THE EQUILIBRATION OF RADIOSODIUM (Na24), RADIOPOTASSIUM (K42), AND DEUTERIUM OXIDE (D2O) IN HYDROPIC HUMAN SUBJECTS 1

Abstract

Isotope dilution methods have been described for the determination of total exchangeable sodium (Nae) (1, 2), total exchangeable potassium (Ke) (3-5), and total body water (T.B.W.) (6-8) with Na24, K42 and D20 as tracers. The time required for equilibrium of distribution of each of the isotopes must be determined experimentally, since uniform mixing is an ex- plicit assumption with these methods (9). In normal human subjects the times required for 95 to 100 per cent equilibration were found to be 12 to 20 hours for Na24, 18 to 40 hours for K42, and 2 to 3 hours for D20 (1-7). The presence of ab- normal fluid collections, however, may produce significant delays in diffusion equilibrium.