THE VELOCITY OF DISTRIBUTION OF SUCROSE BETWEEN PLASMA AND INTERSTITIAL FLUID, WITH REFERENCE TO THE USE OF SUCROSE FOR THE MEASUREMENT OF EXTRACELLULAR FLUID IN MAN 1

Abstract

That sucrose is not metabolized in man (as it is in the dog) was confirmed. In 4 patients it was demonstrated by the 5 hour infusion-equilibration technic plus 24 hr. urine collection that sucrose has the same volume of distribution, within the limits of technical error, as does inulin. Because the difference in molecular wt. between sucrose and inulin may make a significant difference in the rate of equilibration within the interstitial fluid, sucrose was substituted for inulin in a study of the kinetics of mixing between plasma and interstitial fluid by means of a calibrated infusion technic in which a priming injn. was omitted. The results obtained on 4 normal subjects and 10 patients with a variety of pathological disturbances show that the mixing process is of such a nature that within 30 to 180 min. after the beginning of a sucrose infusion (without a priming dose), the plasma has for practical purposes come into equilibrium with the interstitial fluid. The volume of distribution of sucrose measured when apparent equilibrium distr. has been reached agrees in 3 patients with the vol. of distribution as measured by the 5 hr. infusion-total recovery method. This approach to equilibrium is attained despite the fact that the plasma concn. is still increasing, a circumstance that indicates relatively rapid mixing between plasma and interstitial fluid. The method has the advantage that it reveals failure to attain equilibration between the plasma and extracellular fluid in any particular patient.