THE VARIABILITY OF EXTRACELLULAR FLUID SPACE (SUCROSE) IN MAN DURING A 24 HOUR PERIOD WITH AN APPENDIX AN EXAMINATION OF A SEQUENCE OF RANDOMIZED ERRORS BY THE MONTE CARLO METHOD*†

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Abstract
A calibrated sucrose infusion technique with extracellular fluid volume (EFV) calculated by the difference method was described and evaluated in 17 studies of 10-24 hours'' duration. Indirect evidence was provided that parenterally administered sucrose is metabolized in man. An empirically satisfactory correction for the rate of sucrose metabolism was applied to the calculation of EFV by the difference method and compared with EFV calculated by the post-infusion recovery method. Sucrose space was calculated at hourly intervals, giving a mean sucrose space for the entire group of 19.4% body weight or 15.1 1 for the average individuals in this study. The average of the ranges of variation from the 3d hour (when equilibration had probably been achieved) until the end of the infusion was 29.3% (4.4 1) of the mean sucrose space. The average of the coefficient of variation over the same period was 8.4% (1.3 1). These shifts in sucrose space in control subjects were not predictable as to direction, magnitude or duration. The wide variability observed was not due to errors or to artifacts of the technique as shown in the examination for random compounding of analytic errors by the Monte Carlo method. It was considered reasonable that these measurements describe real fluctuations in EFV. A 6-hr sucrose infusion usually describes the mean EFV of an individual, but probably does not describe the normal variability of EFV. This variability of EFV demonstrates the complexity of the equilibration problem for any test molecule used in similar techniques and the difficulty in comparing EFV measured by different techniques. There is need for the development of a better technique to verify and measure precisely the changes in EFV as reported here.