RESUMEN
Studies by electromagnetic flowmetry in acute experiments on cats under conditions of the open thoracic cage and artificial ventilation of the lungs showed that 64% of venous return via the vena cava posterior was realized at the expense of the splanchnic and 36% due to the musculocutaneous vessels (abdominal basin of the caudal vein). Epinephrine (20 µg/kg) increased the contribution of the splanchnic venous blood flow to the increase in the blood flow in the vena cava posterior and reduced the contribution of the musculocutaneous veins throughout the entire duration of systemic reactions: 84% of the blood flow increase in the vena cava posterior was due to the splanchnic and just 16% due to the musculocutaneous blood flow. Norepinephrine (10 µg/kg) resulted in a phase-wise involvement of the studied compartments in blood flow increase in the vena cava posterior. During the initial period of systemic reactions (coinciding with the maximum systemic BP rise) the contribution of the musculocutaneous compartment was 13% higher, while later (by the time of the maximum elevation of venous blood flow in the studied compartments) the contribution of splanchnic veins predominated constituting 89% of venous blood flow in the vena cava posterior. These results indicate that venous blood flow increase in the splanchnic vessels largely determined the formation of changes in the vena cava posterior blood flow in response to catecholamines.
Asunto(s)
Músculos/irrigación sanguínea , Norepinefrina/farmacología , Flujo Sanguíneo Regional , Piel/irrigación sanguínea , Circulación Esplácnica , Venas Cavas/efectos de los fármacos , Animales , Gatos , Norepinefrina/administración & dosificación , Venas Cavas/fisiologíaRESUMEN
Myocardial ischemia caused inhibition of myocardial contractility, increased pressure in the left atrium, reduced cardiac output and reduced systemic blood pressure. The decrease in cardiac output is due to a combination of the myocardial contractility reduction and that of the outflow of blood from the pulmonary vascular bed. Hemodynamic changes in the arterial part of the systemic circulation are accompanied by shifts in its venous part: reduced blood flow in the anterior and posterior caval veins and a decrease in venous return. The determining factor for reducing the flow of venous blood to the heart during myocardial ischemia is a decrease in cardiac output. Myocardial ischemia of the left ventricle is accompanied by a decrease in pressure and blood flow in the pulmonary artery. The data obtained suggest that the degree of reduction of these indicators of pulmonary hemodynamics depends on the elevated pressure in the left atrium resulting from reduction of the left ventricle contractility. The degree of hemodynamic disorders in systemic and pulmonary circulation in myocardial ischemia depends not only on the size of the zone of myocardial ischemia of the left ventricle, but also on the duration of cessation of its blood supply. We suggest that the time factor is a decisive one with respect to severity of hemodynamic disorders occurring only at a certain, critical, size of the zone of myocardial ischemia.
Asunto(s)
Gasto Cardíaco , Ventrículos Cardíacos/fisiopatología , Isquemia Miocárdica/fisiopatología , Circulación Pulmonar , Animales , Velocidad del Flujo Sanguíneo , Presión Sanguínea , Gatos , Arteria Pulmonar/fisiopatologíaRESUMEN
Ischemia of left ventricular myocardium in cats moderated blood flow in the venae cavae and decreased venous return, which leads to a drop of blood flow and blood pressure in the pulmonary artery. Shifts in the right atrial pressure had no effects on changes in venous returns. After elevation of the left atrial pressure, promoted by a decrease in contractility of the left ventricular myocardium, blood pressure in the pulmonary artery decreased to a lesser extent than pulmonary blood flow, but did not correlate with shifts in pulmonary vascular resistance.
Asunto(s)
Pulmón/irrigación sanguínea , Isquemia Miocárdica/fisiopatología , Arteria Pulmonar/fisiopatología , Venas Pulmonares/fisiopatología , Animales , Gatos , Hemodinámica , Flujo Sanguíneo RegionalRESUMEN
Experiments on cats showed that catecholamines produced maximum changes in pulmonary artery blood pressure during 12-16 sec postinjection, while blood flow in this artery attained maximum only to 40 sec postinjection, i.e. changes in blood flow attained maximum and ended later than blood pressure shifts. Intravenous epinephrine produced bidirectional changes in blood pressure, while norepinephrine always elevated blood pressure in the pulmonary artery; pulmonary circulation increased after injection of both catecholamines.
Asunto(s)
Velocidad del Flujo Sanguíneo/efectos de los fármacos , Presión Sanguínea/efectos de los fármacos , Catecolaminas/farmacología , Hemodinámica/efectos de los fármacos , Arteria Pulmonar/efectos de los fármacos , Animales , Gatos , Epinefrina/farmacología , Norepinefrina/farmacología , Simpatomiméticos/farmacologíaRESUMEN
The character and values of changes of the pulmonary and systemic hemodynamics following epinephrine, norepinephrine and angiotensin intravenous injection were studied in acute experiments on the anesthetized cats. After catecholamines injection pulmonary blood flow was always increased, meanwhile pulmonary artery pressure can be elevated (in the most observations) or decreased. In the cases of angiotensin administration the pulmonary blood flow could be augmented or decreased; pulmonary artery pressure had been increased or decreased independently from the character of changes of pulmonary flow. Thus, linear correlation between shifts of the pulmonary artery pressure and pulmonary blood flow had not been revealed. The changes of the pulmonary artery pressure were not correlated with the pulmonary vascular resistance ones; however they had strong relationship with the changes of the left atrial pressure. If the left atrial pressure was decreased the pulmonary artery pressure elevation was less, comparing with its values in experiments, where the left atrial pressure was increased; in the case of depressor shifts of pulmonary artery pressure, the left atrial pressure was also decreased. The character and values of the pulmonary blood flow changes were strongly correlated with the changes of the venous return; however they had no linear correlations with the right and left atrial pressures and pulmonary vascular resistance changes. Thus we concluded, that hemodynanics mechanisms of the pulmonary artery pressure and flow changes following vasoactive pressor drugs injection changes are different.
Asunto(s)
Velocidad del Flujo Sanguíneo/efectos de los fármacos , Pulmón/irrigación sanguínea , Arteria Pulmonar , Resistencia Vascular/efectos de los fármacos , Vasoconstrictores/farmacología , Animales , Presión Sanguínea/efectos de los fármacos , GatosRESUMEN
The character and values of changes of the pulmonary and systemic hemodynamics following neurogenic stimuli application on the cardiovascular system were studied in acute experiments on the anesthetized cats. Vagus nerve stimulation reduced the heart rate and decreased myocardial contractility in result, right and left atrial pressure increased, whereas pulmonary pressure and flow, venous return, cardiac output and venous return decreased. Pulmonary pressure reached maximal level and returned to the initial value earlier than the pulmonary flow. On the contrary, pulmonary pressure, following neurogenic pressor stimuli, reached maximal level and returned to the initial value later than the pulmonary flow; the sign of the changes of the pulmonary pressure could be positive or negative, whereas pulmonary flow were always increased. The venous return did not change, and for this reason it could not cause the increasing of pulmonary flow which was elevated following increasing of the heart rate and myocardial contractility. The shifts of the pulmonary pressure were correlated with the pulmonary resistance those, which were increased after the stellate ganglion stimulation and decreased following carotid reflex; they did not change in case of sciatic nerve stimulation. The shifts of the pulmonary pressure did not depended on the decreased right and left atrial pressures. When the pulmonary flow was always increased, the cardiac output following electrical stimulation of the stellate ganglion and sciatic nerve was elevated, and it was decreased following carotid reflex, i. e. linear correlation between these parameters were not found. Pulmonary and systemic arterial pressure changes were more obvious in case of direct neurogenic stimuli application comparing with reflectory ones; in both cases, the positive chrono- and inotropic cardiac effects were similar.
Asunto(s)
Velocidad del Flujo Sanguíneo , Gasto Cardíaco , Frecuencia Cardíaca , Pulmón/irrigación sanguínea , Contracción Miocárdica , Animales , Presión Sanguínea , Gatos , Estimulación Eléctrica , Nervio Ciático , Ganglio Estrellado , Nervio VagoRESUMEN
Acute experiments on narcotized cats with depressor shifts in the circulatory system induced by acetylcholine and histamine revealed more pronounced decrease in vascular resistance in the brachiocephalic artery in comparison with the thoracic aorta basin. Cardiac output was redistributed between these vascular basins: the bloodflow increased in the brachiocephalic artery and decreased in the thoracic aorta. Hemodynamic shifts in the arterial compartment of the vascular system are presumably essential for changes in the bloodflow in venae cavae.
Asunto(s)
Aorta Torácica/fisiología , Tronco Braquiocefálico/fisiología , Resistencia Vascular , Animales , Presión Sanguínea , GatosRESUMEN
Shifts in right- and left-atrial pressure after administration of acetylcholine, histamine, or isoproterenol to cats were oppositely directed in 69% cases; both parameters decreased in 11% cases (changes were more pronounced in the right atrium) and increased in 20% cases (similar shifts). Changes in the left-atrial pressure persisted for a longer time (compared to those in the right atrium) and their dynamics was similar to that of venous return and cardiac output.
Asunto(s)
Función Atrial/fisiología , Circulación Sanguínea/efectos de los fármacos , Presión Sanguínea/efectos de los fármacos , Gasto Cardíaco/efectos de los fármacos , Fármacos Cardiovasculares/farmacología , Acetilcolina/farmacología , Animales , Función Atrial/efectos de los fármacos , Gatos , Histamina/farmacología , Isoproterenol/farmacología , Factores de TiempoRESUMEN
In acute experiments on anesthetized cats, intravenous injection of the pressor drugs (epinephrine and norepinephrine) and depressor drugs (acetylcholine, histamine, isadrin) caused different changes of right and left atrial pressures. Following catecholamine injection, right atrial pressure decreased in most cases, whereas left atrial pressure increased. In case of injection of the depressor drugs, right atrial pressure increased in most cases, and left atrial pressure decreased. Thus, changes of atrial pressures following intravenous injections of pressor and depressor drugs were reciprocal. The percent changes of the right atrial pressure in case of intravenous injections of pressor drugs were lesser than in the left atrial pressure. In case of intravenous injection of depressor drugs, if both right and left atrial pressures were decreased, then the percent changes of the right atrial pressure were more significant than in the left atrial pressure. If both right and left atrial pressure were increased their percent changes were equal. The increasing of inferior vena cava flow following catecholamine injection was less significant if atrial pressures were increased, whereas in case of depressor drugs injection superior vena cava flow was less significant if atrial pressures were increased. The character of changes of the right and left atrial pressures had no linear correlation with the directions of the shifts of the venous return and cardiac output.
Asunto(s)
Función del Atrio Izquierdo/fisiología , Función del Atrio Derecho/fisiología , Vasoconstrictores/administración & dosificación , Vasodilatadores/administración & dosificación , Presión Venosa/efectos de los fármacos , Animales , Determinación de la Presión Sanguínea , Gatos , Inyecciones Intravenosas , Volumen Sistólico/efectos de los fármacos , Vena Cava Inferior/fisiología , Presión Venosa/fisiologíaRESUMEN
Acute experiments on cats showed that injection of catecholamines induced unidirectional shifts in right and left atrial pressure in 70% cases (these shifts were positive in one half of cats and negative in the other half). In 30% cases, the left and right atrial pressures changed in opposite direction: right atrial pressure decreased, while left atrial pressure increased (19%), or vice versa (11%). The pressure changes in the left atrium had greater amplitude and longer duration compared to those in the right atrium.
Asunto(s)
Función Atrial , Presión Sanguínea/efectos de los fármacos , Catecolaminas/farmacología , Atrios Cardíacos/efectos de los fármacos , Animales , Función Atrial/efectos de los fármacos , Catecolaminas/fisiología , Gatos , Epinefrina/farmacología , Epinefrina/fisiología , Norepinefrina/farmacología , Norepinefrina/fisiologíaRESUMEN
In acute experiments on anesthetized cats, intravenous injection of epinephrine and norepinephrine caused different changes of right and left artrial pressures. These shifts mostly (82%) had similar directions: in these experiments, both right and left atrial pressures could be decreased (I group of animals) or increased (II group). The number of animals in these groups was equal. However, in 18% of the experiments, right atrial pressure was decreased, while left atrial pressure was increased. The changes of the left atrial pressure was, as a rule, more significant as compared with right atrial pressure shifts. In the I group of animals, systolic right atrial pressure was not changed, and systolic left atrial pressure was decreased. In the II group of animals, systolic pressure in both atria was augmented. Diastolic pressure was decreased in both atria in all the animals. When the atrial pressures were decreased, the increases of the superior and inferior vena cava flows, venous return and cardiac output were more significant as compared with animals in which the atrial pressures had been elevated. The changes of the superior and inferior vena cava flows were more obvious in animals following epinephrine injection as compared with animals in which norepinephrine was injected. The right atrial pressure returned to the initial level more rapidly than the left atrial pressure, and the time dynamics of the shifts of the right atrial pressure was similar to that of the superior vena cava flow. The temporal changes of the left atrial pressure were identical to the time changes of the cardiac output. We concluded that character of changes of the mean, systolic, and diastolic right and left atrial pressures following catecholamines injections was not correlated with the direction of venous return and cardiac output shifts, and was depending on intracardiac hemodynamics.
Asunto(s)
Función Atrial/efectos de los fármacos , Epinefrina/farmacología , Hemodinámica/efectos de los fármacos , Norepinefrina/farmacología , Animales , Presión Sanguínea/efectos de los fármacos , Gasto Cardíaco/fisiología , Gatos , Epinefrina/administración & dosificación , Atrios Cardíacos/efectos de los fármacos , Inyecciones Intravenosas , Norepinefrina/administración & dosificación , Vena Cava Inferior/fisiología , Vena Cava Superior/fisiologíaRESUMEN
In acute experiments on anesthetized cats, intravenous injection of the norepinephrine and angiotensin caused different changes of right atrial pressure in intact animals (decreasing--I group, of animals, and increasing--II group). After right and left vagus nerves had been cut, the right atrial pressure in the I group of animals decreased, but its changes were lesser than in intact animals due to slowing down of the increase of the right ventricular myocardial contractility and venous return. The latter was the result of severe diminution of the increase of the superior vena cava flow compared with the intact animals, meanwhile the value of the inferior vena cava flow did not change. In the II group animals after vagotomy and intravenous injection of the noripinephrine and angiotensin the sign of the right atrial pressure became negative, i. e. the direction of its shifts changed to the opposite, compared with intact animals. In this case, the changes of the sign of the right atrial pressure was caused by the removal of the reflectory inhibitory vagal influences on the heart, because the values of the right ventricular myocardial contractility and venous return were the same as in intact animals of the group, due to decreasing of the value of the superior vena cava flow and increasing of the shifts of the inferior vena cava flow. The vagotomy alone caused also different changes (decreasing or increasing) of right atrial pressure following increasing of the right ventricular myocardial contractility, meanwhile the changes of the venous return were insignificant. Direct electrical stimulation of both the right and the left vagus nerves caused the increasing of the right atrial pressure and decreasing of the right ventricular myocardial contractility and venous return. Thus we concluded, that different changes of the right atrial pressure in animals following intravenous injection of the pressor vasoactive drugs could be the result of different manifestations of the vagal afferent impulsation, which has influence on the sympathetic tonic discharges on the vessels of the regions of the superior and inferior vena cava, and the vagal reflectory inhibitory influences on the heart.
Asunto(s)
Angiotensinas/administración & dosificación , Norepinefrina/administración & dosificación , Nervio Vago/fisiología , Vasoconstrictores/administración & dosificación , Función Ventricular , Función Ventricular/fisiología , Animales , Función del Atrio Derecho/efectos de los fármacos , Función del Atrio Derecho/fisiología , Presión Sanguínea/efectos de los fármacos , Presión Sanguínea/fisiología , Gatos , Atrios Cardíacos/inervación , Ventrículos Cardíacos/inervación , Función Ventricular/efectos de los fármacosRESUMEN
Changes of the right atrial pressure, superior and inferior vena cava flows, right ventricular myocardial contractility (first derivate of right ventricular pressure, dP/dt max) following i.v. injection of acetylcholine, histamine and isoproterenol, were studied in acute experiments on anaesthetized mongrel cats with artificial lung ventilation and opened chest. The right atrial pressure in those cases could be increased (I group of animals) or decreased (II group). In maximal shifts of right atrial pressure following acetylcholine injection, the superior vena cava flow increased but the inferior vena cava flow decreased in equal proportion. When the right ventricular myocardial contractility decreased more than the right atrial pressure was augmented, and when the cardiac negative inotropic effect was weak, the right atrial pressure was reduced. After histamine injection in both groups of animals, right ventricular myocardial contractility was increased on the same level, and changes of the inferior vena cava flow were insignificant. The right atrial pressure was elevated following greater increase of superior vena cava flow. Isoproterenol caused the positive cardiac inotropic effect and augmenting of the superior vena cava flow in both groups of animals. The right atrial pressure was elevated if the inferior vena cava flow increased and, on the other hand, when the inferior vena cava flow decreased the right atrial pressure was reduced. Thus different maximal changes of the right atrial pressure following i.v. injection of acetylcholine, histamine and isoproterenol could be explained by different hemodynamic mechanisms of the interaction between superior and inferior vena cava flow shifts and changes of the right ventricular myocardial contractility.
Asunto(s)
Función del Atrio Derecho/efectos de los fármacos , Presión Sanguínea/efectos de los fármacos , Hemodinámica/efectos de los fármacos , Vasodilatadores/farmacología , Acetilcolina/farmacología , Animales , Función del Atrio Derecho/fisiología , Gatos , Hemodinámica/fisiología , Histamina/farmacología , Isoproterenol/farmacología , Contracción Miocárdica/efectos de los fármacosRESUMEN
Experiments on cats treated with nitroglycerin showed dynamic relationship between changes in caval venous flows: blood flow increased in the superior vena cava and decreased in the inferior vena cava. Blood pressure in the right atrium either decreased, or increased. No significant changes in total venous return were observed during maximum shifts in right atrial pressure, while contractility of the right ventricular myocardium usually decreased. Our findings suggest that the direction of the right atrial pressure shifts induced by nitroglycerin does not depend on venous return, but is determined by the prevalence of flow changes in the superior vena cava or inferior vena cava.
Asunto(s)
Función del Atrio Derecho/efectos de los fármacos , Presión Sanguínea , Nitroglicerina/farmacología , Animales , Gatos , Contracción Miocárdica/efectos de los fármacos , Donantes de Óxido Nítrico/farmacología , Factores de Tiempo , Vena Cava Inferior/efectos de los fármacos , Vena Cava Superior/efectos de los fármacosRESUMEN
In anesthetized cats, nitroglycerin increased blood flow in the superior vena cava and decreased the flow in the inferior vena cava and total venous return. Simultaneous changes in right atrial pressure could be either positive or negative. The shifts in the superior vena cava flow and right atrial pressure preceded the corresponding alterations in the inferior vena cava flow and venous return.
Asunto(s)
Presión Sanguínea/efectos de los fármacos , Atrios Cardíacos/efectos de los fármacos , Nitroglicerina/farmacología , Vasodilatadores/farmacología , Venas Cavas/efectos de los fármacos , Animales , Gatos , Atrios Cardíacos/metabolismo , Hemodinámica , Flujo Sanguíneo Regional , Venas Cavas/metabolismoRESUMEN
Changes of the right atrial pressure and systemic haemodynamics following action of catecholamines (epinephrine and norepinephrine) were studied in acute experiments on anaesthetised mongrel cats with artificial lung ventilation and opened chest. Maximal changes of the right atrial pressure took place on the 12th-16th second following catecholamine administration. In that case, the atrial pressure could be decreased or increased. At the moment of maximal changes of the right atrial pressure, the venous return and the right ventricular myocardial contractility (the first derivative of the right atrial pressure, dP/dt max) increased more if the right atrial pressure decreased, as compared with the animals whose right atrial pressure augmented. The findings suggest that at the time of the maximal changes of the right atrial pressure following action of catecholamines, there may be a direct connection of the right atrial pressure with interrelation of venous return and the right ventricular contractility. The right atrial pressure, however, is a dependent parameter but it does not determine the venous return.
Asunto(s)
Función del Atrio Derecho/efectos de los fármacos , Presión Sanguínea/efectos de los fármacos , Epinefrina/farmacología , Norepinefrina/farmacología , Animales , Gasto Cardíaco/efectos de los fármacos , Gatos , Epinefrina/administración & dosificación , Inyecciones Intravenosas , Norepinefrina/administración & dosificación , Flujo Sanguíneo Regional/efectos de los fármacos , Vena Cava Inferior/fisiología , Vena Cava Superior/fisiología , Presión Venosa/efectos de los fármacosRESUMEN
In experiments on cats, dopamine induced constriction, while sodium nitroprusside dilation of arteries and veins perfused with a constant volume of autoblood in the decentralized gastrocnemius muscle and small intestine. Vascular responses to both test substances were reduced under the effect of hypothermia and especially under the effect of hypoxia alone. During combined exposure to hypoxia and hypothermia the decrease in the amplitude of vascular responses to dopamine and sodium nitroprusside was similar to that observed during hypoxia alone.
Asunto(s)
Dopamina/farmacología , Músculos/citología , Nitroprusiato/farmacología , Animales , Antihipertensivos/farmacología , Arterias/efectos de los fármacos , Arterias/metabolismo , Cardiotónicos/farmacología , Gatos , Femenino , Hipotermia , Hipoxia , Intestino Delgado/efectos de los fármacos , Masculino , Músculo Esquelético/citología , Músculo Esquelético/metabolismo , Músculos/metabolismo , Venas/efectos de los fármacos , Venas/metabolismoRESUMEN
The type and magnitude of changes in blood flow in the anterior (cranial) and posterior (caudal) caval veins and shifts in the mean right atrial pressure induced by catecholamines (epinephrine and norepinephrine) were studied in acute experiments on cats. It was found that irrespective of right atrial pressure shifts, the increase in the blood flow in the anterior vena cava was more pronounced than in the posterior vena cava and was determined by blood redistribution due to more pronounced increase in vascular resistance in the abdominal aorta basin.
Asunto(s)
Presión Sanguínea/efectos de los fármacos , Epinefrina/farmacología , Norepinefrina/farmacología , Venas Cavas/efectos de los fármacos , Venas Cavas/fisiología , Animales , Gatos , Relación Dosis-Respuesta a Droga , Epinefrina/administración & dosificación , Hemodinámica/efectos de los fármacos , Norepinefrina/administración & dosificación , Flujo Sanguíneo Regional/efectos de los fármacos , Resistencia Vascular/efectos de los fármacos , Vena Cava Inferior/efectos de los fármacos , Vena Cava Inferior/fisiología , Vena Cava Superior/efectos de los fármacos , Vena Cava Superior/fisiologíaRESUMEN
Changes in venous return compared with changes in negative intrathoracic pressure at deep breathing and in right atrial pressure after the administration of pressure stimuli on the cardiovascular system were studied in acute experiments with anesthetized cats. No correlation was found between the value of negative intrathoracic pressure and the mean value of venous return or between the mean value of right atrial pressure and the mean value of venous return in the intact cardiovascular system provided the animal body is placed horizontally. It was concluded that both the negative intrathoracic pressure and the right atrial pressure are not the main factors influencing the venous return volume.
Asunto(s)
Circulación Coronaria/fisiología , Corazón/fisiología , Animales , GatosRESUMEN
Dynamics of changes in right-atrial pressure and venous pressure measured in the inferior and superior vena cava at their orifices (central venous pressure) after bolus injection of 20 ml physiological saline or epinephrine (5.0 mg/kg) was studied in acute experiments on cats. The initial pressure in the right atrium was equal to that in caval veins. Pressor stimuli either increased or decreased the right atrial pressure, but always increased blood pressure in the caval veins. Moreover, right atrial pressure returned to the initial level more rapidly compared to that in caval veins. Our results suggest that the dynamics of the right-atrial pressure does not reflect the shifts in the central venous pressure.