Thabata Coaglio Lucas

Blood flow in hemodialysis catheters: a numerical simulation and microscopic analysis of in vivo-formed fibrin.

Although catheters with side holes allow high flow rate during hemodialysis, they also induce flow disturbances and create a critical hemodynamic environment that can favor fibrin deposition and thrombus formation. This study compared the blood flow and analyzed the influence of shear stress and shear rate in fibrin deposition and thrombus formation in nontunneled hemodialysis catheters with unobstructed side holes (unobstructed device) or with some side holes obstructed by blood thrombi (obstructed device). Computational fluid dynamics (CFD) was performed to simulate realistic blood flow under laminar and turbulent conditions. The results from the numerical simulations were compared with the fibrin distribution and thrombus architecture data obtained from scanning electron microscopy (SEM) and two photons laser scanning microscopy (TPLSM) on human thrombus formed in catheters removed from patients. CFD showed that regions of flow eddies and separation were mainly found in the venous holes region. TPLSM characterization of thrombi and fibrin structure in patient samples showed fibrin formations in accordance with simulated flux dynamics. Under laminar flow conditions, the wall shear stress close to border holes increased from 87.3±0.2 Pa in the unobstructed device to 176.2±0.5 Pa in the obstructed one. Under turbulent flow conditions, the shear stress increased by 47% when comparing the obstructed to the unobstructed catheter. The shear rates were generally higher than 5000/s and therefore sufficient to induce fibrin deposition. This findings were supported by SEM data documenting a preferential fibrin arrangement on side hole walls.

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.

Validação do reprocessamento de cateteres cardíacos angiográficos: uma avaliação da funcionalidade e da integridade

The objective of this study was to validate the reprocessing of angiographic cardiac catheters regarding their characteristics of mechanical functionality and the molecular and micro-structural integrity of the polymeric chain.This is an experimental, applied, comparative and controlled study. A simulation set was built for a left coronary angiography in order to simulate mechanical and biological stress in the catheters. Traction tests were performed for the functionality and the integrity was tested through Infrared Spectrometry and Scanning Electronic Microscopy. The study evidenced a tendency to an increase in rigidity at every increment of the reprocessing number (p < 0.05). The changes in the mechanical properties and molecular structures of the polymers were more evident as of the fifth reprocessing. Micrographies revealed an increase in rugosity as of the forth reprocessing. The results of this study may contribute to the elaboration of reprocessing protocols and a systematic surveillance of the reutilization of single use materials, not only due to their economical relevance, but especially from the ethical, legal, biological, functional and care point of view.El objetivo del trabajo fue validar el reprocesamiento de cateteres cardiacos angiograficos en cuanto a sus caracteristicas de funcionalidad mecanica e integridad molecular y microestructural de la cadena de polimeros. Investigacion experimental, aplicada, comparativa y controlada. Se construyo un banco de simulacion de una arteriografia de coronaria izquierda para simular un estres mecanico y biologico en cateteres. Se testeo la funcionalidad por ensayo de traccion y la integridad por Espectroscopia Local Infrarroja y Microscopia Electronica de Barrido. Se evidencio una tendencia al aumento de la rigidez en cada incremento del numero de reprocesamientos (p<0,05). Las modificaciones de las propiedades mecanicas y de las estructuras moleculares de los polimeros fueron mas evidentes a partir del quinto reprocesamiento. Las micrografias revelaron un aumento de rugosidad a partir del cuarto reprocesamiento. Los resultados de este estudio podran contribuir en la elaboracion de protocolos de reprocesamiento y vigilancia sistematica de la reutilizacion de materiales de uso unico, no solo por su relevancia economica, sino tambien, y sobre todo, respecto del punto de vista etico, legal, biologico, funcional y asistencial.

Quantification of fibrin in blood thrombi formed in hemodialysis central venous catheters: a pilot study on 43 CVCs.

Purpose Fibrin deposition and thrombotic occlusion represent a serious cause of access dysfunction in hemodialysis central venous catheters (CVCs). The aim of this work was to define and apply a method for imaging and quantifying fibrin in thrombi formed into the side holes of CVCs. Methods Forty-three CVCs removed from a cohort of dialyzed patients were analyzed in this pilot study. Hematoxylin and eosin and a modified Carstairs staining were applied on permanent thrombus sections. Fluorescence microscopy and image analysis were performed to quantify the fibrin amount. Results Highly fluorescent areas were invariably associated with fibrin by Carstairs method. The deposition of concentric layers of fibrin and erythrocytes was easily identified by fluorescence microscopy, showing growth features of the thrombus. Fibrin amount in diabetic patients was significantly higher than that in nondiabetic patients with median (interquartile range) values of 51% (47-68%) and 44% (30-54%), respectively (p=0.032). No significant difference in fibrin content was found by grouping data according to catheter type, permanence time, insertion site and dialysis vintage. Higher variability in fibrin values was found in thrombi from CVCs removed after 1-15 days compared with 16-60 days. A trend of an increase in fibrin amount in thrombi was noted according to blood platelet count at CVC insertion. Conclusions The analytical method presented here proved to be a rapid and effective way for quantifying fibrin content in thrombi formed on CVCs with potential application in future clinical studies.

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.

Adoption of measures of the precaution in the teaching care practice by health care workers team: perceptions and limitations

It was aimed at knowing the participation of the professionals in training about infections hospitals, cognitives and behavior aspects to adoption of the precaution and a perception regarding the activities that designates the CCIH. It was a descriptive study carried out in a public hospital in the period from july to November 2006. 159 health care workers took part of the study: 59,1% nursing technicians, 18,9% physicians,13,8% nurses, 5,0% nursing auxiliaries and 3,1% physiotherapeutics. It was verified that for 37,7% of the professionals the CCIH promotes training, but 56,6% never took part on them; 90,6% admitted the indication of the handwashing, however only 46,5% had known the type of the EPI to be used in the colonized patient healthcare and just 17% the type of the precaution to be established for this patient. Concerning the activities that designates the CCIH it was distinguished the training of the professionals and the infections control; the non-adoption of precautions among the professional was justified by inadequate training and knowledge lack. This study contributes for redefinition of the training strategies together the healthcare workers team, favouring the attention for precautions recommendations during the care.

Comparison of five methods of extraction of Staphylococcus aureus DNA for molecular detection by PCR

INTRODUCTION Molecular techniques for the detection of pathogens have been shown to be effective diagnostic tools with high sensitivity and short turnaround times. METHODS This study compared five Staphylococcus aureus DNA extraction methods for detection by the polymerase chain reaction. RESULTS The concentration and purity of the extracted DNA showed that the methods did not yield DNA of significant quality. However, most protocols yielded 100% positivity, even with low DNA concentrations. CONCLUSIONS Although one protocol seemed more efficient than the others, PCR was sensitive enough to allow for detection of S. aureus with all the protocols.

Validación del reprocesamiento de catéteres cardíacos angiográficos: una evaluación de la funcionalidad e integridad

The objective of this study was to validate the reprocessing of angiographic cardiac catheters regarding their characteristics of mechanical functionality and the molecular and micro-structural integrity of the polymeric chain.This is an experimental, applied, comparative and controlled study. A simulation set was built for a left coronary angiography in order to simulate mechanical and biological stress in the catheters. Traction tests were performed for the functionality and the integrity was tested through Infrared Spectrometry and Scanning Electronic Microscopy. The study evidenced a tendency to an increase in rigidity at every increment of the reprocessing number (p < 0.05). The changes in the mechanical properties and molecular structures of the polymers were more evident as of the fifth reprocessing. Micrographies revealed an increase in rugosity as of the forth reprocessing. The results of this study may contribute to the elaboration of reprocessing protocols and a systematic surveillance of the reutilization of single use materials, not only due to their economical relevance, but especially from the ethical, legal, biological, functional and care point of view.El objetivo del trabajo fue validar el reprocesamiento de cateteres cardiacos angiograficos en cuanto a sus caracteristicas de funcionalidad mecanica e integridad molecular y microestructural de la cadena de polimeros. Investigacion experimental, aplicada, comparativa y controlada. Se construyo un banco de simulacion de una arteriografia de coronaria izquierda para simular un estres mecanico y biologico en cateteres. Se testeo la funcionalidad por ensayo de traccion y la integridad por Espectroscopia Local Infrarroja y Microscopia Electronica de Barrido. Se evidencio una tendencia al aumento de la rigidez en cada incremento del numero de reprocesamientos (p<0,05). Las modificaciones de las propiedades mecanicas y de las estructuras moleculares de los polimeros fueron mas evidentes a partir del quinto reprocesamiento. Las micrografias revelaron un aumento de rugosidad a partir del cuarto reprocesamiento. Los resultados de este estudio podran contribuir en la elaboracion de protocolos de reprocesamiento y vigilancia sistematica de la reutilizacion de materiales de uso unico, no solo por su relevancia economica, sino tambien, y sobre todo, respecto del punto de vista etico, legal, biologico, funcional y asistencial.

Reprocessing validation of angiographic cardiac catheters: an evaluation of the functionality and integrity

The objective of this study was to validate the reprocessing of angiographic cardiac catheters regarding their characteristics of mechanical functionality and the molecular and micro-structural integrity of the polymeric chain.This is an experimental, applied, comparative and controlled study. A simulation set was built for a left coronary angiography in order to simulate mechanical and biological stress in the catheters. Traction tests were performed for the functionality and the integrity was tested through Infrared Spectrometry and Scanning Electronic Microscopy. The study evidenced a tendency to an increase in rigidity at every increment of the reprocessing number (p < 0.05). The changes in the mechanical properties and molecular structures of the polymers were more evident as of the fifth reprocessing. Micrographies revealed an increase in rugosity as of the forth reprocessing. The results of this study may contribute to the elaboration of reprocessing protocols and a systematic surveillance of the reutilization of single use materials, not only due to their economical relevance, but especially from the ethical, legal, biological, functional and care point of view.El objetivo del trabajo fue validar el reprocesamiento de cateteres cardiacos angiograficos en cuanto a sus caracteristicas de funcionalidad mecanica e integridad molecular y microestructural de la cadena de polimeros. Investigacion experimental, aplicada, comparativa y controlada. Se construyo un banco de simulacion de una arteriografia de coronaria izquierda para simular un estres mecanico y biologico en cateteres. Se testeo la funcionalidad por ensayo de traccion y la integridad por Espectroscopia Local Infrarroja y Microscopia Electronica de Barrido. Se evidencio una tendencia al aumento de la rigidez en cada incremento del numero de reprocesamientos (p<0,05). Las modificaciones de las propiedades mecanicas y de las estructuras moleculares de los polimeros fueron mas evidentes a partir del quinto reprocesamiento. Las micrografias revelaron un aumento de rugosidad a partir del cuarto reprocesamiento. Los resultados de este estudio podran contribuir en la elaboracion de protocolos de reprocesamiento y vigilancia sistematica de la reutilizacion de materiales de uso unico, no solo por su relevancia economica, sino tambien, y sobre todo, respecto del punto de vista etico, legal, biologico, funcional y asistencial.

Reprocessing of single-use dental medical devices:analysis of chemical and physical impairment

The reprocessing of single-use dental-medical device is a common practice in many countries so as to reduce the costs of health care and the volume of waste generated. Changes in physical and chemical and therefore, adverse events involved in reprocessing are the main concerns related to this practice. Although the reprocessing is a common practice, there are few studies that validate and real risk of re-use of single use dental-medical devices. Is an urgent need for further reflection and evaluation of the risk-benefit decision on the reuse of these items. The objective of this study was to discuss changes in the integrity and functionality of the single-use dental-medical device after cycles of reprocessing. It was used a total of 11 studies from database of the Virtual Health Library. The results of this review showed that reprocessing causes changes in physical and impaired functionality of the single-use dental-medical devices that independent of their type or composition. There was a correlation between the amendments and the number of reprocessing cycles. The reprocessing allows the adverse events that are still unknown. It highlights the importance of a joint assessment of changes in integrity and functionality after each reprocessing and the creation of validated protocols that describe the maximum number of reprocessing cycles.