compared to the blood fl ow that leaves the vein towards the atrium. This fi nding may have consequences for clinical practice, since there is no specifi c fl ow value recommended in the catheter when the hemodialysis machine is turned on, and with this equation it was possible to demonstrate the thrombogenic potential that the fl ow rate can possibly offer.

No abstract

ABSTRACT. This study describes the development of equipment capable of transporting decellularization fluid through an organ by perfusion to create an in vitro acellular scaffold that maintains the three-dimensional architecture of the organ. The equipment was designed to be compatible with several existing decellularization protocols and can be used to modify the flow rate, perfusion pressure, and temperature in each decellularization protocol as well as the technique of cannulation of the organ in a controlled manner. The device was tested with chicken hearts and efficiently accomplished decellularization using the perfusion method. Further amendments can be made to improve the efficiency of the decellularization of diverse organs. It is expected that this equipment will aid in the characterization and improvement of the decellularization process and may have future applications in the process of recellularization of different organs.Keywords: decellularization; cardiac bioengineering; biomaterials; perfusion process; heart decellularization Desenvolvimento de equipamento para decelularização pelo método de perfusão RESUMO. O presente estudo descreve o desenvolvimento de um equipamento capaz de transportar o fluido de decelularização através do órgão inteiro, por perfusão, para criar uma estrutura acelular in vitro que mantém a arquitetura tridimensional completa do órgão. O equipamento foi concebido ser compatível com vários protocolos de decelularização existentes e pode ser utilizado para modificar a vazão, a pressão e a temperatura de perfusão em cada protocolo, bem como a técnica de canulação do órgão de uma forma controlada. O dispositivo foi testado com corações de galinha e executou eficientemente o protocolo de decelularização, utilizando o método de perfusão. Outras alterações podem ser feitas para melhorar a eficiência da decelularização em diversos órgãos. Espera-se que este equipamento auxilie na caracterização e melhoria do processo de decelularização além de possibilitar futuras aplicações no processo de recelularização de diferentes órgãos.Palavras-chave: decelularização; bioengenharia cardíaca; biomateriais; processo de perfusão; decelularização de coração.

No abstract

No abstract