Site of Action of Hypertonic Saline in the Pulmonary Circulation

The effect of intravenous injections of 20 per cent saline on the pulmonary circulation was examined in 19 dogs. A marked rise of pulmonary arterial pressure was recorded in all cases. The pressure changes in the pulmonary veins depended largely on the choice of the vein for pressure measurements. A hypertensive response was usually recorded in the superior vein, while in the inferior vein no change or a slight fall in pressure was the rule. Left atrial pressure either did not change or fell. A difference in the anatomical structure of the muscle sphincter around the superior and inferior pulmonary veins is described. A potent sphincter surrounds the superior veins and infiltrates within their walls some-times as far as the border of the lung. The sphincter around the inferior veins is rudimentary and inconspicuous. Evidence is brought that hypertonic saline acts both on the pulmonary veins close to the left atrium and at the pulmonary arteriolar level.