RESUMO
OBJECTIVES: To investigate the association between priapism in men with sickle cell anemia (SCA) and hemorheological and hemolytical parameters. MATERIALS AND METHODS: Fifty-eight men with SCA (median age: 38 years) were included; 28 who had experienced priapism at least once during their life (priapism group) and 30 who never experienced this complication (control group). Twenty-two patients were treated with hydroxycarbamide, 11 in each group. All patients were at steady state at the time of inclusion. Hematological and biochemical parameters were obtained through routine procedures. The Laser-assisted Optical Rotational Cell Analyzer was used to measure red blood cell (RBC) deformability at 30 Pa (ektacytometry) and RBC aggregation properties (laser backscatter versus time). Blood viscosity was measured at a shear rate of 225 s-1 using a cone/plate viscometer. A principal component analysis was performed on 4 hemolytic markers (i.e., lactate dehydrogenase (LDH), aspartate aminotransferase (ASAT), total bilirubin (BIL) levels and reticulocyte (RET) percentage) to calculate a hemolytic index. RESULTS: Compared to the control group, patients with priapism exhibited higher ASAT (p = 0.01), LDH (p = 0.03), RET (p = 0.03) levels and hemolytic indices (p = 0.02). Higher RBC aggregates strength (p = 0.01) and lower RBC deformability (p = 0.005) were observed in patients with priapism compared to controls. After removing the hydroxycarbamide-treated patients, RBC deformability (p = 0.01) and RBC aggregate strength (p = 0.03) were still different between the two groups, and patients with priapism exhibited significantly higher hemolytic indices (p = 0.01) than controls. CONCLUSION: Our results confirm that priapism in SCA is associated with higher hemolytic rates and show for the first time that this complication is also associated with higher RBC aggregate strength and lower RBC deformability.
Assuntos
Anemia Falciforme/sangue , Agregação Eritrocítica/fisiologia , Deformação Eritrocítica/fisiologia , Eritrócitos/patologia , Hemólise/fisiologia , Priapismo/sangue , Adulto , Anemia Falciforme/patologia , Biomarcadores/sangue , Viscosidade Sanguínea/fisiologia , Hemorreologia/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Priapismo/patologia , Estudos Prospectivos , Reticulócitos/patologiaRESUMO
PURPOSE: To examine how the ischemia-reperfusion injury of latissimus dorsi-cutaneous maximus (LDCM) musculocutaneous flap affects the microcirculatory (flap's skin surface) and hemorheological parameters, and whether an intraoperative deterioration would predictively suggest flap failure in the postoperative period. METHODS: Ten healthy male rats were subjected to the study. In Group I the left flap was sutured back after 2-hour, while the contralateral side was right after its elevation. In Group II the same technique was applied, but the pedicle of the left flap was atraumatically clamped for 2-hour. The contralateral side was left intact. On the flap skin surface laser Doppler tissue flowmetry measurements were done before and after and during the protocols applied in the groups. Microcirculatory and hemorheological examinations were done postoperatively. RESULTS: The microcirculatory parameters significantly decreased during immobilization and ischemia. Afterwards, all the regions showed normalization. In the retrospective analysis there was a prominent difference between the microcirculatory parameters of necrotic and survived flap during the early postoperative days (1-3) in Group II. Erythrocyte aggregation and deformability showed only slight differences. CONCLUSIONS: Two-hour ischemia and reperfusion caused deterioration in latissimus dorsi-cutaneous maximus flap microcirculation. Predicting the possible postoperative complication, the intraoperative laser Doppler measurement can be informative.
Assuntos
Hemorreologia/fisiologia , Microcirculação/fisiologia , Retalho Miocutâneo/irrigação sanguínea , Traumatismo por Reperfusão/fisiopatologia , Pele/irrigação sanguínea , Músculos Superficiais do Dorso/irrigação sanguínea , Animais , Procedimentos Cirúrgicos Dermatológicos , Modelos Animais de Doenças , Período Intraoperatório , Fluxometria por Laser-Doppler , Masculino , Retalho Miocutâneo/patologia , Período Pós-Operatório , Distribuição Aleatória , Ratos , Pele/patologia , Transplante de Pele/métodos , Músculos Superficiais do Dorso/patologia , Fatores de TempoRESUMO
PURPOSE:To examine how the ischemia-reperfusion injury of latissimus dorsi-cutaneous maximus (LDCM) musculocutaneous flap affects the microcirculatory (flap's skin surface) and hemorheological parameters, and whether an intraoperative deterioration would predictively suggest flap failure in the postoperative period.METHODS: Ten healthy male rats were subjected to the study. In Group I the left flap was sutured back after 2-hour, while the contralateral side was right after its elevation. In Group II the same technique was applied, but the pedicle of the left flap was atraumatically clamped for 2-hour. The contralateral side was left intact. On the flap skin surface laser Doppler tissue flowmetry measurements were done before and after and during the protocols applied in the groups. Microcirculatory and hemorheological examinations were done postoperatively.RESULTS: The microcirculatory parameters significantly decreased during immobilization and ischemia. Afterwards, all the regions showed normalization. In the retrospective analysis there was a prominent difference between the microcirculatory parameters of necrotic and survived flap during the early postoperative days (1-3) in Group II. Erythrocyte aggregation and deformability showed only slight differences.CONCLUSIONS: Two-hour ischemia and reperfusion caused deterioration in latissimus dorsi-cutaneous maximus flap microcirculation. Predicting the possible postoperative complication, the intraoperative laser Doppler measurement can be informative.
Assuntos
Animais , Masculino , Ratos , Hemorreologia/fisiologia , Microcirculação/fisiologia , Retalho Miocutâneo/irrigação sanguínea , Traumatismo por Reperfusão/fisiopatologia , Pele/irrigação sanguínea , Músculos Superficiais do Dorso/irrigação sanguínea , Procedimentos Cirúrgicos Dermatológicos , Modelos Animais de Doenças , Período Intraoperatório , Fluxometria por Laser-Doppler , Retalho Miocutâneo/patologia , Período Pós-Operatório , Distribuição Aleatória , Transplante de Pele/métodos , Pele/patologia , Músculos Superficiais do Dorso/patologia , Fatores de TempoRESUMO
To examine how the ischemia-reperfusion injury of latissimus dorsi-cutaneous maximus (LDCM) musculocutaneous flap affects the microcirculatory (flap's skin surface) and hemorheological parameters, and whether an intraoperative deterioration would predictively suggest flap failure in the postoperative period. Ten healthy male rats were subjected to the study. In Group I the left flap was sutured back after 2-hour, while the contralateral side was right after its elevation. In Group II the same technique was applied, but the pedicle of the left flap was atraumatically clamped for 2-hour. The contralateral side was left intact. On the flap skin surface laser Doppler tissue flowmetry measurements were done before and after and during the protocols applied in the groups. Microcirculatory and hemorheological examinations were done postoperatively. The microcirculatory parameters significantly decreased during immobilization and ischemia. Afterwards, all the regions showed normalization. In the retrospective analysis there was a prominent difference between the microcirculatory parameters of necrotic and survived flap during the early postoperative days (1-3) in Group II. Erythrocyte aggregation and deformability showed only slight differences.CONCLUSIONS: Two-hour ischemia and reperfusion caused deterioration in latissimus dorsi-cutaneous maximus flap microcirculation. Predicting the possible postoperative complication, the intraoperative laser Doppler measurement can be informative.(AU)
Assuntos
Animais , Masculino , Ratos , Hemorreologia/fisiologia , Microcirculação/fisiologia , Retalho Miocutâneo/irrigação sanguínea , Traumatismo por Reperfusão/fisiopatologia , Pele/irrigação sanguínea , Músculos Superficiais do Dorso/irrigação sanguínea , Procedimentos Cirúrgicos Dermatológicos , Modelos Animais de Doenças , Período Intraoperatório , Fluxometria por Laser-Doppler , Retalho Miocutâneo/patologia , Período Pós-Operatório , Distribuição Aleatória , Pele/patologia , Transplante de Pele/métodos , Músculos Superficiais do Dorso/patologia , Fatores de TempoRESUMO
Background: central nervous system (CNS) hyperperfusion is one of the events that constitute the pathophysiological basis for the clinical manifestations and complications of pre-eclampsia (PE). Detecting the increased flow in the CNS through Doppler flowmetry of the ophthalmic artery might precede the clinical onset of PE and could be used as a marker for subsequent development of PE. Objective: to evaluate the ophthalmic artery resistive index (OARI) values in the second trimester of pregnancy for prediction of the clinical manifestations of PE. Objective: to evaluate the ophthalmic artery resistive index (OARI) values in the second trimester of pregnancy for prediction of the clinical manifestations of PE. Methods: a total of 73 patients with risk factors for the development of PE were selected from the prenatal service at the HC-UFMG. They were submitted to ophthalmic artery Doppler flowmetry between 24 and 28 weeks of pregnancy and monitored until the end of the pregnancy to verify the occurrence of PE. ROC curves were created to determine the predictive characteristics of the OARI. Results: fourteen of the patients selected developed PE and 59 remained normotensive until the postpartum period. Patients with subsequent development of PE presented OARI values lower than patients that remained normotensive (0.682±0.028 X 0.700±0.029, p=0.044). Considering the development of PE as an outcome, the area under the OARI curve was 0.694 (CI 0.543 to 0.845), with no points obtaining good values of sensitivity or specificity. Conclusion: Doppler flowmetry of ophthalmic arteries between 24 and 28 weeks of pregnancy did not present itself as a good exam for predicting PE. .
Introdução: a hiperperfusão do sistema nervoso central (SNC) é um dos eventos que constitui substrato fisiopatológico para as manifestações clínicas e complicações da pré-eclâmpsia (PE). O fluxo aumentado no SNC, detectado por meio da dopplerfluxometria de artérias oftálmicas, poderia anteceder as manifestações clínicas da PE e, consequentemente, ser utilizado como marcador de subsequente desenvolvimento de PE. Objectivo: avaliar os valores do índice de resistência das artérias oftálmicas (Irao) no segundo trimestre gestacional para a predição das manifestações clínicas da PE. Métodos: pacientes com fatores de risco para desenvolvimento de PE foram selecionadas no serviço de pré-natal do Hospital das Clínicas da Universidade Federal de Minas Gerais (HC-UFMG). Elas foram submetidas à dopplerfluxometria de artérias oftálmicas entre 24 e 28 semanas de gestação e acompanhadas até o final da gestação para averiguar a ocorrência de PE. Curvas ROC foram criadas para determinar as características preditivas do Irao. Resultados: das pacientes selecionadas, 14 desenvolveram PE e 59 mantiveram-se normotensas até o puerpério. Pacientes com subsequente desenvolvimento de PE apresentaram valores de Irao menores do que pacientes que se mantiveram normotensas (0,682±0,028 vs. 0,700±0,029, p=0,044). Ao considerar o desenvolvimento de PE como desfecho, a área sobre a curva do Irao foi de 0,694 (IC 0,543-0,845), sem pontos com bons valores de sensibilidade ou especificidade. Conclusão: a dopplerfluxometria de artérias oftálmicas entre 24 e 28 semanas de gestação não se demonstrou um bom exame para a predição de PE. .
Assuntos
Adulto , Feminino , Humanos , Gravidez , Adulto Jovem , Hemorreologia/fisiologia , Artéria Oftálmica/fisiologia , Pré-Eclâmpsia/diagnóstico , Ultrassonografia Doppler em Cores/métodos , Pressão Sanguínea/fisiologia , Idade Gestacional , Artéria Oftálmica , Valor Preditivo dos Testes , Segundo Trimestre da Gravidez , Prognóstico , Curva ROC , Fatores de Risco , Sensibilidade e Especificidade , Resistência Vascular/fisiologiaRESUMO
BACKGROUND: central nervous system (CNS) hyperperfusion is one of the events that constitute the pathophysiological basis for the clinical manifestations and complications of pre-eclampsia (PE). Detecting the increased flow in the CNS through Doppler flowmetry of the ophthalmic artery might precede the clinical onset of PE and could be used as a marker for subsequent development of PE. OBJECTIVE: to evaluate the ophthalmic artery resistive index (OARI) values in the second trimester of pregnancy for prediction of the clinical manifestations of PE. OBJECTIVE: to evaluate the ophthalmic artery resistive index (OARI) values in the second trimester of pregnancy for prediction of the clinical manifestations of PE. METHODS: a total of 73 patients with risk factors for the development of PE were selected from the prenatal service at the HC-UFMG. They were submitted to ophthalmic artery Doppler flowmetry between 24 and 28 weeks of pregnancy and monitored until the end of the pregnancy to verify the occurrence of PE. ROC curves were created to determine the predictive characteristics of the OARI. RESULTS: fourteen of the patients selected developed PE and 59 remained normotensive until the postpartum period. Patients with subsequent development of PE presented OARI values lower than patients that remained normotensive (0.682 ± 0.028 X 0.700 ± 0.029, p = 0.044). Considering the development of PE as an outcome, the area under the OARI curve was 0.694 (CI 0.543 to 0.845), with no points obtaining good values of sensitivity or specificity. CONCLUSION: Doppler flowmetry of ophthalmic arteries between 24 and 28 weeks of pregnancy did not present itself as a good exam for predicting PE.
Assuntos
Hemorreologia/fisiologia , Artéria Oftálmica/fisiologia , Pré-Eclâmpsia/diagnóstico , Ultrassonografia Doppler em Cores/métodos , Adulto , Pressão Sanguínea/fisiologia , Feminino , Idade Gestacional , Humanos , Artéria Oftálmica/diagnóstico por imagem , Valor Preditivo dos Testes , Gravidez , Segundo Trimestre da Gravidez , Prognóstico , Curva ROC , Fatores de Risco , Sensibilidade e Especificidade , Resistência Vascular/fisiologia , Adulto JovemRESUMO
We analyze the effect that the geometrical place of anastomosis in the circulatory tree has on blood flow. We introduce an idealized model that consists of a symmetric network for the arterial and venous vascular trees. We consider that the network contains a viscoelastic fluid with the rheological characteristics of blood, and analyze the network hydrodynamic response to a time-dependent periodic pressure gradient. This response is a measurement of the resistance to flow: the larger the response, the smaller the resistance to flow. We find that for networks whose vessels have the same radius and length, the outer the level of the branching tree in which anastomosis occurs, the larger the network response. Moreover, when anastomosis is incorporated in the form of bypasses that bridge vessels at different bifurcation levels, the further apart are the levels bridged by the bypass, the larger the response is. Furthermore, we apply the model to the available information for the dog circulatory system and find that the effect that anastomosis causes at different bifurcation levels is strongly determined by the structure of the underlying network without anastomosis. We rationalize our results by introducing two idealized models and approximated analytical expressions that allow us to argue that, to a large extent, the response of the network with anastomosis is determined locally. We have also considered the influence of the myogenic effect. This one has a large quantitative impact on the network response. However, the qualitative behavior of the network response with anastomosis is the same with or without consideration of the myogenic effect. That is, it depends on the structure that the underlying vessel network has in a small neighborhood around the place where anastomosis occurs. This implies that whenever there is an underlying tree-like network in an in vivo vasculature, our model is able to interpret the anastomotic effect.
Assuntos
Vasos Sanguíneos/fisiologia , Hemorreologia/fisiologia , Tecido Adiposo/fisiologia , Anastomose Cirúrgica , Animais , Arteríolas/fisiologia , Cricetinae , Cães , Hidrodinâmica , Modelos Cardiovasculares , Desenvolvimento Muscular/fisiologia , Ratos , Fatores de TempoRESUMO
Previous studies have shown that A. lumbricoides extracts capture sialic acid (SA) from human red blood cells (RBC). The aim of this work was to study hemorheological alterations in vitro caused by parasite larvae. The biorheological action of three larva concentrates of first and second larval stage on group O erythrocytes was analyzed by incubating the erythrocyte packed together with an equal volume of larvae (treated RBC) and PBS (control RBC). Distribution and parameters of aggregation (digital image analysis), aggregation kinetics (erythroaggregameter), and viscoelasticity (erythrodeformeter) were measured. The digital image analysis showed that all the larvae diminished the isolated cells percentage and increased the size of the formed aggregates. The aggregate formation velocity was lower in the treated than in the control. The deformability index (ID) values of treated RBC did not present variations with respect to those of the control, but a decrease in the erythrocyte elastic modulus (µ(m)) and membrane surface viscosity (η(m)) values was observed, indicating that the larvae not only induced a diminution in the membrane surface viscosity of RBC but also altered the dynamic viscoelasticity of the membrane. Experiments carried out in vitro support the conclusion that the contact between larvae and RBC produces hemorheological alterations.
Assuntos
Ascaris lumbricoides/crescimento & desenvolvimento , Deformação Eritrocítica/fisiologia , Eritrócitos/fisiologia , Hemorreologia/fisiologia , Animais , Elasticidade , Agregação Eritrocítica/fisiologia , Membrana Eritrocítica/metabolismo , Membrana Eritrocítica/parasitologia , Membrana Eritrocítica/fisiologia , Eritrócitos/parasitologia , Interações Hospedeiro-Parasita , Humanos , Cinética , Larva/fisiologia , Ácido N-Acetilneuramínico/metabolismo , ViscosidadeRESUMO
OBJETIVO: Avaliar a perviedade dos enxertos no intraoperatório e identificar enxertos com risco de oclusão precoce. MÉTODOS: Cinquenta e quatro pacientes foram submetidos à revascularização do miocárdio e foi utilizado o fluxômetro (Medtronic Medi-Stim) que utiliza o método de tempo de trânsito (TTFM) para avaliação do fluxo nos enxertos. Três pacientes tinham lesão de tronco de artéria coronária esquerda e 48 apresentavam função ventricular normal ou pouco comprometida. RESULTADOS: A mortalidade hospitalar foi de dois (3,7%) pacientes, um por trombose mesentérica e outro por choque cardiogênico. Dezessete (31,4%) pacientes foram operados sem circulação extracorpórea (CEC). O fluxo no enxerto arterial variou de 8 a 106 ml/min, com média de 31,14 ml/min, e nos enxertos venosos de 9 a 149 ml/min, com média de 50,42 ml/min. CONCLUSÃO: O fluxômetro representa maior segurança para o cirurgião e para o paciente. Até mesmo sob o aspecto legal essa documentação dos enxertos pérvios evitará questionamentos futuros.
OBJECTIVE: To evaluate intraoperative graft patency and identify grafts under risk of early occlusion. METHODS: Fifty four patients were submitted to coronary artery bypass surgery and the graft flow was assessed by the Flowmeter (Medtronic Medistim), which utilizes the TTFM method. Three patients had left main disease and 48 had normal or mildly reduced left ventricular function. RESULTS: In hospital mortality was 3.7% (two patients), one for mesenteric thrombosis and one due to cardiogenic chock. Seventeen patients (34%) were submitted to off pump CABG. Arterial Graft flow measures ranged from 8 to 106 ml/min (average 31.14 ml/min), and venous grafts flow ranged from 9 to 149 ml/min (average 50.42 ml/min). CONCLUSION: Flowmeter use represents higher safety both for patients and surgeons. Even under legal aspects, the documentation provided by the device can avoid future questionings.
Assuntos
Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Ponte de Artéria Coronária/instrumentação , Circulação Coronária/fisiologia , Fluxômetros , Hemorreologia/fisiologia , Monitorização Intraoperatória/instrumentação , Ponte de Artéria Coronária/métodos , Mortalidade Hospitalar , Período Intraoperatório , Monitorização Intraoperatória/métodos , Estatísticas não Paramétricas , Fatores de Tempo , Resultado do TratamentoRESUMO
OBJECTIVE: To evaluate intraoperative graft patency and identify grafts under risk of early occlusion. METHODS: Fifty four patients were submitted to coronary artery bypass surgery and the graft flow was assessed by the Flowmeter (Medtronic Medistim), which utilizes the TTFM method. Three patients had left main disease and 48 had normal or mildly reduced left ventricular function. RESULTS: In hospital mortality was 3.7% (two patients), one for mesenteric thrombosis and one due to cardiogenic chock. Seventeen patients (34%) were submitted to off pump CABG. Arterial Graft flow measures ranged from 8 to 106 ml/min (average 31.14 ml/min), and venous grafts flow ranged from 9 to 149 ml/min (average 50.42 ml/min). CONCLUSION: Flowmeter use represents higher safety both for patients and surgeons. Even under legal aspects, the documentation provided by the device can avoid future questionings.
Assuntos
Ponte de Artéria Coronária/instrumentação , Circulação Coronária/fisiologia , Fluxômetros , Hemorreologia/fisiologia , Monitorização Intraoperatória/instrumentação , Adulto , Idoso , Idoso de 80 Anos ou mais , Ponte de Artéria Coronária/métodos , Feminino , Mortalidade Hospitalar , Humanos , Período Intraoperatório , Masculino , Pessoa de Meia-Idade , Monitorização Intraoperatória/métodos , Estatísticas não Paramétricas , Fatores de Tempo , Resultado do TratamentoRESUMO
The professional activity that the cardiovascular surgeon performs is much more than a simple gesture to mechanically operate the patient's heart. There is in every act of intraoperative most notions of physiology and physics than we generally realize. This paper discusses, in the light of mathematics, on the dynamics of fluids, ie blood, focused on invasive measurements of blood pressure, the effect of vessel size on its internal resistance and the flow passing through it in conversion of various units of measurements of pressure and resistance, blood viscosity and its relationship to the vessel, hemodilution, differences in laminar and turbulent flow, velocity and blood pressure and wall tension after a stenosis and the origin of poststenotic aneurysm. This study is not to enable the reader to the knowledge of all physics, but to show it as a useful tool in explaining phenomena known in the routine of cardiovascular surgery.
Assuntos
Procedimentos Cirúrgicos Cardiovasculares/educação , Hemodinâmica/fisiologia , Física , Algoritmos , Velocidade do Fluxo Sanguíneo , Hematócrito , Hemorreologia/fisiologia , Humanos , Pressão Hidrostática , Resistência Vascular/fisiologiaRESUMO
This study compared the hemorheological responses of a group of sickle cell trait (SCT) carriers with those of a control (Cont) group in response to 40 min of submaximal exercise (exercise intensity, 55% aerobic peak power) performed in two conditions: one with water offered ad libitum, i.e., the hydration (Hyd) condition, and one without water, i.e., the dehydration (Dehyd) condition. Blood and plasma viscosities, as well as red blood cell rigidity, were determined at rest, at the end of exercise, and at 2 h recovery with a cone plate viscometer at high shear rate and 37 degrees C. The SCT and Cont groups lost 1 +/- 0.7 and 1.6 +/- 0.6 kg of body weight, respectively, in the Dehyd condition, indicating a significant effect of water deprivation compared with the Hyd condition, in which body weight remained unchanged. Plasma viscosity increased with exercise and returned to baseline during recovery independently of the group and condition. As previously demonstrated, resting blood viscosity was greater in the SCT carriers than in the Cont group. Blood viscosity increased by the end of exercise and returned to baseline at 2 h recovery in the Cont group in both conditions. The blood viscosity of SCT carriers did not change in response to exercise in the Dehyd condition and remained elevated at 2 h recovery. This extended hyperviscosity, in association with other biological changes induced by exercise, could be considered as a risk factor for exercise-related events in SCT carriers, similar to vasoocclusive crises, notably during the recovery. In contrast, the Hyd condition normalized the hyperviscosity and red blood cell rigidity of the SCT carriers, with blood viscosity values reaching the same lower values as those found in the Cont group during the recovery. Adequate hydration of SCT carriers should be strongly promoted to reduce the clinical risk associated with potential hyperviscosity complications.
Assuntos
Desidratação/sangue , Exercício Físico/fisiologia , Hemorreologia/fisiologia , Traço Falciforme/sangue , Viscosidade Sanguínea/fisiologia , Desidratação/fisiopatologia , Feminino , Humanos , Masculino , Traço Falciforme/fisiopatologiaRESUMO
A atividade profissional que o cirurgião cardiovascular executa é muito mais do que um simples gesto mecanizado de operar um coração doente. Há em cada ato do intraoperatório mais noções de fisiologia e física do que geralmente nos damos conta. O presente trabalho discorre, à luz da matemática, acerca da dinâmica dos fluídos, ou seja, do sangue, com enfoque nas medidas invasivas de pressão arterial, do efeito do diâmetro do vaso sobre sua resistência interna e do fluxo que passa por ele, na conversão de diversas unidades de medidas de pressão e resistência, viscosidade sanguínea e suas relações no vaso, hemodiluição, diferenças de fluxo laminar e turbulento, velocidade e pressão do sangue e a tensão da parede após uma estenose e a origem do aneurisma pós-estenótico. O objetivo do trabalho não é de habilitar o leitor no conhecimento da física, mas apresentá-la como ferramenta útil na explicação de fenômenos conhecidos na rotina do cirurgião cardiovascular.
The professional activity that the cardiovascular surgeon performs is much more than a simple gesture to mechanically operate the patient's heart. There is in every act of intraoperative most notions of physiology and physics than we generally realize. This paper discusses, in the light of mathematics, on the dynamics of fluids, ie blood, focused on invasive measurements of blood pressure, the effect of vessel size on its internal resistance and the flow passing through it in conversion of various units of measurements of pressure and resistance, blood viscosity and its relationship to the vessel, hemodilution, differences in laminar and turbulent flow, velocity and blood pressure and wall tension after a stenosis and the origin of poststenotic aneurysm. This study is not to enable the reader to the knowledge of all physics, but to show it as a useful tool in explaining phenomena known in the routine of cardiovascular surgery.
Assuntos
Humanos , Procedimentos Cirúrgicos Cardiovasculares/educação , Hemodinâmica/fisiologia , Física , Algoritmos , Velocidade do Fluxo Sanguíneo , Hematócrito , Pressão Hidrostática , Hemorreologia/fisiologia , Resistência Vascular/fisiologiaRESUMO
Aerobic performance is dependent on both cardio-respiratory and peripheral factors with hemodynamic parameters playing a major role. However, whether blood rheology might affect aerobic performance through an effect on hemodynamic factors is not known. The aim of the present study was to assess the relationships between hemodynamic, hemorheological and metabolic parameters in response to a sub-maximal cycling exercise protocol consisting of three successive levels of nine min duration (50, 100 and 150 W). Ten young sportsmen participated in the present study. Mean arterial pressure (MAP) was measured manually, with thoracic impedance used to monitor cardiac output (Qc): systemic vascular resistance (SVR) was then calculated. Whole blood viscosity (etab) was measured and used to calculate systemic vascular hindrance. Hematocrit (Hct) was determined by micro-centrifugation and red blood cell (RBC) deformability (EI) was determined by ecktacytometry. A breath-by-breath gas analyzer was used to measure oxygen uptake (VO2); the Fick equation was used to calculate arterio-venous oxygen difference [(a-v)O(2)] from VO(2) and Qc. All measurements were performed at rest, during exercise and during recovery. Compared to baseline, Qc, MAP, Hct, EI, VO(2), and (a-v)O(2) increased during exercise. etab increased above baseline only at 150 W and remained elevated during recovery; the increase in etab during the last level of exercise was associated with a decrease of SVR and systemic vascular hindrance. There was a significant negative correlation between EI and SVR (r=-0.35, p<0.01) and a significant positive relationship between EI and (a-v)O(2) (r=0.35, p<0.01) and between EI and VO(2) (r=0.37, p<0.01) across all exercise workloads, thus suggesting a potential role for RBC deformability as a factor affecting aerobic performance via oxygen delivery to tissues. These data lend support to the concept that hemorheological parameters may contribute to hemodynamic and cardio-respiratory adaptations in response to exercise in moderately trained sportsmen.
Assuntos
Exercício Físico/fisiologia , Hemodinâmica/fisiologia , Hemorreologia/fisiologia , Viscosidade Sanguínea/fisiologia , Deformação Eritrocítica/fisiologia , Teste de Esforço/métodos , Humanos , Masculino , Consumo de Oxigênio/fisiologia , Oxiemoglobinas/metabolismo , Resistência Vascular/fisiologia , Adulto JovemRESUMO
In this work, we study theoretically the unloading of oxygen from a hemoglobin molecule to the wall of a typical capillary vessel, considering that the hemoglobin under pathological conditions, obeys the rheological Maxwell model. Based on recent experimental evidences in hypertension, we consider that the red blood cells (RBCs) are composed by a single continuous medium in contrast with the classical particulate or discrete RBC models, which are only valid under normal physiological conditions. The analysis considers the hemodynamic interactions between the plasma and the hemoglobin, both circulating in a long horizontal capillary. We apply numerical and analytical methods to obtain the main fluid-dynamic characteristics for both fluids in the limit of low Reynolds and Womersley numbers. A diffusion boundary layer formulation for the oxygen transport in the combined plasma-hemoglobin core region is presented. The main aspects derived are the time and spatial evolution of the membrane. The hemoglobin and plasma velocities and the pressure distributions are shown. For the oxygen unloading the results are the oxy-hemoglobin saturation, the oxygen flux and the oxygen concentration in the cell-free plasma layer. The volume fraction of red blood cells and the Strouhal number have a great influence on the hemodynamic interactions.