STUDIES ON GANGRENE FOLLOWING COLD INJURY. IV. THE USE OF FLUORESCEIN AS AN INDICATOR OF LOCAL BLOOD FLOW: DISTRIBUTION OF FLUORESCEIN IN BODY FLUIDS AFTER INTRAVENOUS INJECTION 1

Abstract

The distribution of injected fluorescein, a fluorescent dye, was studied in normal rabbits. The measured intensity of fluorescence of the animals'' skin under u.-v. light indicated that fluorescence was maximal at a time when measurements of the amt. of dye in the blood showed the conc. to be falling rapidly. When Ringer''s soln. was injected into the peritoneal cavity and fluorescein was injected intraven., the exchanges of dye between the blood and the peritoneal fluid showed that the conc. of fluorescein in the peritoneal fluid increased during the time that fluid was being absorbed into the blood stream. In circumstances where the vol. of extravascular fluid may be changing, the movement of dye is not independent of the movement of water; the conc. of dye is the resultant of diffusion from the blood to the peritoneal fluid and filtration of peritoneal fluid plus dye back into the blood. The vol. of distribution of intraven. injected fluorescein in rabbits with ligated renal pedicles was 8.4[long dash]11.4% of the body wt. Sufficient amts. of dye were found in the bile and in the lumen of the gut to approximate the amt. which had disappeared from the extracellular phase. When fluorescein was added to whole blood and the mixture incubated at 37[degree]C, about 83% of the added dye could be recovered from the separated plasma. Osmotic manipulation of red cell size without changing surface area did not change the proportion of dye recovered from the fluid phase. The loss of dye was tentatively attributed to surface adsorption rather than cell penetration.