published_or_final_version / Paediatrics and Adolescent Medicine / Master / Master of Medical Sciences

The events of cardiac surgery combined with moderate hypothermia hemodilution perfusion and postoperative respiratory care provide the stimuli for the alteration of K+ levels in red blood cells, plasma, and urine. The purpose of this study was to measure the deviations from normal potassium ion concentrations in an attempt to understand the physiological processes involved.

For a considerable number of years the problem of revascularizing the myocardium after the development of coronary circulatory deficiency has stirred the imagination of physiologists, clinicians and surgeons. The obstruction in the coronary system brings a reduction in the coronary blood flow which is responsible for the symptoms and deterioration of the myocardial function In hearts otherwise normal or close to a standard normal state.

The coronary heart disease kills more than 350,000 persons/year and it costs $108.9 billion for the United States each year, in spite of significant advancements in clinical care and education for public, cardiovascular diseases (CVD) are leading cause of death and disability to the nation. A cardiovascular disease involves mainly heart or blood vessels (arteries, veins and capillaries) or both, and then mainly occurs in selected regions and affects heart, brain, kidney and peripheral arteries. As a surgical interventions, stent implantation is deployed to cure or ameliorate the disease. However, the high failure rate of stents used in patients with peripheral artery diseases has lead researchers to give special attention towards analyzing stent structure and characteristics. In this research, the mechanical properties of a stent based on the rhombus structure were analyzed and verified by means of analytical and numerical approaches. Theoretical model based on the beam theory were developed and numerical models were used to analyze the response of these structures under various and complex loading conditions. Moreover, the analysis of the stent inflation involves a model with large deformations and large strains, nonlinear material properties need to be considered to accurately capture the deformation process. The maximum stress values were found to occur in localized regions of the stent. These regions were generally found along the inner radii of each of the connected links connecting each of the longitudinal struts. Stress values throughout the whole stent were typically much lower. The peak engineering stress values were found to be less than the material ultimate strength (limit stress 515Mpa), indicating a safe stent design throughout expansion range. Lastly, the rheological behavior of blood can be quantified by non-Newtonian viscosity. Carreau model is introduced and simulates the situation in the artery, then the available shear stress in the model would help to the future analysis in the contact analysis of stent and the artery.