A New Method of the Measurement of Venous Return and Its Application : REGULATION OF THE VENOUS RETURN AND ITS REGIONAL DISTRIBUTION, A STUDY WITH CHIEF EMPHASIS ON THE CAROTID SINUS REFLEX

Abstract

Chapter I. The method of the measurement of vanous return A new method was advanced to measure the rate of venous return by a dilution technique employing the electric conductivity method. The validity of this method, as applied to the venous system, was confirmed in carefully controlled model-experiments and animal experiments. This study revealed that the measurement of venous flow by dilution technique was valid, when the electrode was placed at least 4 cm downstream to the junction of any main tributary and the caval vein. The observed venous return and the relative contribution of individual tributaries (regional distribution) in dogs weighing about 10 kg were : total venous return 1.41l/min ; superior caval vein 36.7%, inferior caval vein 63.3%, hepatic vein 36%, renal veins 16.7%, lower limbs and pelvic viscera 10.6%, taking the total venous return as 100. The author discussed the advantage and disadvantage of this method in actual measurement of the venous flow.Chapter II. Regulation of the venous return and its regional distribution ; the role of the carotid sinus reflex As an approach to the problem of the nervous control of venous return, the author studied the effect of carotid sinus reflex on the venous return in dogs ; the maneuvres employed were : the occlusion of the common, and internal and external carotid artery, and the carotid sinus denervation ; the effect of such maneuvres on the venous return and relative venous flow from different tributaries (regional distribution) was studied. The venous blood flow was measured by a dilution technique employing the electric conductivity method, such as described in Chapter I. The common carotid artery occlusion caused the venous return to increase; the carotid sinus denervation changed the regional distribution of the venous return. It became clear that the carotid sinus reflex does not uniformly affect the entire blood vessels of the body, but causes the distribution of blood flow to change. These observations support the veiw that the purpose of the circulatory adjustment, including the re-distribution of blood flow to different parts of the body.Chapter III. The role of the carotid sinus reflex in the hemodynamic response (venous flow) to the circulatory crisis produced by acute bleeding or induced anoxaemia In Chapter II it was found that the carotid sinus reflex was capable of modifying venous return and its regional distribution. In this Chapter the author sought answer to the question, happens to the venous return in a circulatory crisis and what role does the carotid sinus reflex play under such circumstances? For this purpose the author performed two experiments; one, that of an acute bleeding and, other, that of induced anoxaemia (inhalation of low O2 gas). Following acute bleeding there was marked increase in the hepatic venous flow indicating the driving out of the splanchnic blood depot; such increase in the hepatic venous flow in response to an acute bleeding was not seen after the destruction of carotid sinus nerve activity. The induced anoxaemia caused the total venous return to increase; increase was relatively marked in the superior caval venous flow, with the result that the weight of the superior caval venous flow to the total venous return was increased. For such change in the venous return partly responsible is the carotid chemoreceptor mechanism. However, in the case of the organism's response to the induced anoxaemia the effect of carotid sinus denervation was relatively insignificant as compared with the effect of the same maneuvre on the organism's response to acute bleeding.