Extracellular volume, renal clearance and whole body permeability—surface area product in man, measured after single injection of polyfructosan

Abstract

In 22 patients non-compartmental analysis was applied to plasma disappearance curves obtained after a single injection of polyfructosan to measure volume of distribution (Vd), renal clearance (Cl) and the whole body permeability—surface area product (P_dS) of the indicator. It was found that introduction of the theoretical plasma concentration at time zero, calculated as the injected amount divided by the plasma water volume independently determined, to the curves was necessary to determine the initial slope of the curve and subsequently calculate the P_dS. This ‘initial phase’ approximation had negligible effect on the calculations of V_d and Cl. The approximation, however, allowed extension of the non-compartmental analysis to include calculation of the whole body P_dS. The whole body P_dS for polyfructosan was found to be 0.68 ml/l00g.min or 429 ml/min. Assuming a capillary surface area of the whole human body of 50 cm²g^-1, the average whole body diffusional permeability coefficient, P_d for polyfructosan was found to be: 0.23 × 10^-5 cm·sec^-1.

Key Words:

• indicator dilution
• non-compartmental analysis
• plasma disappearance curve fitting
• plasma volume