Electrokinetic properties of NaCl solution via molecular dynamics simulations with scaled-charge electrolytes.

Scaling ionic charges has become an alternative to polarizable force fields for representing indirect charge transfer effects in molecular simulations. In our work, we apply molecular dynamics simulations to investigate the properties of NaCl aqueous solutions in homogeneous and confined media. We compare classical integer- and scaled-charge force fields for the ions. In the bulk, we validate the force fields by computing equilibrium and transport properties and comparing them with experimental data. Integer-charge ions overestimate dielectric saturation and ionic association. Both force fields present an excess in ion-ion correlation, which leads to a deviation in the ionic conductivity at higher ionic strengths. Negatively charged quartz is used to simulate the confinement effect. Electrostatic interactions dominate counter-ion adsorption. Full-charge ions have stronger and more defined adsorption planes. We obtain the electroosmotic mobility of the solution by combining the shear plane location from non-equilibrium simulations with the ionic distribution from equilibrium simulations. From the Helmholtz-Smoluchowski equation, the zeta potential and the streaming potential coupling coefficient are computed. From an atomic-scale perspective, our molecular dynamics simulations corroborate the hypothesis of maximum packing of the Stern layer, which results in a stable and non-zero zeta potential at high salinity. The scaled-charge model representation of both properties is in excellent qualitative and quantitative agreement with experimental data. With our work, we demonstrate how useful and precise simple scaled-charge models for electrolytes can be to represent complex systems, such as the electrical double layer.

Thermodiffusion of CO2 in Water by Nonequilibrium Molecular Dynamics Simulations.

The components of a fluid mixture may segregate due to the Soret effect, a coupling phenomenon in which mass flux can be induced by a thermal gradient. In this work, we evaluate systematically the thermodiffusion of the CO2-H2O mixture, and the influence of the geothermal gradient on CO2 segregation in deep saline aquifers in CO2 storage. The eHeX method, a nonequilibrium molecular dynamics simulation approach, is judiciously selected to simulate the phenomenon. At 350 K, 400 bar, and CO2 mole fraction of 0.02 (aquifer conditions), CO2 accumulates on the cold side, and the thermal diffusion factor is close to 1 in a number of force fields. The lower the temperature, the higher is the separation and the thermal diffusion factor. In colder regions, water self-association is stronger, whereas the CO2-H2O cross-association and the CO2-CO2 interactions enhance at higher temperatures. Thermodiffusion and gravitational segregation have opposite effects on CO2 segregation. At typical subsurface conditions, the Soret effect is more pronounced than gravity segregation, and CO2 concentrates in the top (colder region). Our work sets the stage to model the effect of electrolytes on CO2 segregation in subsurface aquifers and other areas of interest.

Tratamento de perfuração coronária tipo IV durante intervenção coronária percutânea / Treatment for type 4 coronary perforation during percutaneous coronary intervention

Relatamos o caso de um paciente de 61 anos de idade, hospitalizado por angina instável. Cineangiocoronariografia demonstrou lesão obstrutiva grave no terço médio da artéria descendente anterior. Intervenção coronária percutânea foi realizada com implante de stent. Logo depois da pós-dilatação com cateter-balão, observou-se ruptura coronária, com extravasamento de contraste para o ventrículo esquerdo (perfuração coronária tipo IV). Após reversão parcial da heparina com protamina e insuflação prolongada do cateter-balão com baixa pressão, a ruptura coronária foi controlada, com bom resultado angiográfico final. Ecocardiografia realizada em seguida evidenciou derrame pericárdico mínimo. A evolução clínica foi satisfatória após o procedimento.

We report the case of a 61-year-od male, hospitalized for unstable angina. Coronary angiography showed a severe lesion in the middle third of the left anterior descending coronary artery. Percutaneous coronary intervention was performed with stent implantation. Coronary rupture was observed with contrast spilling to the left ventricle (type IV coronary perforation) immediately after balloon post-dilatation. After partial heparin reversal with protamine and prolonged balloon inflation at low pressure, coronary rupture was controlled, with a good final angiographic result. Subsequent echocardiography showed minimal pericardial effusion. Post-procedure clinical follow-up was satisfactory.

Intervenção coronária percutânea pela via radial: incorporação da técnica e resultados de um centro de formação em cardiologia intervencionista / Percutaneous coronary intervention by radial approach: technique incorporation and outcomes of an interventional cardiology training center

INTRODUÇÃO: A via radial evoluiu na última década para uma abordagem versátil, mostrando resultados equivalentes ou superiores aos da via femoral. Avaliamos a incorporação da técnica radial em um centro formador de cardiologistas intervencionistas, e comparamos seus resultados aos da técnica femoral. MÉTODOS: Estudo observacional, unicêntrico, que incluiu pacientes consecutivos submetidos a intervenção coronária percutânea (ICP) entre 2007 e 2011. A via de acesso foi escolhida pelo residente, em conjunto com o intervencionista responsável pela ICP. Comparamos o desfecho combinado de óbito, infarto do miocárdio (IM) periprocedimento, acidente vascular cerebral isquêmico ou sangramentos maiores entre os dois grupos na fase hospitalar. RESULTADOS: Foram submetidos a ICP 5.545 pacientes, 29,8% pela via radial e 70,2% pela via femoral. A média de idade foi de 60,8 ± 11,7 anos, sendo 68,9% do sexo masculino e 29% portadores de síndromes coronárias agudas. Houve aumento do uso da via radial até 2010, e estabilização no ano subsequente (11,8% em 2008, 26,1% em 2009, 45,1% em 2010 e 42,6% em 2011). Os pacientes que utilizaram a via radial tinham perfil tanto clínico como angiográfico menos complexo. Não houve diferenças nos desfechos combinados (5% vs. 5,9%; P = 0,18), no óbito (0,1% vs. 0,8%; P = 0,71), no acidente vascular cerebral (0,06% vs. 0,03%; P = 0,53) ou no IM periprocedimento (4,5% vs. 3,8%; P = 0,27). Contudo, menor incidência de sangramentos maiores (0,4% vs. 1,3%; P < 0,01) e de complicações vasculares (0,5% vs. 2,2%; P < 0,01) foi observada com a via radial. CONCLUSÕES: Em nosso centro formador de cardiologistas intervencionistas, a ICP pela via radial foi rapidamente incorporada, e trouxe, para pacientes selecionados, resultados equivalentes aos da via femoral, com redução dos índices de sangramentos maiores e de complicações vasculares.

BACKGROUND: The radial artery access has evolved into a flexible approach in the last decade, showing similar or superior results when compared to the femoral approach. We assessed the incorporation of the radial artery access in a training center for interventional cardiologists and compared the results to those of the femoral artery access. METHODS: Observational, single-center study, including consecutive patients undergoing percutaneous coronary intervention (PCI) between 2007 and 2011. The access route was chosen by the resident along with the interventionist responsible for PCI. We compared the composite endpoint of death, periprocedural myocardial infarction (MI), ischemic stroke or major bleeding between the two groups during hospitalization. RESULTS: Among 5,545 patients undergoing PCI, 29.8% used the radial approach and 70.2 used the femoral approach. Mean age was 60.8 ± 11.7 years, 68.9% were males and 29% had acute coronary syndromes. There was an increase in the use of the radial approach until 2010 and stabilization in the subsequent year (11.8% in 2008, 26.2% in 2009, 45.1% in 2010 and 42.6% in 2011). Patients using the radial approach had a less complex clinical and angiographic profile. There were no differences in the composite endpoint (5% vs. 5.9%; P = 0.18), death (0.1% vs. 0.8%; P = 0.71), stroke (0.06% vs. 0.03%; P = 0.53) or periprocedural MI (4.5% vs. 3.8%; P = 0.27). However, there was a lower incidence of major bleeding events (0.4% vs. 1.3%; P < 0.01) and vascular complications (0.5% vs. 2.2%; P < 0.01) with the radial approach. CONCLUSIONS: At our interventional cardiology training center, PCI through the radial approach was quickly incorporated and provided, for selected patients, outcomes similar to those of the femoral approach, with decrease of major bleeding and vascular complication rates.