[Venous return in systemic haemodynamics].

The paper generalizes unclear problems of venous return to the heart under different conditions. Data are presented on the venous return/cardiac output ratio, general peripheral resistance, arterial pressure and vascular bed capacity. A concept of double wave nature of formation of the circulation pressor systemic responses is advanced.

Contribution of splanchnic and musculocutaneous vascular compartments to the formation of blood flow volume in the vena cava posterior during catecholamine treatment.

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.

[Haemodynamic structure of the venous return changes in action of pressor neurogenic and humoral stimuli upon the circulation system].

In cats, constancy of blood flow changes was found in the anterior vena cava under the effect of pressor neurogenic and humoral stimuli. The latter proved to be more efficient in their effect. In the pressor systemic responses, changes of the blood flow in the anterior vena cava yielded the greates contribution.

Changes in the resistance in brachiocephalic artery and thoracic aorta basins during depressor reactions of the circulatory system.

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.

Role of vascular system adrenoceptors in formation of venous return.

In experiments on cats electromagnetic flowmetry showed that contribution of the blood flow in the anterior and posterior cava venae to the formation of venous return during stimulation of adrenoceptors with catecholamines is determined by the dynamics of systemic pressor reactions. At the moment of maximum elevation of blood pressure, the major role is played by blood flow changes in the anterior vena cava, while the posterior vena cave plays the predominant role during the period of maximum venous return. Under the action of alpha- and beta-adrenoceptor blockers, venous return is predominantly formed by the blood flow in the posterior vena cava independently on the dynamics of systemic depressor reactions. Adrenoceptor blockade modulates the structure of venous return formation in response to catecholamines: alpha-adrenoceptor blockade reduced the role of anterior vena cava blood flow and increased that of posterior vena blood flow in the formation of venous return, while beta-adrenoceptor blockade induced opposite changes. It is concluded that alpha- and beta-adrenoceptors predominantly control changes in the blood flow in the anterior and posterior cava venae, respectively.

[Changes in the major circulation vessel capacity and their role in forming the venous return shifts under the effect of catecholamines].

The study relates to characteristics of the major circulation vessel capacity and their part in forming the venous return shifts under the effect of catecholamines. In anesthetized cats, using the developed technique of controlled experiment enabling to stabilize the blood flow in the circulation arterial segment, fulfilling of pressor responses to i. v. administration of noradrenaline, adrenaline was found to increase the venous return, on the average, by 40% by means of changes in the major circulation vessel capacity (its venous segment, mainly). About 5% of the blood volume seems to become mobilized in the animal organism.

[Participation of the cava vein blood flow in forming the total venous return under influence of different modality stimuli on the circulation system]. / Uchastie izmenenii krovotoka polykh ven v formirovanii velichiny summarnogo venoznogo vozvrata pri deistvii na sistemu krovoobrashcheniia stimulov razlichnoi modal'nosti.

Participation of the anterior and posterior veins cava in forming the total venous return under pressor and depressor effects, stimulation of depressing foci of the medulla's ventral part, enhancement of pulmonary ventilation, hypoxia, hypothermia, administration of acetylcholine, histamine, corinfar, was shown to depend on the blood flow shift direction in each of the veins cava, dynamics of shifts' development in time, and intensity of the stimulus. In systemic responses, the blood flow shifts in the vena cava anterior much contribute to the total venous return at the maximum of the systemic arterial pressure rise (r = 0.87) whereas contribution of the vena cava posterior is the greatest during a later occurring increase in the venous return (r = 0.84). Along with increase in the stimulus intensity the vena cava anterior's part in forming the venous return becomes more limited whereas that of the vena cava posterior is enhanced.

[Comparative characteristics of systemic and pulmonary hemodynamics during changes in the heart preloading]. / Sravnitel'naia kharakteristika gemodinamiki bol'shogo i malogo krugov krovoobrashcheniia pri izmeneniiakh prednagruzki serdtsa.

A greater degree of relative shifts in the systemic arterial pressure in enhancing the right heart pre-load as compared with its diminishing. A primary role of the compensation mechanisms of the enhanced systemic arterial pressure level. The main role in the compensation of integral shifts of the arterial pressure induced by changes in the heart pre-load was shown to belong to the vascular resistance both in the major and the minor circulation circles. An idea of a greater involvement of the capacity function of the vascular bed in the minor circulation circle as compared with that in the major circulation circle in systemic haemodynamic shifts in changes of the heart pre-load, has been advanced.

[Efficacy of neurogenic and humoral stimuli in venous return in cats]. / Effektivnost' deistviia neirogennykh i gumoral'nykh stimulov na venoznyi vozvrat u koshek.

Humoral stimuli (i.v. adrenaline) proved to exert a greater effect on venous return in anesthetized cats than neurogenic those (electrical stimulation of either brain stem or femoral nerve). The part of cardiac output, however, in arterial blood shifts was the same. The latter finding is, probably, due to a discrepancy between changes occurring in the venous return and cardiac output caused by blood detention within the lung circulation as well as by an elevation of the blood pressure.

[Hemodynamic mechanisms of blood flow regulation in the vena cava anterior]. / Gemodinamicheskie mekhanizmy reguliatsii krovotoka v perednei poloi vene u koshek.

A similarity of the blood flow shifts in response to every single pressor or depressor stimulus in the v. cava anterior in cats and a possibility of dissimilar changes of capacity of the vein's vascular basin under the effect of one and the same stimulus, are revealed. This dissimilarity is mainly due to a skin-muscular component of this vascular basin. An increase in the central venous pressure from 0 to 40 mm of water limits the extent of shifts in the capacity function of the v. cava anterior's basin. The blood flow changes in the v. cava anterior is mainly due to a relationship among regional components of the vessels' total peripheral resistance. A potential possible contribution of the v. cava anterior basin vessels capacitance's shifts constitutes 17.5%, whereas under the effect of neurogenic stimuli in the increase of the blood flow in the v. cava anterior may be completely (up to 100%) maintained by a drop of the capacitance of the vein's vascular basin.

[Changes in the venous vessels capacitance in the cat forepaw in response to neurohumoral stimuli]. / Izmeneniia emkostnoi funktsii venoznykh sosudov perednei lapki koshki v otvet na neirogumoral'nye stimuly.

The trend in changes of the cat forepaw vessels' capacity was found to practically not differ from the trend in shifts in the vena cava anterior basin's capacity: in both areas the capacity decreases in response to pressor neurogenic stimuli and decreases or increases under the effects of pressor and depressor humoral stimuli. The data obtained suggest that the trend in shifts of the vena cava anterior basin's capacity under the effects of pressor humoral stimuli mainly depends on the skin-muscular area's vessels, whereas the trend in shifts of the vena cava anterior basin's capacity under the effects of depressor humoral stimuli depends, apparently, on the shifts in the brain vessels' capacity function.

[Quantitative evaluation of participation of the cardiac and vascular components in arterial pressure changes]. / Kolichestvennaia otsenka uchastiia serdechnogo i sosudistogo komponentov v dinamike pressornykh sdvigov arterial'nogo davleniia.

Under the effect of adrenaline upon the circulation system, vascular components of the blood pressure (BP) was shown to provide 75% of the maximal rise of the BP and the cardiac component--25%, whereas in response to noradrenaline the values were 62% and 38%, resp., in cats. In further development of systemic responses the role of cardiac component is enhanced whereas the role of vascular component becomes limited. Participation of the vascular component alone in systemic shift induced with catecholamines, under conditions of stabilised cardiac output, decreases the duration of the BP rise, whereas a combined rise of peripheral resistance and cardiac output in natural circulation provides an elongation of the BP changes.

[Effect of different regimes of the artificial respiration on systemic hemodynamics]. / Struktura sistemnoi gemodinamiki pri razlichnykh rezhimakh iskusstvennoi ventiliatsii legkikh.

An increase in artificial lung ventilation induced a suppression in arterial and venous portions of the circulation, whereas a limited lung ventilation induced pressor shifts of these parameters. The findings suggest that the value of respiratory volume per a cycle rather than shifts in the minute respiratory volume, affects the values of circulation systemic parameters.