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Graduation date: 2006

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-08-05T13:04:39Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese_Final_versão_biblioteca (2).pdf: 8187833 bytes, checksum: e76d125aa3b04c57265a2a3a15aca042 (MD5) / Made available in DSpace on 2016-08-05T13:04:39Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese_Final_versão_biblioteca (2).pdf: 8187833 bytes, checksum: e76d125aa3b04c57265a2a3a15aca042 (MD5) Previous issue date: 2016-02-24 / Introdução: Os tecidos adiposos subcutâneo (TAS) e, sobretudo, o visceral (TAV), quando em excesso, predizem riscos cardiometabólicos. Os métodos de quantificação do TAV e do TAS têm uso limitado na prática clínica sendo necessário identificar um marcador de alta validade para estimar a adiposidade visceral, que seja simples e de baixo custo. A circunferência abdominal (CA) é uma medida comumente empregada como proxy do TAV. No entanto, existe uma grande variação de protocolos para sua obtenção, comprometendo seu uso e comparação de resultados. Objetivos: Estimar a concentração de TAV e TAS e os fatores associados; estimar o grau de variabilidade da CA em diferentes sítios anatômicos e comparar a performance dos locais de medição como preditores de TAV, TAS e anormalidades cardiometabólicas; desenvolver um modelo preditivo para estimar o volume de TAV, a partir de idade e parâmetros antropométricos factíveis de serem utilizados na prática clínica; avaliar o efeito da perda de peso no TAV e TAS, e os efeitos da redução do TAV no perfil cardiometabólico. Métodos: Foram desenvolvidos dois delineamentos: um corte transversal para avaliar os fatores associados à concentração de TAV e TAS e aspectos metodológicos na estimativa do TAV; e uma intervenção clínica para verificar o efeito da restrição calórica no TAV, após um período de 3 meses, envolvendo adultos com excesso de peso, atendidos em hospital no Nordeste brasileiro. O TAV e TAS foram quantificados por tomografia computadorizada. A CA foi avaliada em seis sítios de medição. Outros parâmetros antropométricos avaliados foram: Índice de Massa Corpórea (IMC), Razão Cintura Quadril, Razão Cintura-Estatura, Diâmetro Sagital, Índice Sagital, Índice de Conicidade, Circunferência do Pescoço, Razão Pescoço-Coxa, Razão Cintura-Coxa e Índice de Adiposidade Corporal. Resultados: O estudo transversal envolveu 109 pacientes (50,3±12,2anos). Os homens apresentaram maior concentração de TAV. Presença de hipertensão arterial (HA), maior IMC e menor consumo de alimentos protetores associaram-se à maior concentração de TAV em homens (R²ajustado=46,4%); maior idade, presença de HA, maior IMC e consumo de álcool foram associadas ao TAV em mulheres (R2ajustado=17,6%). Houve maior variabilidade nos valores de CA no sexo feminino. A cintura mínima apresentou maior correlação com o TAV (r=0,70) em homens. Entre as mulheres, as medidas da CA apresentaram maior correlação com o TAS. A equação preditiva para os homens apresentou maior poder preditivo (64,1%), que o modelo desenvolvido para as mulheres (40,4%). Dos 51 pacientes submetidos à intervenção dietética, houve uma redução ponderal de 5,8(±6,2)% nos homens, com redução de 11,2(±7,9)% de TAV; 6,8(±11,2)% de TAS e 54,9% nos triglicérides. Entre as mulheres, a redução de 4,1(±2,5)% do peso inicial, resultou em uma diminuição de 11,1(±8,8)% de TAV; 5,6(±7,4)% de TAS, 12,2% no colesterol e 31,4% nos triglicérides. Conclusão: Múltiplos fatores determinam o volume de TAV e TAS em homens e mulheres. Maior variabilidade entre os sítios de medição de CA foi observada no sexo feminino. Nos homens, a cintura mínima apresentou melhor poder preditivo do TAV. Uma perda ponderal de aproximadamente 5% promoveu uma mobilização substancial de TAV e TAS, com potenciais benefícios cardiometabólicos. / Introduction: When in excess, subcutaneous adipose tissue (SAT), and, remarkably, visceral adipose tissue (VAT) predict cardiometabolic risks. Quantification methods of SAT, and VAT have limited use in clinical practice, and the identification of a simple, low cost, high value marker, to estimate visceral fat, is nedeed. Abdominal cirumference (AC) is a common method used as VAT‟s proxy. However, there‟s a great protocol variation for its execution, wich jeorpadizes its use, and the results‟ comparison. Objectives: To estimate concentration of VAT and SAT , and associated factors; to estimate variability of AC in different anatomical regions, and compare measurament sites performance as predictors of SAT, VAT, and cardiometabolic anormalities; to develop a predective model to estimate volume of VAT from athropometric criteria easily applied in clinical practice; to evaluate weight loss effect on VAT, and SAT, and also VAT reduction effects on cardiometabolic profile. Method: Two designs were developed: a cross-sectional study to analyse associated factors to SAT and VAT concentration, and methodological aspects of VAT valuation; a clinical intervention to verify the result of calorie restriction on VAT after 3 months, involving overweight adults assisted in a northeastern Brazilian hospital. VAT and SAT were quantified by computerized tomography. AC was measured in six different sites. Other anthropometric parameters evaluated were: Body Mass Index (BMI), Waist-Hip Ratio, Waist-Height Ratio, Sagittal Diameter, Sagittal Index, Conicity Index, Neck Circumference, Neck-Thigh Ratio, Waist-Thigh Ratio, Body Adiposity Index. Results: The transversal study involved 109 patients (50,3±12,2years). Higher concentration of VAT was found in males. Arterial Hypertension (AH), higher BMI , and lower ingestion of protective food were associated with higher concentration of VAT in men (R²adjusted=46.4%); older age, AH, higher BMI e alcohol consumption were associated to VAT in women (R2adjusted=17.6%). Greater variability on AC values was found in females. Minimal waist size showed greater correlation with VAT (r=0,70) in males. Among women, AC measures demonstrated greater correlation with SAT. Predictive equation for men exposed higher predictive power (64.1%) than the model developed for women (40.4%). There was a weight loss of 5.8(±6.2)% in males from the 51 patientes submitted to intervention on diet, a reduction of VAT of 11.2(±7.9)%; 6.8(±11.2)% of SAT, and 54.9% of triglycerides. Among females, reduction of 4.1(±2.5)% from the initial weight resulted in a decrease of 11.1(±8.8)% of VAT; 5.6(±7.4)% of SAT, 12.2% of choleterol, and 31,4% of triglycerides. Conclusion: Multiple factors determine volume of VAT and SAT in men and women. Greater variability of measurement sites were observed in females. Among men, minimal waist determined better predictive power of VAT. A 5% loss of weight promoted a significant mobilization of SAT and VAT, with potential cardiometabolic benefits.

Le principal objectif de cette thèse est de caractériser l'écoulement dans un anévrisme abdominal aortique (AAA) sous différentes conditions physiologiques et à différents stades de son développement. Cette étude est consacrée aux AAA axisymétriques, modélisés comme une dilatation de profil gaussien et de section circulaire. Ainsi, les résultats s'appliquent surtout aux étapes précoces du développement d'un AAA. Le modèle d'AAA est caractérisé par une hauteur maximale H et une largeur W, l'unité de mesure étant le diamètre d'entrée de l'artère. Pour commencer, la dynamique est étudiée pour les écoulements stationnaires. La stabilité globale de ces écoulements de base est analysée en calculant les valeurs propres et les fonctions propres pour des perturbations de faible amplitude. Pour comprendre les mécanismes d'instabilité, le transfer d'énergie entre l'écoulement de base et les perturbations est calculé. L'écoulement pour des AAA peu profonds (ou de grande longueur) se déstabilise par un mécanisme de ‘lift-up' et les perturbations amplifiées sont stationnaires. Des anévrismes plus localisés (ou plus profonds) deviennent instables pour des nombres de Reynolds plus élevés, sans doute par instabilité elliptique ; dans cette situation, les perturbations sont des modes oscillants. Dans le cas des écoulements pulsés, deux types de profil de débit physiologique ont été considérés dans cette étude, correspondant à une situation de repos ou d'exercice physique. Ces écoulements restent collés aux parois pendant la phase de systole et un écoulement décollé est généralement observé pendant la décélération après le maximum de systole. Dans cette phase, un vortex se forme à l'extrémité aval. Ce vortex s'agrandit au cours du temps et impacte l'extrémité aval de l'AAA, ce qui conduit à de forts gradients de contrainte pariétale, qui ne sont pas observés dans les cas sains. Il a été observé que les conditions d'écoulement varient significativement avec les nombre de Womersley (Wo) et de Reynolds (Re); l'écoulement reste attaché aux parois plus longtemps pour des nombres de Womersley croissants. Le principal effet d'une augmentation de Re est un renforcement du vortex primaire qui se forme après le maximum de systole. Les décollements de l'écoulement, l'impact de vortex au bord aval de l'AAA ou encore de faibles contraintes pariétales oscillantes (des caractéristiques importantes dans les cas d'anévrismes pathologiques) sont observés même pour des anévrismes de faible profondeur. Pour des anévrismes plus développés, des vortex multiples sont observés tout au long du cycle dans la cavité de l'AAA. Une analyse de stabilité de ces écoulements de base pulsés a montré que le maximum des perturbations se développe vers l'extérmité aval des AAA. Cependant, les perturbations ne sont pas complètement confinées dans la cavité de l'AAA et se développent aussi au-delà en aval. On en déduit qu'une fois qu'un AAA s'est développé, les perturbations affectent aussi les artères saines en aval de l'AAA. Enfin, en considérant deux profils équivalents d'AAA, de formes sinusoïdale et gaussienne, la sensibilité des résultats aux détails de la géométrie a pu être établie / The main objective of this thesis is to characterise the flow fields observed in an abdominal aortic aneurysm (AAA) under different physiological conditions during its progressive enlargement. An axisymmetric AAA, modeled as an inflation of Gaussian shape on a vessel of circular cross-section, is considered in the present study. This means that the results are more significant for the early stages of growth of an AAA. The model AAA is characterized by a maximum height H and width W, made dimensionless by the upstream vessel diameter. To begin with, the flow characteristics in AAAs are investigated using steady flows. The global linear stability of the base flows is analysed by determining the eigenfrequencies and eigenfunctions of small-amplitude perturbations. In order to understand the instability mechanisms, the energy transfer between the base flow and the perturbations is computed. The flow in relatively shallow aneurysms (of relatively large width) become unstable by the lift-up mechanism and have a perturbation flow which is characterized by stationary, growing modes. More localized aneurysms (with relatively small width) become unstable at larger Reynolds numbers, presumably by an elliptic instability mechanism; in this case the perturbation flow is characterized by oscillatory modes. For the case of pulsatile flows, two types of physiological flowrate waveforms are considered in our study, corresponding to rest and exercise conditions. The flows are observed to remain attached to the walls during the systolic phase, with flow separation generally observed during the deceleration after the peak systole. During this phase, the vorticity is found to roll-up into a vortex at the proximal end. This vortex enlarges with time and impinges at the downstream end of the AAA, resulting in large spatial gradients of wall shear stress (WSS) along the wall, which are not found in the healthy case. The flow conditions are observed to vary significantly with Womersley (Wo) and Reynolds (Re) numbers, with the flow remaining attached to the walls for longer times, as the Womersley number Wo increases. The principal effect of increasing Re is that the primary vortex formed after peak systole is stronger. Clinically relevant flow characteristics of aneurysmal flow, i.e. detachement of flow and impingement on the distal end, the presence of low oscillatory WSS within the AAA, are observed even for very shallow aneurysms. For deep aneurysms, multiple vortices are observed throughout the cycle within the AAA cavity. Stability analysis of pulsatile base flows reveals that the maximum values of the perturbations are observed near the distal end of the AAA. However, they are not entirely confined to the AAA cavity and extend downstream, implying that once an AAA is formed, the disturbed flow conditions spread even to the undeformed arterial walls downstream of the AAA. Finally, by considering two equivalent AAA shapes modeled by a sinusoidal and a gaussian function, the sensitivity

Thesis (doctoral)--Lund University, 1998. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1998. / Added t.p. with thesis statement inserted.

Previous studies demonstrated that increased levels of C-reactive protein (CRP) after colo-rectal surgery are correlated to postoperative organ-space surgical site infection (OS-SSI) even at 48 hours time point. Such early inflammatory response might suggest that intraoperative haemodynamic factors might influence intestinal anastomosis healing. Objective: To evaluate the correlation between early postoperative venous lactate, CRP at 48 hours and intraoperative haemodynamics and the incidence of OS-SSI in patients operated on elective colorectal surgery with anastomosis. Materials and methods. From March 2013 to August 2014, all patients undergoing colorectal surgery with anastomosis were prospectively included. Levels of venous lactate were measured at the end of surgery (L-PO) and at 6 (L-6) and 24 hours afterwards (L-24). CRP levels at postoperative 48 hours (CRP-48) were also measured. We compared lactate levels and CRP values in patients with and without OS-SSI infection. Proportion of time that patients developed intraoperative systolic hypotension (SBP<100 mmHg) or tachycardia (>90 bpm) were also assessed. Data are summarized as mean ± SD. To analyze data, Student t-test and a logistic regression model with L-0 and CRP-48 with a ROC curve of this model were performed. Results. One hundred patients were included, with an age of 69±11 years-old. Forty-four percent of patients were operated by laparoscopic approach. Eleven out of 100 patients (11%) complained OS-SSI. OS-SSI patients had significantly higher venous lactate levels at L-PO and at L-24 (3,2 vs 1,5, p<0,001 and 1,8 vs 1,2, p=0,0002, mmol/L, respectively). Overall, patients with L-PO >2,5 mmol/L had higher CRP-48 levels (140±85 vs. 78±57 mg/L, respectively, p=0,001). With the logistic regression model with L-PO and CRP-48 and ROC curve of this model: in patients with more than 0,26 of probability, OS-SSI should be discarded (AUC 0,899). Analysing haemodynamics behaviour, patients who developed OS-SSI remained hypotensive (50 % vs 30%, p=0,03) and tachycardic (18% vs 5%, p=0,02) for a longer period of time. Conclusions. Early postoperative venous lactate and CRP at 48 hours correlated to OS-SSI appearance. Determination of biological markers and haemodynamics goal-oriented intraoperative management might improve the postoperative outcome.

No description available.

AAA disease remains a common and life threatening condition, predominantly affecting men of retirement age. Whilst clinical studies have done much to predict the course of this disease, understanding the pathogenesis has been complicated by both a multi-factorial aetiology as well as several poorly defined stages to the disease (formation, growth and rupture). Evidence points to a considerable inheritable component to this condition, but as yet, associations with identified genetic variants are few and weak. This thesis describes the current understanding of the molecular mechanisms behind AAA pathogenesis, concentrating on aneurysm formation and growth. A meta-analysis of published candidate gene studies identified three genes with small but significant effects on risk of developing AAA (ACE, MTHFR and MMP9) and none with a significant effect on AAA growth. Further examination of five genes connected the Renin-Angiotensin System, using three distinct case control series, demonstrated the strongest reported association to date with AAA disease risk, with AGTR1+1166A>C. (OR 1.55 [1.30-1.83, p=5x10-7]). An interest in the role of the TGF-β pathway in AAA formation and growth has developed from the recent illumination of the mechanism behind aneurysm aetiology in Marfan syndrome. Haplotype analysis was used to investigate five genes coding for TGF-β and its binding protein (LTBP). Variants in TGFB3 and LTBP4 were significantly associated with altered AAA growth. The importance of inflammatory process was also supported by observations made in a very large longitudinal data set of AAA growth. Anti-inflammatory drugs, together with anti-platelet drugs and drugs used in diabetes, were significantly associated with decreased AAA growth independent of confounding factors. In conclusion, this thesis demonstrates; a role for the RAS in AAA formation; TGF-β in AAA growth; and anti-inflammatory drugs as potentially disease modifying. In addition, observations have also been made concerning a two tier effect illuding to the nature AAA progression.