Otto H. Gauer

Evidence of the Atrial Location of Receptors Influencing Urine Flow

Receptors believed responsible for the diuresis of negative pressure breathing have been located by observing the effect on urine flow of a stepwise engorgement of the intrathoracic vascular bed. Distension of the pulmonary arterial tree (injection of plastic beads) and of the entire pulmonary circulation (snares on the pulmonary veins) were without effect. A diuresis was however elicited by expansion of a balloon in the left atrium. It is concluded that stretch receptors in the left atrium and terminal pulmonary veins are instrumental in a mechanism linking changes in the actively circulating blood volume with homeostatic responses of the kidney.

Changes in Central Venous Pressure after Moderate Hemorrhage and Transfusion in Man

Changes in central venous pressure were recorded continuously before, during and for 40 to 50 minutes after hemorrhage and transfusion in the amounts of 6.5 cc. per Kg. and 8.1 cc. per Kg. The pressures obtained 15 to 20 minutes after onset of blood volume changes were independent of the rate of hemorrhage or transfusion. In the average subject of 70 Kg., ΔP/ΔV for zero time was 0.7 cm. of water pressure change per 100 cc. volume change. Recovery from hemorrhage was imperceptible during the one hour observation period, but recovery from transfusion was slightly faster.

[Homeostasis of extraarterial blood circulation; volume regulation as an independent physiologic parameter].

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The Effect of Moderate Changes in Blood Volume on Left and Right Atrial Pressures

The blood volume of 15 dogs was progressively increased an estimated 30 per cent by repeated blood infusions and decreased 30 per cent by stepwise hemorrhage. The pressures in the venous system, both atria and the pulmonary artery, rose and fell in unison with these moderate changes in blood volume and the new levels remained stable for at least 10 to 20 minutes. Although the right ventricle anatomically separates the systemic venous bed from the pulmonary circulation, small hemorrhages and transfusions have so little effect on its activity that, from the point of view of pressure volume relationships, the systemic veins and the left atrium are parts of the same functional unit.