Renal Blood Flow in Dogs Studied by Means of a Dye-Dilution Technique

Abstract

The renal blood flow in dogs was studied with a dye-dilution technique using indocyanine green. A new method of analyzing the dye-dilution curves was devised by which it was possible to estimate the magnitude of separate flow components of the curves. It could be shown that the curves comprise three different components, representing: (1) a rapidly circulating fraction containing most of the dye injected, (2) a more slowly circulating fraction, and (3) dye in recirculating blood. The influence of recirculating dye was studied. This fraction could be eliminated in the calculations of the blood flow values. To determinate the accuracy of the method, measurement of the renal venous outflow was made simultaneously. The blood pressure decreased during the outflow measurements. Though these always were made in the so-called “zone of autoregulation” it could be shown that renal blood flow diminished in parallel with the fall in blood pressure. Therefore, a modification of the outflow method was devised by which it was possible to obtain the correct value for the renal blood flow at every moment during the hemorrhage. There was very good correlation between the dye-dilution values and the venous outflow measurements, giving a ratio of 1.003 with a correlation coefficient, r = 0.95. The rapid component of the curves represented 88 ± 3% of the total blood flow, the slow component of the curves 12 ± 3%. These components apparently indicate kidney compartments with different intensities of blood flow, presumably the major part of the cortex, and the medulla, respectively.