Cements of doped calcium phosphates for bone implantation

Doutoramento em Ciência e Engenharia de MateriaisO principal objectivo deste estudo foi o desenvolvimento de cimentos à base de fosfatos de cálcio dopados com Mg, Sr e Zn, para aplicações clínicas. A síntese dos pós foi obtida através de reacções de precipitação, seguido de tratamento térmico de forma a obter as fases mais apropriadas, a (alpha) e b (beta)-TCP. A caracterização dos pós envolveu a quantificação de fases e o refinamento estrutural de fases através da análise de difracção de raios-X por refinamento de Rietveld, bem como, análise da área superficial por BET, e respectivos tamanhos de partícula. Os cimentos foram preparados através da mistura dos pós com meios líquidos diferentes, usando ácido cítrico como acelerador de presa, e o polietilenoglicol (PEG) e o hidroxil propilmetilcelulose (HMPC) como agentes gelificantes. A formação da brushite foi um dos produtos resultantes obtidos da hidratação dos cimentos. Do ponto de vista de aplicação clínica, os cimentos foram caracterizados em termos de presa, injectabilidade, análise calorimétrica e resistência mecânica. Os presentes resultados demonstraram que a incorporação de iões nos cimentos levou a uma melhoria significativa das propriedades destes quando comparados com TCP puro. Os resultados obtidos demonstraram ainda que o tempo inicial de presa tende a decrescer na presença de modificadores reológicos, uma vez que estes aumentam a viscosidade das pastas, e aumenta com o acréscimo da razão L/P, tendo sido considerada a gama de 0.30-0.34 mL g-1 como aceitável para manusear as pastas. As pastas cimentícias apresentaram uma boa injectabilidade, nomeadamente o seu comportamento após extrusão, com aplicação de uma força máxima de 100 N. Investigou-se ainda, com estes testes, a ausência do efeito de “filter-pressing” e que as pastas foram totalmente expelidas para uma razão L/P de 0.36 mLg-1. Os testes de calorimetria isotérmica demonstraram que as pastas apresentam reacções exotérmicas, referentes à dissolução dos pós de partida e à formação de fases intermédias; e à nucleação e crescimento da brushite. Resistências à compressão dos cimentos estudados, após imersão numa solução de PBS durante 48h situam-se entre 1-30 MPa, valores reportados para o osso trabecular. Testes de citotoxicidade, bioactividade e biocompatibilidade dos cimentos foram obtidos através de testes de culturas celulares, mostrando a nãotoxicidade destes. A biocompatibilidade in vivo e a reabsorção dos cimentos foram avaliadas em estudos histológicos e histomorfométricos de secções descalcificadas obtidas através de ensaios de experimentação animal, usando o porco como modelo. Os resultados mostraram que os cimentos implantados são biocompatíveis e osteocondutivos, sem evidência de reacções infecciosas, e portanto, bons candidatos para aplicação como substitutos ósseos.The main objective of this study was the development of cements based on calcium phosphates doped with Mg, Sr and Zn, for clinical applications. Powder synthesis was obtained through precipitation reactions, followed by heat treatment in order to obtain appropriate phases, a (alpha) and b (beta)-TCP. The cements were prepared through mixing the powders with different liquids, using citric acid as setting accelerator, and polyethyleneglycol and hydroxyl propylmethylcellulose as gelling agents. Brushite was the end product of the hydration reaction. Injectability and setting behaviour were accessed through rheological measurements, extrusion, calorimetric analysis, Vicat and Gilmore needles. Phase quantification and the structural refinement of powders and cements were determined through X-ray diffraction with Rietveld refinement, as well as, BET specific surface area and particle size analysis. Mechanical strengths of wet hardened cements were evaluated. The results obtained showed that the incorporation of ions into cements led to a significant improvement of their overall properties. Initial setting time increased in the presence of rheological modifiers due to their specific roles at the solid/liquid interface and with increasing L/P ratio. Acceptable workability pastes were obtained for L/P ratios in the range of 0.30-0.34 mL g-1. The cement pastes presented good injectability even under a maximum applied force of 100 N. Filter pressing effects were absent, and all cement pastes could be fully injected for LPR > 0.36 mL g-1. Isothermal calorimetry revealed that hydration reactions produce exothermic effects due to: (i) dissolution of the starting powders and formation of intermediate phases; and (ii) nucleation and growth of brushite crystals. The intensity of the exothermic effects depended on doping element, being stronger in the case of Sr. Wet compressive strength of the cement specimens (after immersion in PBS solution for 48 h) was in the range of values reported for trabecular bone (10-30 MPa). Cell cultures used to evaluate citotoxicity, bioactivity and biocompatibility of cements revealed no toxic effects. The biocompatibility in vivo and cements resorption were evaluated using a pig model through histological and histomorphometric studies of decalcified sections. The results show that the implanted cements are biocompatible and osteoconductive, without foreign body reaction. These properties make them good candidates for applications as bone substitutes

Preparação de vidros e vitro-cerâmicos do sistema SiO2-AL2O3-B2O3-CaO-MgO-Li2O-(K, NA)2O-F para potenciais aplicações em medicina dentária

Mestrado em Engenharia de MateriaisO presente trabalho teve por finalidade investigar a influência da substituição catiónica em vidros e vitro-cerâmicos à base de Ca-mica e a produção de materiais com propriedades adequadas para aplicações de interesse tecnológico. Considerou-se como referência a composição CaMg3Al2Si2O10F2 e investigou-se a influência da substituição (parcial ou completa) de Mg por Li e de Al por B no processo de cristalização e nas propriedades dos vitro-cerâmicos resultantes. Os materiais produzidos foram caracterizados por recurso a diversas técnicas experimentais, nomeadamente, análises térmicas (ATD e dilatometria), difracção de raios X, espectroscopia de Raman, microscopia electrónica de varrimento e espectroscopia de energia dispersiva. A densidade e as propriedades mecânicas foram avaliadas pelo de método de Arquimedes, microdureza de Vickers e ensaios mecânicos à flexão, respectivamente, enquanto para o estudo da durabilidade química se recorreu à imersão em ácido acético. Os resultados experimentais mostraram que o vidro de referência só funde adequadamente a cerca de 1550ºC, enquanto todos os vidros dele derivados puderam ser facilmente fundidos e vazados a temperaturas baixas (≈1350ºC). A cristalização e propriedades dos vitro-cerâmicos obtidos a partir dos vidros base mostraram-se muito sensíveis à substituição dos catiões. O início da cristalização foi deslocado para temperaturas mais baixas na presença de B e de Li. Por outro lado, a substituição completa de Al por B causou um decréscimo da cristalinidade dos vitro-cerâmicos, uma fusão parcial após tratamento térmico a temperaturas acima de 850ºC, e tornou os vidros mais propensos a uma cristalização em volume. Os vidros apresentaram unidades Q1, Q2, e Q3 do silício e ligações Al∅4 - na presença de Al, e/ou unidades triangulares B∅2O- e tetraédricas B∅4 - na presença de B. A presença de Li não causou alterações significativas a nível estrutural, enquanto que a presença de fósforo favoreceu a formação de unidades isoladas de coordenação tetraédrica do tipo PO4 4-. A composição de referência foi a única em que se formou a mica (xantofilite) após tratamento térmico a 650ºC. A substituição, parcial ou completa, de Mg por Li e de Al por B levou à formação de variadas fases, tais como, inossilicatos (piroxenas e anfíbolas), nesossilicatos (humite e forsterite) e, num caso, feldspato de Ca (anortite). Os vitrocerâmicos com P na sua composição apresentaram fases variadas, tais como, diopsido, borato de Mg, fosfito de B, SiO2e CaF2. O uso de uma rocha natural à base de Li incorporou inevitavelmente outros metais alcalinos, como K e Na. O vidro contendo todos os catiões (Li, Na, K, Al) mostrou-se mais propenso a uma cristalização homogénea em volume. Os vitro-cerâmicos apresentaram diversas fases cristalinas a diferentes temperaturas (anfíbolas, Ca-mica, forsterite, espinela e KLi-mica. Estes materiais são mais baratos e apresentaram boas propriedades ópticas de brancura, translucidezopacidade, e propriedades químicas e mecânicas promissoras para diversas aplicações. ABSTRACT: The present work aimed at investigating the influence of cation substitution in glass and glass-ceramics based on Ca-mica and at the production of materials with suitable properties for applications of technological interest. Considering the composition CaMg3Al2Si2O10F2 as reference, the influence of substitution (partial or complete) of Li for Mg and B for Al on crystallization process and on the properties of the resulting glassceramics, was investigated. Several experimental techniques were employed for the characterization of the produced materials, such as thermal analysis (DTA and dilatometry), X-ray diffraction, Raman spectroscopy, scanning electron microscopy and energy dispersive spectroscopy. The density and the mechanical properties were measured by the Archimedes method, and Vickers microhardness and flexural strength measurement, respectively, while the study of chemical durability was made by imersion in acetic acid. The experimental results showed that the reference glass was melted at near 1550ºC, while all the other glasses derivated from it were easily melted and cast at lower temperatures (≈1350ºC). The crystallization and the properties of glass-ceramics crystallized from the base glasses were very sensitive on cations substitutions. Initial the onset of crystallization was shifted to lower temperatures in the presence of B and Li. On the other hand, the complete substitution of B for Al caused significant lowering of crystallinity in the glass-ceramics, partial melting after heat treatment at temperatures higher than 850ºC, and the resulting glasses became prone to bulk crystallization. The glasses showed Q1, Q2, eQ3 silicon units and Al∅4 -, in the presence of Al, and/or triangular, B∅2O-, and tetrahedral units B∅4 - in the presence of B. The presence of Li didn’t cause significative modifications in the structure, while the presence of P favoured the formation of isolated tetrahedral coordinated units of type PO4 4-. The formation of mica (xanthophyllite) only occurred in the case of reference composition after heat treatment at 650ºC. Substitution, partial or complete, of Li for Mg and B for Al showed the formation of a variety of phases such as, inosilicates (pyroxenes and amphiboles), nesosilicates (humite and forsterite) and, in a particular case, Cafeldspar (anortite). The glass-ceramics with P in their composition showed different phases, such as, diopside, Mg-borate, B-phosphite, silica and CaF2. The use of a natural rock based on Li inevitably introduced other alkalis metals, such as K and Na. The glasses which contain all the cations (Li, Na, K, Al) were prone to homogenous bulk crystallization. The glassceramics showed different crystalline phases at different temperatures (amphiboles, Ca-mica, forsterite, spinel and KLi-mica). These materials are cheaper and exhibited good optical properties of whiteness, translucency-opalescence, and chemical and mechanical properties which are promising for several applications

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

NEOTROPICAL ALIEN MAMMALS: a data set of occurrence and abundance of alien mammals in the Neotropics

Biological invasion is one of the main threats to native biodiversity. For a species to become invasive, it must be voluntarily or involuntarily introduced by humans into a nonnative habitat. Mammals were among first taxa to be introduced worldwide for game, meat, and labor, yet the number of species introduced in the Neotropics remains unknown. In this data set, we make available occurrence and abundance data on mammal species that (1) transposed a geographical barrier and (2) were voluntarily or involuntarily introduced by humans into the Neotropics. Our data set is composed of 73,738 historical and current georeferenced records on alien mammal species of which around 96% correspond to occurrence data on 77 species belonging to eight orders and 26 families. Data cover 26 continental countries in the Neotropics, ranging from Mexico and its frontier regions (southern Florida and coastal-central Florida in the southeast United States) to Argentina, Paraguay, Chile, and Uruguay, and the 13 countries of Caribbean islands. Our data set also includes neotropical species (e.g., Callithrix sp., Myocastor coypus, Nasua nasua) considered alien in particular areas of Neotropics. The most numerous species in terms of records are from Bos sp. (n = 37,782), Sus scrofa (n = 6,730), and Canis familiaris (n = 10,084); 17 species were represented by only one record (e.g., Syncerus caffer, Cervus timorensis, Cervus unicolor, Canis latrans). Primates have the highest number of species in the data set (n = 20 species), partly because of uncertainties regarding taxonomic identification of the genera Callithrix, which includes the species Callithrix aurita, Callithrix flaviceps, Callithrix geoffroyi, Callithrix jacchus, Callithrix kuhlii, Callithrix penicillata, and their hybrids. This unique data set will be a valuable source of information on invasion risk assessments, biodiversity redistribution and conservation-related research. There are no copyright restrictions. Please cite this data paper when using the data in publications. We also request that researchers and teachers inform us on how they are using the data

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Health-status outcomes with invasive or conservative care in coronary disease

BACKGROUND In the ISCHEMIA trial, an invasive strategy with angiographic assessment and revascularization did not reduce clinical events among patients with stable ischemic heart disease and moderate or severe ischemia. A secondary objective of the trial was to assess angina-related health status among these patients. METHODS We assessed angina-related symptoms, function, and quality of life with the Seattle Angina Questionnaire (SAQ) at randomization, at months 1.5, 3, and 6, and every 6 months thereafter in participants who had been randomly assigned to an invasive treatment strategy (2295 participants) or a conservative strategy (2322). Mixed-effects cumulative probability models within a Bayesian framework were used to estimate differences between the treatment groups. The primary outcome of this health-status analysis was the SAQ summary score (scores range from 0 to 100, with higher scores indicating better health status). All analyses were performed in the overall population and according to baseline angina frequency. RESULTS At baseline, 35% of patients reported having no angina in the previous month. SAQ summary scores increased in both treatment groups, with increases at 3, 12, and 36 months that were 4.1 points (95% credible interval, 3.2 to 5.0), 4.2 points (95% credible interval, 3.3 to 5.1), and 2.9 points (95% credible interval, 2.2 to 3.7) higher with the invasive strategy than with the conservative strategy. Differences were larger among participants who had more frequent angina at baseline (8.5 vs. 0.1 points at 3 months and 5.3 vs. 1.2 points at 36 months among participants with daily or weekly angina as compared with no angina). CONCLUSIONS In the overall trial population with moderate or severe ischemia, which included 35% of participants without angina at baseline, patients randomly assigned to the invasive strategy had greater improvement in angina-related health status than those assigned to the conservative strategy. The modest mean differences favoring the invasive strategy in the overall group reflected minimal differences among asymptomatic patients and larger differences among patients who had had angina at baseline