RESUMO
AbstractBackground:Right ventricular (RV) afterload is an important risk factor for post-heart transplantation (HTx) mortality, and it results from the interaction between pulmonary vascular resistance (PVR) and pulmonary compliance (CPA). Their product, the RC time, is believed to be constant. An exception is observed in pulmonary hypertension because of elevated left ventricular (LV) filling pressures.Objective:Using HTx as a model for chronic lowering of LV filling pressures, our aim was to assess the variations in RV afterload components after transplantation.Methods:We retrospectively studied 159 patients with right heart catheterization before and after HTx. The effect of Htx on hemodynamic variables was assessed.Results:Most of the patients were male (76%), and the mean age was 53 ± 12 years. HTx had a significant effect on the hemodynamics, with normalization of the LV and RV filling pressures and a significant increase in cardiac output and heart rate (HR). The PVR decreased by 56% and CPA increased by 86%. The RC time did not change significantly, instead of increasing secondary to pulmonary wedge pressure (PWP) normalization after HTx as expected. The expected increase in RC time with PWP lowering was offset by the increase in HR (because of autonomic denervation of the heart). This effect was independent from the decrease of PWP.Conclusion:The RC time remained unchanged after HTx, notwithstanding the fact that pulmonary capillary wedge pressure significantly decreased. An increased HR may have an important effect on RC time and RV afterload. Studying these interactions may be of value to the assessment of HTx candidates and explaining early RV failure after HTx.
ResumoFundamento:A pós-carga do ventrículo direito (VD) é um fator de risco importante para avaliar a mortalidade decorrente de transplante cardíaco (HTx) e resulta da interação entre a resistência vascular pulmonar (RVP) e a complacência pulmonar (CPA). Acredita-se que o produto da interação, o RC-time, seja constante. Entretanto, é exceção a hipertensão pulmonar devido às elevadas pressões de preenchimento do ventrículo esquerdo (VE).Objetivos:Ao utilizar o HTx como modelo para redução crônica das pressões de preenchimento do VE, nosso objetivo foi avaliar as variações nos componentes pós-carga do VD após o transplante.Métodos:Foram estudados, retrospectivamente, 159 pacientes com cateterismo cardíaco direito realizado antes e após o HTx. O impacto do HTx nas variáveis hemodinâmicas foi avaliado.Resultados:A maioria dos pacientes foi do sexo masculino (76%) e a média de idade foi 53 ± 12 anos. O HTx teve um efeito significativo na hemodinâmica, com normalização do VE e das pressões de preenchimento de VD e no aumento significativo do débito cardíaco e da freqüência cardíaca (FC). A RVP diminuiu 56% e a CPA aumentou 86%. Em vez de aumentar como era esperado, o RC-time não alterou significativamente e teve papel secundário em relação à normalização da pressão capilar pulmonar (PECP) após o HTx. O aumento esperado no RC timecom PWP reduzido foi atenuado pelo aumento da FC (devido à denervação autonômica do coração). Esse efeito ocorreu independentemente da diminuição da PCPConclusões:O RC-time permaneceu inalterado após HTx, entretanto a PECP diminuiu significativamente. O aumento da FC pode ter impacto importante no RC-time e na pós-carga do VD. O estudo dessas interações pode ser de grande valor para avaliar os candidatos HTx e explicar a falência do VD ocorrida logo após o HTx.
Assuntos
Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Resistência Capilar/fisiologia , Transplante de Coração/métodos , Complacência Pulmonar/fisiologia , Pressão Propulsora Pulmonar/fisiologia , Função Ventricular/fisiologia , Análise de Variância , Frequência Cardíaca/fisiologia , Período Pós-Operatório , Valores de Referência , Estudos Retrospectivos , Fatores de TempoRESUMO
BACKGROUND: Right ventricular (RV) afterload is an important risk factor for post-heart transplantation (HTx) mortality, and it results from the interaction between pulmonary vascular resistance (PVR) and pulmonary compliance (CPA). Their product, the RC time, is believed to be constant. An exception is observed in pulmonary hypertension because of elevated left ventricular (LV) filling pressures. OBJECTIVE: Using HTx as a model for chronic lowering of LV filling pressures, our aim was to assess the variations in RV afterload components after transplantation. METHODS: We retrospectively studied 159 patients with right heart catheterization before and after HTx. The effect of Htx on hemodynamic variables was assessed. RESULTS: Most of the patients were male (76%), and the mean age was 53 ± 12 years. HTx had a significant effect on the hemodynamics, with normalization of the LV and RV filling pressures and a significant increase in cardiac output and heart rate (HR). The PVR decreased by 56% and CPA increased by 86%. The RC time did not change significantly, instead of increasing secondary to pulmonary wedge pressure (PWP) normalization after HTx as expected. The expected increase in RC time with PWP lowering was offset by the increase in HR (because of autonomic denervation of the heart). This effect was independent from the decrease of PWP. CONCLUSION: The RC time remained unchanged after HTx, notwithstanding the fact that pulmonary capillary wedge pressure significantly decreased. An increased HR may have an important effect on RC time and RV afterload. Studying these interactions may be of value to the assessment of HTx candidates and explaining early RV failure after HTx.
Assuntos
Resistência Capilar/fisiologia , Transplante de Coração/métodos , Complacência Pulmonar/fisiologia , Pressão Propulsora Pulmonar/fisiologia , Função Ventricular/fisiologia , Adulto , Idoso , Análise de Variância , Feminino , Frequência Cardíaca/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Período Pós-Operatório , Valores de Referência , Estudos Retrospectivos , Fatores de TempoRESUMO
OBJECTIVES: To improve algorithms for the identification of children at risk of dying of malaria in endemic areas. STUDY DESIGN: In a prospective study of 2446 children with severe and complicated malaria admitted to a tertiary referral center in Ghana, West Africa, 12 clinical and laboratory signs were evaluated as indicators of death. RESULTS: A prolonged (> 2 seconds) capillary refill time (pCRT) was identified as an independent prognostic indicator of death along with acidosis, coma, and respiratory distress. Among the clinical signs, pCRT increased the risk of dying from 4-fold to 11-fold when present in addition to coma and respiratory distress. CONCLUSIONS: The recognition of pCRT as an independent indicator of death justifies its inclusion as a defining criterion of severe and complicated malaria and improves the use of clinical examinations in the triage of patients with malaria. As pCRT has been shown to reflect circulatory disturbances in children, it should be included in upcoming studies as a possible sign to indicate the need for intravenous fluid administration.
Assuntos
Resistência Capilar , Malária/fisiopatologia , Acidose/mortalidade , Acidose/fisiopatologia , Adolescente , Adulto , Idoso , Análise de Variância , Anemia/mortalidade , Anemia/fisiopatologia , Biomarcadores/sangue , Criança , Pré-Escolar , Coma/mortalidade , Coma/fisiopatologia , Feminino , Gana/epidemiologia , Frequência Cardíaca , Humanos , Malária/mortalidade , Masculino , Pessoa de Meia-Idade , Parasitemia/mortalidade , Parasitemia/fisiopatologia , Prognóstico , Estudos Prospectivos , Insuficiência Respiratória/mortalidade , Insuficiência Respiratória/fisiopatologia , Fatores de Risco , Sensibilidade e Especificidade , Índice de Gravidade de Doença , Taxa de Sobrevida , Fatores de TempoRESUMO
Seventeen patients with diagnosis of acute myocardial infarction with right ventricular extension were studied. All of them had evidence of contractile impairment of the right ventricle as shown by elevated filling pressure of the right ventricle, low systolic pulmonary pressure and low left ventricular filling pressure and cardiac output. These patients were treated with fluid infusion into the pulmonary artery besides other treatment measures for myocardial infarction in order to improve the filling pressure of the left ventricle and the cardiac output without stressing the right ventricle. The results obtained with this approach, which was maintained for 22 hours, showed a significant improvement in the stroke work indices of both ventricles and also in the cardiac output with a decrease in peripheral resistence without ever loading the ventricles. We analyze the physiological basis for using this procedure and also the complications that can occur. Our results show that the infusion of fluid into the pulmonary artery improves the hemodynamic situation of these patients and protects a damaged right ventricle.
Assuntos
Glucose/uso terapêutico , Infarto do Miocárdio/terapia , Artéria Pulmonar , Idoso , Pressão Sanguínea , Resistência Capilar , Débito Cardíaco , Feminino , Glucose/administração & dosagem , Insuficiência Cardíaca/prevenção & controle , Ventrículos do Coração/fisiopatologia , Humanos , Infusões Intra-Arteriais , Masculino , Pessoa de Meia-Idade , Infarto do Miocárdio/fisiopatologia , Volume SistólicoRESUMO
The deformability of the red blood cell was analysed into viscous, elastic and geometrical components and shown to be unidentifiable as a single measurable physical property. The measurement of deformability was then atttempted in three ways. Capillary traversal times of red blood cells were measured as an index of deformability. Osmotic swelling was shown to decrease deformability. Suggestions were made for overcoming the technical difficulties so as to allow for routine use of the method. The method seems to have considerable potential for investigating the effects of changes in deformability on flow in the micro-circulation. The relaxation time associated with recovery of shape (and orientation) of red cells was measured as an index of deformability. The results suggest that the recovery of shape is very rapid, < 1 s, and that thereafter the relaxation is of orientation and the cell behaves as a rigid disc. The method appears not to be useful. Measurements of apparent viscosity, shear rate, and cell volume fraction were made for suspensions of red cells and elastic and viscous parameters obtained based on modelling of the red cell as a liquid drop and as a viscoelastic sphere. The viscoelastic sphere theory was found to be a better description of red blood cell rheology than the liquid drop model, which was found to be unsuitable. Values of bulk cell viscosity and cell rigidity were obtained. The optimal hematocrit method was also employed and in this last method, microviscometry was used to extend the measurements to diseased states. No significant difference between samples from normal and diseased subjects were observed. It was found that the red cell is very fluid; the theory of red cell suspension viscosity undeveloped; and the accuracy of low viscosity microviscometers insufficient to measure small changes in viscosity (AU)