Body composition and serum electrolyte concentrations

¹ Medical Service and Research Laboratory, Veterans Administration Hospital, and Departments of Medicine of Boston University and Tufts University Schools of Medicine, Boston, Massachusetts

Total exchangeable potassium, total exchangeable sodium, and total body water were simultaneously measured by dilution of K⁴², Na²⁴, and H³, respectively. Total exchangeable chloride was estimated at the same time by dilution of Br⁸². The concentrations of water, sodium, potassium, and chloride were measured in the serum. The subjects included three healthy young men. The remaining 65 subjects were patients, with illness associated with disorders of nutrition and of water and electrolyte metabolism ranging from cachexia to extreme obesity and from dehydration to massive anasarca. The results show that in this highly varied group of subjects, neither Na_e, K_e, nor Cl_e was correlated at all well with total body water when considered singly. Cl_e, in fact, was not considered to add useful information in the absence of information regarding other anions. However, the sum of Na_e and K_e correlated exceedingly well with total body water (r = .991). Additional relationships containing serum cation concentrations had even higher degrees of correlation. Furthermore, it was found that expressions capable of predicting Na_e or K_e could be derived from the data. Similarly high degrees of correlation were found when these regressions were computed for data from the literature.

Note:
With the Technical Assistance of E. Rossmeisl, R. McLean, H. Alpert, M. Halpin, and R. Gardner

Submitted on January 24, 1963