The relation of renal blood flow to effective arterial pressure in the intact kidney of the dog.

Interest att’ached to renal blood flow during traumat#ic and hemorrhagic shock, and the significance of reduction in renal blood flow in the etiology of renal hypertension has made it desirable to know what effect changes in aortic pressure, vasomotor activity, and changes in effective viscosity of the blood have in causing observed allteratOions in renal vascular resistance and blood flow. Although apparently successful studies of this type have been made on the isolated hind limb of the dog (1, 2, 3), it was thought that the kidney’s susceptibility to adverse conditions encountered during in vitro perfusion with blood and other fluids would make it desirable to pursue such studies in tlhe intact animal. Thus, edema formation, settling or agglutination of erythrocytes, clotting, or the formation of toxic or constrictor substances which might occur in shed blood would be minimized or entirely eliminated. The present study was accomplished with minimal disturbance to the kidney by a special method of renal vein cannulation. The relationship of effective arterial pressure to total renal blood flow was then evaluated t)hrough variation of the aortic pressure by compression of the dorsal aorta just above the renal artery. In some animals the kidneys under observation were denervated. METHOD. Dogs anesthetized with 30 mgm. per kgm. of sodium pentobarbital administered intravenously were used in this study. Surgical procedures involved a retroperitoneal approach to tlhe dorsal aorta and the left kidney, cannulation of a femoral artery and vein, and c.annulation of both external jugular veins. The method of measuring renal venous outflow has been described in previous rep0rt.s (4,5). It consists in passing a jugular sound, perfused with saline, into the left renal vein via the vena cava. Aft,er heparinization of the animal with 4 mgm. per kgm. initial dose (5 mgm. total dose was given every half-hour t,hereafter), the cannula is securely ligated, and blood is permitted to pass through the .cannula, a,nd by a connecting tube is immediately passed into the opposite jugular vein. From this circuit, lo-20 cc. aliquot’s of blood are periodically shunted into graduated cylinders. By timing accurately the period of outflow, total renal blood flow (RBF) in cubic centimeters per minute can be calculated. In t,his report all flow values are expressed in terms of cubic centimeters per minute per gram of kidney mass (wet weight), facilitating the grouping of data in the figures and tables. Because the renal cannula circuit itself offered some resist’ance to blood flow,