Comparative study between 1-way and 2-way coupled fluid-structure interaction in numerical simulation of aortic arch aneurysms.

Hemodynamic forces are related to pathological variations of the cardiovascular system, and numerical simulations for fluid-structure interaction have been systematically used to analyze the behavior of blood flow and the arterial wall in aortic aneurysms. This paper proposes a comparative analysis of 1-way and 2-way coupled fluid-structure interaction for aortic arch aneurysm. The coupling models of fluid-structure interaction were conducted using 3D geometry of the thoracic aorta from computed tomography. Hyperelastic anisotropic properties were estimated for the Holzapfel arterial wall model. The rheological behavior of the blood was modeled by the Carreau-Yasuda model. The results showed that the 1-way approach tends to underestimate von Mises stress, displacement, and strain over the entire cardiac cycle, compared to the 2-way approach. In contrast, the behavior of the variables of flow field, velocity, wall shear stress, and Reynolds number when coupled by the 1-way model was overestimated at the systolic moment and tends to be equal at the diastolic moment. The quantitative differences found, especially during the systole, suggest the use of 2-way coupling in numerical simulations of aortic arch aneurysms due to the hyperelastic nature of the arterial wall, which leads to a strong iteration between the fluid and the arterial wall.

Influence of hemodialysis blood flow rate on the thrombogenic potential in patients with central venous catheters.

In this study we apply methods to determine the tendency for thrombus formation in different central venous catheters (CVC) models associated with flow 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 flow 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 flow rate independent of the type of CVC. This study evidenced that the higher the blood flow rate used in the 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 flow through the CVC arterial lumen presents a proportionally larger thrombogenic potential when compared to the blood flow that leaves the vein towards the atrium. This finding may have consequences for clinical practice, since there is no specific flow 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 flow rate can possibly offer.

Hemodialysis catheter thrombi: visualization and quantification of microstructures and cellular composition.

PURPOSE: Despite the increasing use of central venous catheters (CVC) for hemodialysis in clinical practice, the role of CVC in thrombus development is poorly understood. This work aims at defining new methods and protocols for assessing the micromorphology and composition of thrombi formed into tunneled and non-tunneled hemodialysis CVC removed from patients. 
 METHODS: Twenty-nine CVCs were collected and the microscopic features of intra-luminal thrombi were quantified by scanning electron microscopy (SEM) and visualized by two photon laser scanning microscopy (TPLSM). 
 RESULTS: SEM quantification showed that fibrin was the most abundant structure in CVC thrombi. Specifically, the median micromorphologic composition of the surface layer resulted in: 42.6% of fibrin plaque, 16.3% of fibrin network, 0.4% of fibrin fibers, 9.3% of platelets, 10.3% of erythrocytes and 1.7% of white blood cells. TPLSM showed that sub-surface layers were instead composed by smaller amounts of fibrin and platelets and higher amounts of blood cells.
 CONCLUSIONS: Integration of SEM and TPLSM was found to be an excellent tool for characterizing thrombi in hemodialysis CVC removed from patients. Protocols and techniques presented here may be useful in the development and testing of new strategies for limiting thrombus formation on vascular access because of CVC.

Infecções hospitalares e resistência microbiana em Unidade de Cuidados Intensivos de um Hospital Universitário / Nosocomial infections and resistance microbian in Intensive Care Unit of a University Hospital: an epidemiological study

In the last decades it has been observed an increase in frequency on nosocomial infections by resistant microorganisms, especially in Intensive Care Units (ICU). This study aimed to determine main sites of nosocomial infections and prevalence of multidrug resistant microorganisms. An epidemiological and descriptive study was developed in an adult ICU of a University Hospital of Belo Horizonte, Minas Gerais, from January to December, 2004. Among the most prevalent nosocomial infections were pneumonia, urinary tract infections, and bloodstream infections. Among the resistant microorganisms prevailed Pseudomonas aeruginosa, Acinetobacter baumanii, MRSA, Klebsiella, Enterobacteriaceas and Serratia. As this study is still going on, we expect to determine temporal trends for resistant microorganisms related to nosocomial infections main sites.

Nas últimas décadas tem-se observado o aumento da freqüência das infecções hospitalares (IH) por microrganismos resistentes. Essa realidade é ainda mais evidente em Unidades de Tratamento Intensivo (UTI). Objetivou-se nesse estudo determinar os principais sítios de ocorrência das IH e a prevalência dos microrganismos multirresistentes, nesta unidade. Tratou-se de um estudo epidemiológico, descritivo, desenvolvido na UTI adulto de um Hospital Universitário de Belo Horizonte, Minas Gerais no período de janeiro a dezembro de 2004. Dentre as infecções hospitalares mais prevalentes apresentadas verificou-se que a pneumonia, infecção do trato urinário e da corrente sangüínea foram respectivamente as mais importantes. Na prevalência do microrganismo resistente destacaram a Pseudomonas aeruginosa, Acinetobacter baumanii, MRSA, Klebsiella, Enterobacteriáceas e Serratia. Sendo este um projeto em continuidade espera-se determinar em um período maior a tendência temporal dos microrganismos resistentes correlacionados aos principais sítios de IH.

A percepção da equipe multiprofissional sobre a Comissão de Controle de Infecção Hospitalar / The perception of the healthcare workers about the Hospital Infection Control Committee: an exploratory study

Introduction:The actions of the Infection Hospital Control Comitte (HICC) according to federal regulations 2616/98, are based essentially on the surveillance epidemiologic that makes possible the definition of guidelines?s prevention and control infection. However a high unrest for the health care workers refer the fact that during the health care they haven't understood that the infection control is an ineherent aspect in their practice because of the risk in manipulation of organic matter, secretions and excretions, in addition to contact with microorganisms disseminated by differents route of transmission.Objective: to identify the perception of the healthcare workers team about the performance of Infection Hospital Control Committee (HICC). Methods: This is a descriptive study, completed in a hospital university of Belo Horizonte. A questionnaire was applied to 86 professionals (nurses, physicians and physiotherapists). Results: It was found that 88% of the professionals had knowledge of the meaning of the acronym HICC, 64% of them could identify a case of hospital infection, however just 48,8% had knowledge about the identification criterion of the resistant microorganisms. The lack of knowledge and commitment were the main cause for the low or not adhesion of control measures for hospital infection. In relation to the professional's perception of the HICC, the majority considers it actively participative. Conclusion: this study has important contributions for the reflections of the practices of the healthcare workers team, as well as, for the HICCs think about yours strategic of the training and involvement with the hospital community.

Introdução: As ações das Comissões de Controle de Infecção Hospitalar, de acordo com a portaria 2.616/98, fundamentam-se essencialmente na vigilância epidemiológica que possibilita a definição de diretrizes de prevenção e controle de infecções. Apesar disso,uma grande inquietação para os profissionais, refere-se ao fato de que estes, durante a realização da assistência em saúde não têm entendido que o controle de infecções é um aspecto inerente à sua prática,devido aos riscos na manipulação de matéria orgânica,secreções e excreções,além do contato com microrganismos disseminados por diferentes vias de transmissão. Objetivo: conhecer a percepção da equipe multiprofissional a respeito da atuação da Comissão de Controle de Infecção Hospitalar (CCIH). Método: Realizou-se um estudo descritivo, em um hospital universitário de Belo Horizonte. Utilizou-se um questionário aplicado a 86 profissionais (enfermagem, médicos e fisioterapeutas). Resultados: Verificou-se que 88% dos profissionais conheciam o significado da sigla CCIH, 64% souberam identificar um caso de Infecção hospitalar porém, apenas 48,8% tinham conhecimento sobre os critérios de identificação de microrganismos resistentes. Para a baixa ou não-adesão às medidas de controle das infecções hospitalares, a falta de conhecimento e de compromisso foram os principais motivos citados. Em relação à percepção dos profissionais sobre a CCIH, a maioria a considerou atuante. Conclusão: Acredita-se que este estudo apresenta importantes contribuições para a reflexão, tanto das práticas da equipe multiprofissional como também para as CCIHs de repensarem suas estratégias de treinamento e envolvimento junto à comunidade hospitalar.