Microcirculation has become a key factor for the study and assessment of tissue perfusion and oxygenation. Detection and assessment of the microvasculature using videomicroscopy from the oral mucosa provides a metric on the density of blood vessels in each single frame. Information pertaining to the density of these microvessels within a field of view can be used to quantitatively monitor and assess the changes occurring in tissue oxygenation and perfusion over time. Automated analysis of this information can be used for real-time diagnostic and therapeutic planning of a number of clinical applications including resuscitation. The objective of this study is to design an automated image processing system to segment microvessels, estimate the density of blood vessels in video recordings, and identify the distribution of blood flow. The proposed algorithm consists of two main stages: video processing and image segmentation. The first step of video processing is stabilization. In the video stabilization step, block matching is applied to the video frames. Similarity is measured by cross-correlation coefficients. The main technique used in the segmentation step is multi-thresholding and pixel verification based on calculated geometric and contrast parameters. Segmentation results and differences of video frames are then used to identify the capillaries with blood flow. After categorizing blood vessels as active or passive, according to the amount of blood flow, quantitative measures identifying microcirculation are calculated. The algorithm is applied to the videos obtained using Microscan Side-stream Dark Field (SDF) imaging technique captured from healthy and critically ill humans/animals. Segmentation results were compared and validated using a blind detailed inspection by experts who used a commercial semi-automated image analysis software program, AVA (Automated Vascular Analysis). The algorithm was found to extract approximately 97% of functionally active capillaries and blood vessels in every frame. The aim of this study is to eliminate the human interaction, increase accuracy and reduce the computation time. The proposed method is an entirely automated process that can perform stabilization, pre-processing, segmentation, and microvessel identification without human intervention. The method may allow for assessment of microcirculatory abnormalities occurring in critically ill and injured patients including close to real-time determination of the adequacy of resuscitation.

Patients with Peripheral Arterial Disease have a reduced capacity for exercise, the exact causes of which are poorly understood. This thesis investigated alternative testing procedures that aim to provide a more complete and precise description of the exercise capacities of these patients. Furthermore, the potential roles of gastrocnemius muscle fibre morphometry, capillary supply and glycogen stores in the exercise tolerance of PAD patients were studied. Study one aimed to determine the effect of test repetition on maximal exercise performance and test-to-test variability in PAD patients using an incremental treadmill walking test (T) (n=5), an incremental cycle test (C) (n=5), and incremental endurance (PF-endurance) and maximal strength (PF-strength) plantar flexion tests (n=5). Tests were conducted once per week for eight weeks. Performance was stable on the T (~530 s) and C (~500 s) tests across the eight weeks. Test-to-test variance on T decreased from 16%CV (CV: coefficient of variation) to 6%CV (p=.21,NS), and from ~8%CV to 2%CV on C (p<.05) over the eight week period. Variance of peak gas exchange variables tended to decrease with performance variance on both tests; however, other physiological variables, and the associated variance levels, were stable throughout the study. PF strength (635-712N) gradually increased over the initial 2-3 weeks (p<.05) which was accompanied by a reduction in variance from ~8%CV to ~3%CV (p<.05). Similarly, PF endurance increased over the first two weeks (~32,000 to 41500 N.s-1) while variance of this measure fell from ~21%CV to ~10%CV (p<.05) over the study duration. It is concluded that the implementation of familiarisation sessions leads to a reduction in whole body and local calf muscular performance variance in patients with PAD. Using a randomised crossover design, study two aimed to compare performance and the physiological and symptomatic responses between a T test and a C test in 16 patients with PAD. Peak exercise time on C (690 s) was greater than that on T (495 s); however the two were significantly correlated (n=16, r=.69, p<.05). Peak HR (120 bpm), VO2 (~1.22 l.min-1) and rate pressure product (~20') did not differ between the two tests, nor did the post exercise ankle pressure (T: 56; C: 61 mmHg). In two subjects with lower back pain during C, the ankle pressure of their "worst" limbs failed to fall by >10mmHg. Performance on both the T and C tests was closely related to the onset of leg symptoms; however the site of pain during C was much more variable than during T. Incremental cycle testing would overcome some of the limitations of treadmill testing (e.g. measurement of mechanical work), and it appears to be an acceptable alternative for measuring the exercise capacity and physiological exercise responses in known claudicants. Use of cycle ergometry for the diagnosis of PAD requires testing in the general population. Study three aimed to compare whole body (T test and C test) and local calf muscular (PF strength and endurance) exercise performance between 16 PAD patients (age: 63 ± 2; BMI: 25.9 ± 1.1) and 13 healthy, sedentary control (CON) subjects (age: 62 ± 1; BMI: 25.9 ± 0.4), and to describe relationships between the whole body and local calf muscular exercise capacities within the two groups. Furthermore, this study aimed to compare several histochemical characteristics of the medial gastrocnemius muscle fibres between PAD and CON, and to establish whether these factors were related to the exercise capacities of both groups. Maximal performance on T was 59% lower in the PAD group compared with the CON group, as was performance on C (50%), PF strength (25%), and PF endurance (58%). Compared with CON, PAD patients had a lower estimated calf muscle mass and a slight reduction (10%) in muscle fibre size (p=.14, NS). They also had a lower proportion of type I fibres (PAD: 49%; CON: 62%) that was offset by a greater proportion of type IIA fibres (PAD: 27%; CON: 16%), and a reduction in the capillary contacts per muscle fibre (PAD: 1.63; CON: 2.12) compared with CON. When expressed relative to fibre area there were no differences in capillarisation between PAD and CON; however this index was significantly related to resting and post exercise ABI in the PAD patients. There were no differences in the mixed muscle [glycogen], nor the optical density of glycogen in the individual fibres, between the two groups. PF endurance was poorly predictive of walking performance, and did not correlate with any of the morphological variables in both groups. Calf muscle mass correlated with PF strength (r=.59 - .62), and strength was correlated with T performance (r= .61 - .63) in both groups. In the PAD patients, T performance was correlated with the cross sectional area (n=12, r=.72, p<.05), capillary contacts (n=10, r=.81, p<.05) and glycogen density (n=9, r=.81, p<.05) of type I fibres. This study confirms that a reduction in calf strength, which appears to be mediated through muscle atrophy, plays some role in the reduced exercise capacity of claudicants. While both fibre area and capillary supply seem to be of relevance to the exercise capacity of PAD patients, these two factors are closely linked and further research is required to establish the determinants, and relative importance of both. An important, and possibly limiting role of carbohydrate oxidisation in PAD patients is supported by the strong relationship between type I glycogen stores and whole body exercise capacity.

Introdução: o uso de drogas vasoativas para restaurar a pressão arterial em pacientes com choque séptico é frequentemente utilizada em medicina intensiva. No entanto, os agentes vasopressores podem acentuar a hipoperfusão esplâncnica durante o choque séptico facilitando a translocação bacteriana e endotoxemia. Neste estudo foram comparados os efeitos de diferentes drogas vasoativas na microcirculação intestinal e nos parâmetros de oxigenação tecidual independentemente de reposição volêmica, num modelo experimental de choque séptico. Métodos: Ratos Wistar Kyoto anestesiados com pentobarbital foram submetidos a choque endotoxêmico através da administração de 2mg/Kg IV de lipopolissacarídeo da Escherichia Coli. A pressão arterial média foi restaurada através da administração de diversas drogas vasoativa, incluindo adrenalina, noradrenalina, fenilefrina, dopamina, dobutamina e uma combinação de noradrenalina com dobutamina. A densidade capilar funcional (DCF) da camada muscular do intestino delgado foi avaliada através de microscopia intravital. Gasometria e concentração de lactato da veia mesentérica superior também foram analisadas. Resultados: A DCF diminui aproximadamente 25% a 60% após a administração intravenosa de adrenalina, noradrenalina e fenilefrina. A administração de dopamina, dobutamina e da associação de noradrenalina com dobutamina não reduziu significativamente a DCF intestinal. A concentração de lactato da veia mesentérica aumentou após a administração de fenilefrina e mostrou uma tendência de aumentar após o uso de adrenalina e noradrenalina enquanto não se observou aumento de lactato após o uso de dopamina, dobutamina e da associação entre noradrenalina e dobutamina. Conclusões: O estudo confirma a presença de uma dissociação entre alterações hemodinâmicas sistêmicas e alterações microcirculatórias num modelo experimental de choque séptico. Os resultados indicam que o uso de dopamina, dobutamina e da associação entre noradrenalina e dobutamina apresentam um efeito de proteção na microcirculação da camada muscular intestinal de ratos submetidos a choque endotoxêmico. / Background: The use of vasoactive drugs to restore arterial blood pressure in patients with septic shock remains a cornerstone of intensive care medicine. However, vasopressors can accentuate the hypoperfusion of the gut during septic shock, allowing bacterial translocation and endotoxemia. In this study, we compared the effects of different vasoactive drugs on intestinal microcirculation and tissue oxygenation, independent of the effects of fluid therapy, in a rat model of endotoxemic shock. Methods: Pentobarbital-anesthetized Wistar Kyoto rats were submitted to endotoxemic shock induced by Escherichia coli lipopolysaccharide (2 mg/kg IV). Arterial blood pressure was normalized by a continuous infusion of different vasoactive drugs, including epinephrine, norepinephrine, phenylephrine, dopamine, dobutamine, or a combination of dobutamine and norepinephrine. The functional capillary density (FCD) of the muscular layer of the small intestine was evaluated by intravital video-microscopy. Mesenteric venous blood gases and lactate concentrations were also analyzed. Results: FCD decreased by approximately 25% to 60% after the IV infusion of epinephrine, norepinephrine, and phenylephrine. Administration of dopamine, dobutamine, and the combination of dobutamine and norepinephrine did not induce significant alterations in gut FCD. In addition, the mesenteric venous lactate concentration increased in the presence of phenylephrine and showed a tendency to increase after the administration of epinephrine and norepinephrine, whereas there was no observable increase after the administration of dopamine, dobutamine, and the combination of dobutamine with norepinephrine. Conclusion: This study confirms dissociation of the systemic hemodynamic and microvascular alterations in an experimental model of septic shock. Moreover, the results indicate that the use of dopamine, dobutamine, and dobutamine in combination with norepinephrine yields a protective effect on the microcirculation of the intestinal muscular layer in endotoxemic rats.

Introdução: o uso de drogas vasoativas para restaurar a pressão arterial em pacientes com choque séptico é frequentemente utilizada em medicina intensiva. No entanto, os agentes vasopressores podem acentuar a hipoperfusão esplâncnica durante o choque séptico facilitando a translocação bacteriana e endotoxemia. Neste estudo foram comparados os efeitos de diferentes drogas vasoativas na microcirculação intestinal e nos parâmetros de oxigenação tecidual independentemente de reposição volêmica, num modelo experimental de choque séptico. Métodos: Ratos Wistar Kyoto anestesiados com pentobarbital foram submetidos a choque endotoxêmico através da administração de 2mg/Kg IV de lipopolissacarídeo da Escherichia Coli. A pressão arterial média foi restaurada através da administração de diversas drogas vasoativa, incluindo adrenalina, noradrenalina, fenilefrina, dopamina, dobutamina e uma combinação de noradrenalina com dobutamina. A densidade capilar funcional (DCF) da camada muscular do intestino delgado foi avaliada através de microscopia intravital. Gasometria e concentração de lactato da veia mesentérica superior também foram analisadas. Resultados: A DCF diminui aproximadamente 25% a 60% após a administração intravenosa de adrenalina, noradrenalina e fenilefrina. A administração de dopamina, dobutamina e da associação de noradrenalina com dobutamina não reduziu significativamente a DCF intestinal. A concentração de lactato da veia mesentérica aumentou após a administração de fenilefrina e mostrou uma tendência de aumentar após o uso de adrenalina e noradrenalina enquanto não se observou aumento de lactato após o uso de dopamina, dobutamina e da associação entre noradrenalina e dobutamina. Conclusões: O estudo confirma a presença de uma dissociação entre alterações hemodinâmicas sistêmicas e alterações microcirculatórias num modelo experimental de choque séptico. Os resultados indicam que o uso de dopamina, dobutamina e da associação entre noradrenalina e dobutamina apresentam um efeito de proteção na microcirculação da camada muscular intestinal de ratos submetidos a choque endotoxêmico. / Background: The use of vasoactive drugs to restore arterial blood pressure in patients with septic shock remains a cornerstone of intensive care medicine. However, vasopressors can accentuate the hypoperfusion of the gut during septic shock, allowing bacterial translocation and endotoxemia. In this study, we compared the effects of different vasoactive drugs on intestinal microcirculation and tissue oxygenation, independent of the effects of fluid therapy, in a rat model of endotoxemic shock. Methods: Pentobarbital-anesthetized Wistar Kyoto rats were submitted to endotoxemic shock induced by Escherichia coli lipopolysaccharide (2 mg/kg IV). Arterial blood pressure was normalized by a continuous infusion of different vasoactive drugs, including epinephrine, norepinephrine, phenylephrine, dopamine, dobutamine, or a combination of dobutamine and norepinephrine. The functional capillary density (FCD) of the muscular layer of the small intestine was evaluated by intravital video-microscopy. Mesenteric venous blood gases and lactate concentrations were also analyzed. Results: FCD decreased by approximately 25% to 60% after the IV infusion of epinephrine, norepinephrine, and phenylephrine. Administration of dopamine, dobutamine, and the combination of dobutamine and norepinephrine did not induce significant alterations in gut FCD. In addition, the mesenteric venous lactate concentration increased in the presence of phenylephrine and showed a tendency to increase after the administration of epinephrine and norepinephrine, whereas there was no observable increase after the administration of dopamine, dobutamine, and the combination of dobutamine with norepinephrine. Conclusion: This study confirms dissociation of the systemic hemodynamic and microvascular alterations in an experimental model of septic shock. Moreover, the results indicate that the use of dopamine, dobutamine, and dobutamine in combination with norepinephrine yields a protective effect on the microcirculation of the intestinal muscular layer in endotoxemic rats.

<p>Skeletal muscle accounts for the largest part of insulin-mediated glucose uptake. Insulin resistance (IR) is the main component of insulin resistance syndrome (IRS) and is an essential cause of a number of cardiovascular risk factors. This thesis investigates the relationships between muscle morphological characteristics and IRS because skeletal muscle is responsible for the majority of glucose uptake.</p><p>In this population-based sample of 70-year-old men, higher proportion of type I fibers as well as higher capillarization were related to higher insulin sensitivity and higher self-reported physical activity, which were related to a lower prevalence of type IIB fibers. Serum triglycerides, HDL cholesterol and plasminogen activator inhibitor-1 (PAI-1) activity were significantly related to fiber distribution and muscle capillarization and muscle morphology, in part, explained the association between these metabolic risk factors with physical activity level. BMI, glucose intolerance, PAI-1 activity, serum FFA concentration, proportion of type IIB fibers, HDL cholesterol level, drug treatment, physical activity level, and W/H ratio together explained 55% of the variation in the insulin sensitivity index. In addition, almost a twofold improvement of the correlations was seen after correcting for intraindividual variation. Glucose tolerant hypertensive subjects showed a lower capillary supply when compared to controls. Capillary density was negatively correlated to the increase in mean arterial pressure over two decades as well as to supine heart rate 20 years before. Interestingly, supine heart rate showed an independent inverse association to the percentage of type I fibers and a positive correlation to the percentage of type IIB muscle fibers. Capillary density and elevated serum free fatty (FFA) acid values were inversely associated with insulin-mediated blood flow and thus to endothelial dysfunction, which has been linked to IR. In fact, capillary density and serum FFA level together explained 71% of the variation in insulin-mediated leg blood flow changes.</p><p>In conclusion, these population-based findings support the observations that muscle morphological features and insulin sensitivity are related to each other. Muscle morphology might explain some of the beneficial impact of physical activity on the components of IRS. Accordingly, we suggest that alterations in muscle morphology should be considered as an essential part of the IRS.</p>

Skeletal muscle accounts for the largest part of insulin-mediated glucose uptake. Insulin resistance (IR) is the main component of insulin resistance syndrome (IRS) and is an essential cause of a number of cardiovascular risk factors. This thesis investigates the relationships between muscle morphological characteristics and IRS because skeletal muscle is responsible for the majority of glucose uptake. In this population-based sample of 70-year-old men, higher proportion of type I fibers as well as higher capillarization were related to higher insulin sensitivity and higher self-reported physical activity, which were related to a lower prevalence of type IIB fibers. Serum triglycerides, HDL cholesterol and plasminogen activator inhibitor-1 (PAI-1) activity were significantly related to fiber distribution and muscle capillarization and muscle morphology, in part, explained the association between these metabolic risk factors with physical activity level. BMI, glucose intolerance, PAI-1 activity, serum FFA concentration, proportion of type IIB fibers, HDL cholesterol level, drug treatment, physical activity level, and W/H ratio together explained 55% of the variation in the insulin sensitivity index. In addition, almost a twofold improvement of the correlations was seen after correcting for intraindividual variation. Glucose tolerant hypertensive subjects showed a lower capillary supply when compared to controls. Capillary density was negatively correlated to the increase in mean arterial pressure over two decades as well as to supine heart rate 20 years before. Interestingly, supine heart rate showed an independent inverse association to the percentage of type I fibers and a positive correlation to the percentage of type IIB muscle fibers. Capillary density and elevated serum free fatty (FFA) acid values were inversely associated with insulin-mediated blood flow and thus to endothelial dysfunction, which has been linked to IR. In fact, capillary density and serum FFA level together explained 71% of the variation in insulin-mediated leg blood flow changes. In conclusion, these population-based findings support the observations that muscle morphological features and insulin sensitivity are related to each other. Muscle morphology might explain some of the beneficial impact of physical activity on the components of IRS. Accordingly, we suggest that alterations in muscle morphology should be considered as an essential part of the IRS.

La survenue d’une défaillance ventriculaire droite est associée à une augmentation de mortalité dans de nombreuses situations cliniques, particulièrement chez les patients atteints d’hypertension pulmonaire chronique. Les mécanismes conduisant à la dysfonction et la défaillance du ventricule droit lorsqu’il est soumis à une surcharge chronique de pression sont complexes et demeurent mal connus. Si une bonne adéquation entre les apports et les besoins accrus en oxygène est essentielle pour le maintien d’une fonction ventriculaire droite adaptée, il semblerait que l’altération de la microvascularisation myocardique pourrait être responsable de la présence d’ischémie myocardique et pourrait contribuer à la transition de la phase adaptée à la phase non adaptée de l’hypertrophie ventriculaire droite. La mitochondrie étant l’organelle oxygéno-dépendante responsable de la production d’énergie, l’intégrité de ses capacités oxydatives est également essentielle au bon fonctionnement du ventricule droit. Il semblerait que le métabolisme mitochondrial soit altéré dans le ventricule droit défaillant mais il existe peu de données au stade précoce dysfonction ventriculaire droite. Afin de mieux comprendre l’importance de ces mécanismes, nous avons modélisé l’hypertension artérielle pulmonaire chez le porc.La première partie de ce travail a consisté à mettre en évidence l’association entre l’altération de la microvascularisation et l’adaptation ventriculaire droite à une surcharge de pression. Pour cela, nous avons modélisé l’hypertension pulmonaire chez deux modèles porcins différents. L’un était un modèle de shunt entre la crosse aortique et le tronc de l’artère pulmonaire (SHUNT), l’autre était un modèle d’hypertension artérielle pulmonaire post-embolique (CTEPH). Un remodelage structurel et fonctionnel du ventricule droit était observé dans les 2 modèles. Dans cette étude, nous avons mis en évidence que la dysfonction ventriculaire droite précoce était associée à (1) un mismatch entre la microvascularisation et l’hypertrophie ventriculaire droite, traduit par une baisse de la densité capillaire, (2) à une baisse du ratio entre la densité capillaire et la charge de travail du ventricule droit (Strokework) et (3) à une augmentation de la fibrose myocardique.Dans la deuxième partie de cette thèse, nous avons étudié et comparé la densité capillaire et la fibrose myocardique ventriculaire droite chez 14 patients atteints de syndrome d’Eisenmenger et 14 patients atteints d’hypertension artérielle pulmonaire chronique. Ces 28 patients présentaient une défaillance ventriculaire droite symptomatique et avaient été traité par une transplantation cœur-poumon. La densité capillaire ventriculaire droite était identique dans les deux groupes et était environ 1,5 fois plus basse que dans un ventricule droit normal, confirmant l’atteinte microvasculaire chez ces patients.La troisième partie de ce travail a consisté à étudier les capacités respiratoires mitochondriales au cours du remodelage ventriculaire droit lorsqu’il est soumis à une surcharge chronique de pression. Il a ainsi été montré que, dans notre modèle porcin d’hypertension artérielle pulmonaire postembolique, les capacités respiratoires mitochondriales mesurées selon la méthode des fibres myocardiques perméabilisées étaient globalement diminuées, précocement dans l’évolution et sans diminution de la masse mitochondriale en microscopie électronique. Nous n’avons pas mis en évidence de modification de d’utilisation préférentiel de substrat par la mitochondrie au cours du temps dans cette étude.De manière générale, ces résultats démontrent le rôle de l’atteinte microvasculaire et de la dysfonction mitochondriale dans la dysfonction ventriculaire droite. Les voies moléculaires communes à ces deux mécanismes (PGC-1, HiF-1 entre autres) font l’objet d’étude afin d’identifier de nouvelles cibles thérapeutiques. / Right ventricular failure is associated with an increased mortality in several clinical features, especially in patients with pulmonary hypertension. Underlying mechanisms of right ventricular dysfunction and failure in chronic pressure overload are complex and still subject to debate. The balance between the supply and the increased need in oxygen is crucial to maintain an adapted right ventricular function. However, an impairment of the myocardial microvascularisation could lead to myocardial ischemia and could participate to the transition between adapted and non-adapted right ventricular hypertrophy. As mitochondrion are involved in the entire oxygen-dependent energy production in cardiomyocytes, their integrity is also essential for a good right ventricular function. It is suggested that mitochondrial metabolism is impaired in right ventricular failure. However, only few data exist at the early stage of right ventricular dysfunction. To better understand the importance of such mechanisms, we used a model of chronic pulmonary hypertension in piglets.The first aim of this thesis was to study the association between microvascularisation impairment and right ventricular adaptation to chronic pressure overload. We compared two different piglet models of pulmonary hypertension. The first model was a systemic-to-pulmonary shunt (SHUNT) between the aortic arch and the pulmonary trunk. The second model reproduced thromboembolic pulmonary hypertension (CTEPH). In this work, we showed that early right ventricular dysfunction was associated with (1) a mismatch between microvascularisation and right ventricular hypertrophy as showed by a decreased capillary density, (2) an importance of the capillary density to right ventricular stroke work ratio and (3) an increased of myocardial fibrosis.In the second part of this thesis, we studied and compared the capillary density and myocardial fibrosis in right ventricles of 14 Eisenmenger Syndrome patients and 14 patients with chronic pulmonary arterial hypertension. All 28 patients had symptomatic right ventricular failure and underwent heart-lung transplantation in our institution. Capillary density was not different between the two groups and was almost 1.5-fold lower than in normal right ventricle, confirming the impairment of microvascularisation in these patients.In the third part of this work, we studied the mitochondrial respiratory capacities in the setting of right ventricular remodeling under chronic pressure overload. Thus, we showed that, in our swine CTEPH model, the mitochondrial respiratory capacities were globally and early impaired. The mitochondrial mass assessed in transmission electronic microscopy was not decreased. We didn’t observe any modification of substrate use over time.Taking together, these results showed that microvascular impairment and mitochondrial dysfunction had an important role in the early right ventricular dysfunction. Molecular pathways involved in both mechanisms are currently studied to find new targeted therapeutics.

Na sepse, o mecanismo desencadeador de morte é a disfunção múltipla de órgãos e sistemas. Com isso a microcirculação é considerada o motor na patogênese da sepse. A perfusão microcirculatória representa um dos principais objetivos para melhorar as taxas de sobrevida. Uma vez reconhecida a síndrome séptica, o protocolo clínico estabelece o uso de fluidoterapia com salina, de forma vigorosa na primeira hora e seguida de suporte inotrópico com Dobutamina. A partir daí foi levantada a hipótese das drogas &#946;-agonistas serem relevantes na recuperação da microcirculação, antes mesmo de seu conhecido papel na recuperação do choque cardiogênico. Assim, estudar o papel da Dobutamina, um &#946;-agonista, na resposta adrenérgica em situação de sepse se faz necessário e urgente e o entendimento de sua ação, associada à reposição volêmica, foi objeto deste estudo. Foram usados no presente estudo, 78 hamsters, induzida a endotoxemia com LPS (2mg/kg/de massa de peso corporal) e divididos em 9 grupos: controle (n=10), endotóxico(n=10), endotóxico tratados com Dobutamina na dose de 5 e 15 &#956;g /kg/min (n=10), Isoproterenol(n=10), ressuscitação volêmica (n=10) e ressuscitação volêmica associada à Dobutamina 5 (n=10) e 15 &#956;g/kg/min (n=4) e Isoproterenol (n=4). Foram comparados os resultados de recuperação da densidade capilar funcional ao longo do tempo entre os grupos, e obteve-se resultado estatisticamente significativo no grupo em que se usa Dobutamina de 5&#956;g/kg/min associada à ressuscitação volêmica p< 0,05. Em conclusão este estudo mostra que o papel da ressuscitação volêmica é crucial na resposta da microcirculação para melhorar a densidade capilar funcional, que a velocidade da hemácia capilar tem relação direta com a melhora na perfusão tecidual e que a associação de recuperação volêmica com solução salina e Dobutamina na dose de 5 &#956;g /kg /min melhora significativamente sua resposta e melhora a perfusão. / During sepsis the mechanism responsible for death is multiple dysfunctions of organs and systems and therefore the microcirculation is considered the motor in the pathogenesis of sepsis and microcirculatory perfusion represents one of the main objectives to improve survival rate. Once one recognizes the septic syndrome, the clinical protocol establishes the use of fluid therapy with physiological saline, in a vigorous way, in the first hour followed by inotropic support with dobutamine. With these facts in mind, our hypothesis is that &#946;-agonist drugs are relevant for microcirculatory recuperation, even before their role was known in the recuperation of cardiogenic shock. In this way, to study the role of dobutamine, a &#946;-agonist, in the adrenergic response in sepsis is needed and urgent. The understanding of its action associated to volume resuscitation was the aim of our study. Seventy-eight male hamsters were used in our study, endotoxemia being induced with LPS (2 mg/kg body weight), divided in 9 groups: control (n=10), endotoxic (n=10), endotoxic treated with dobutamine in the concentrations of 5 and 15 &#956;g/kg/min (n=10, each), isoproterenol (n=10), volume resuscitation associated to dobutamine 5 &#956;g/kg/min (n=10), 15 &#956;g/kg/min (n=4), isoproterenol (n=4) or not (n=10). The microcirculation was observed in the dorsal window chamber and the results compared the recuperation of function capillary density with time and the group treated with dobutamine 5 &#956;g/kg/min associated to volume resuscitation showed a statistically significant improvement (p<0.05) of it. In conclusion, this study has shown that volume resuscitation plays a crucial role in the microcirculatory response in terms of improvement of functional capillary density, the velocity of red blood cells in the capillary has a direct relationship with the improvement of tissue perfusion and the association of volume resuscitation with physiological saline and dobutamine 5 &#956;g/kg/min elicits a significant amelioration of perfusion.

Na sepse, o mecanismo desencadeador de morte é a disfunção múltipla de órgãos e sistemas. Com isso a microcirculação é considerada o motor na patogênese da sepse. A perfusão microcirculatória representa um dos principais objetivos para melhorar as taxas de sobrevida. Uma vez reconhecida a síndrome séptica, o protocolo clínico estabelece o uso de fluidoterapia com salina, de forma vigorosa na primeira hora e seguida de suporte inotrópico com Dobutamina. A partir daí foi levantada a hipótese das drogas &#946;-agonistas serem relevantes na recuperação da microcirculação, antes mesmo de seu conhecido papel na recuperação do choque cardiogênico. Assim, estudar o papel da Dobutamina, um &#946;-agonista, na resposta adrenérgica em situação de sepse se faz necessário e urgente e o entendimento de sua ação, associada à reposição volêmica, foi objeto deste estudo. Foram usados no presente estudo, 78 hamsters, induzida a endotoxemia com LPS (2mg/kg/de massa de peso corporal) e divididos em 9 grupos: controle (n=10), endotóxico(n=10), endotóxico tratados com Dobutamina na dose de 5 e 15 &#956;g /kg/min (n=10), Isoproterenol(n=10), ressuscitação volêmica (n=10) e ressuscitação volêmica associada à Dobutamina 5 (n=10) e 15 &#956;g/kg/min (n=4) e Isoproterenol (n=4). Foram comparados os resultados de recuperação da densidade capilar funcional ao longo do tempo entre os grupos, e obteve-se resultado estatisticamente significativo no grupo em que se usa Dobutamina de 5&#956;g/kg/min associada à ressuscitação volêmica p< 0,05. Em conclusão este estudo mostra que o papel da ressuscitação volêmica é crucial na resposta da microcirculação para melhorar a densidade capilar funcional, que a velocidade da hemácia capilar tem relação direta com a melhora na perfusão tecidual e que a associação de recuperação volêmica com solução salina e Dobutamina na dose de 5 &#956;g /kg /min melhora significativamente sua resposta e melhora a perfusão. / During sepsis the mechanism responsible for death is multiple dysfunctions of organs and systems and therefore the microcirculation is considered the motor in the pathogenesis of sepsis and microcirculatory perfusion represents one of the main objectives to improve survival rate. Once one recognizes the septic syndrome, the clinical protocol establishes the use of fluid therapy with physiological saline, in a vigorous way, in the first hour followed by inotropic support with dobutamine. With these facts in mind, our hypothesis is that &#946;-agonist drugs are relevant for microcirculatory recuperation, even before their role was known in the recuperation of cardiogenic shock. In this way, to study the role of dobutamine, a &#946;-agonist, in the adrenergic response in sepsis is needed and urgent. The understanding of its action associated to volume resuscitation was the aim of our study. Seventy-eight male hamsters were used in our study, endotoxemia being induced with LPS (2 mg/kg body weight), divided in 9 groups: control (n=10), endotoxic (n=10), endotoxic treated with dobutamine in the concentrations of 5 and 15 &#956;g/kg/min (n=10, each), isoproterenol (n=10), volume resuscitation associated to dobutamine 5 &#956;g/kg/min (n=10), 15 &#956;g/kg/min (n=4), isoproterenol (n=4) or not (n=10). The microcirculation was observed in the dorsal window chamber and the results compared the recuperation of function capillary density with time and the group treated with dobutamine 5 &#956;g/kg/min associated to volume resuscitation showed a statistically significant improvement (p<0.05) of it. In conclusion, this study has shown that volume resuscitation plays a crucial role in the microcirculatory response in terms of improvement of functional capillary density, the velocity of red blood cells in the capillary has a direct relationship with the improvement of tissue perfusion and the association of volume resuscitation with physiological saline and dobutamine 5 &#956;g/kg/min elicits a significant amelioration of perfusion.

Advancements in clinical care have led to a growing cohort of preterm-born individuals now entering adulthood. Before birth, such adults were often exposed to a suboptimal intrauterine environment, and after delivery, key developmental stages that would normally occur in utero during the third trimester had to take place under ex utero physiological conditions. Through detailed cardiovascular phenotyping, this thesis investigates the cardiovascular changes in preterm-born young adults, utilising a cohort of individuals with data collection since recruitment at birth. The detailed perinatal information was first used to design nested case-control studies to investigate the effects of early lipid and glucocorticoid exposure on long-term cardiovascular physiology in individuals born preterm. It was demonstrated that intravenous lipid administration leads to an artificial elevation of total cholesterol levels in immediate postnatal life, which is associated with long-term changes in aortic and left ventricular function proportional to the degree of cholesterol elevation. Additionally, exposure to antenatal glucocorticoids relates to a regional increase in aortic arch stiffness in young adulthood, as well as changes in glucose metabolism. It was then shown that young adults born preterm have increased left ventricular mass, out of proportion to blood pressure, and a unique three-dimensional left ventricular geometry, with reduced systolic and diastolic function compared to term-born controls. Similarly, they also show distinct differences in the right ventricle, with increased right ventricular mass and a proportion having clinically impaired right ventricular systolic function. Finally, it was demonstrated that preterm-born individuals have increased circulating levels of antiangiogenic factors in young adulthood, which relate to capillary rarefaction and blood pressure elevation. These findings are of considerable public health relevance given that nearly 10% of births are now preterm. Understanding whether modification of these variations in cardiovascular structure and function prevent the development of cardiovascular disease in this growing subgroup of the population will be of future interest.