Venous Return as Affected by Cardiac Output and Total Peripheral Resistance

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Abstract
In anesthetized, open-chest dogs, flow from the superior and inferior venae cavae was diverted into a glass U-tube reservoir kept at body temp. Blood was returned to the right auricle by a constant perfusion pump (Vanton pump). By recording the height of the fluid in the reservoir a continuous record of the volume of blood displaced out of the animal into the reservoir or pooled in the animal was obtained. From this record, venous return at any instant in time was also obtained. In addition arterial pressure and venous pressures from various sites were detd. Analysis of data of 100 expts. reveals that a change in total peripheral resistance is accompanied by a change in venous return in the same direction. When the total peripheral resistance is increased there is a transient increase in venous return and a displacement of blood out of the animal into the reservoir. A decrease in resistance is associated with a decrease in venous return and pooling of blood in the animal. Evidence suggests that this is due to active changes in the tone of the post-arteriolar blood vessels, most likely in the veins, and supports the hypothesis of coordinated arteriomotor and venomotor activity.