The Rate of Attainment of Diffusion Equilibrium for Thiocyanate between Plasma and Transudates following the Intravenous Injection of Sodium Thiocyanate in Patients with Edema.

Estimations of the volume of extracellular fluid in man have been made by calculating the volume of body fluid through which thiocyanate is distributed after the intravenous administration of sodium thiocyanate (1, 2, 3). In the method as proposed, a known amount of sodium thiocyanate in solution is administered intravenously and blood is drawn for the measurement of the concentration of thiocyanate in the serum 1 or 2 hours after the injection (1, 2). It has been demonstrated in normal man that the distribution of thiocyanate is rapid and that diffusion equilibrium is attained within 1 hour after injection (1, 2, 3). The time required for the attainment of equilibrium for CNS after intravenous injection of NaCNS in patients with edema has not been established; the present report affords information on this problem. Measurement of the CNS concentrations of serum and edema fluid has been made on samples drawn simultaneously at various times after intravenous injection of NaCNS. To establish the time required for attainment of equilibrium by analyses of transudate and serum it was necessary to know what the concentration of CNS in a transudate should be, in relation to the concentration in the serum, in a given system at equilibrium. Lavietes, Bourdillon, and Klinghoffer (2) observed in a few experiments in edematous patients that the concentration of CNS in the serum was from 5 to 21 per cent higher than in the transudate at equilibrium, when samples were drawn 12 to 64 hours after the administration of CNS. These authors suggest that CNS may combine in some manner with protein. Studies of the protein concentrations of serum and transudate have been made in each instance in the present study, and the difference in CNS concentration between serum and transudate in each case has been analyzed in respect to the difference in protein concentration.