Total body sodium and chloride were measured by neutron activation analysis, and total body potassium was measured by whole body counting in ten male patients with endstage renal disease requiring chronic maintenance hemodialysis. The extracellular fluid volume was estimated from the simultaneously measured volume of distribution of bromine 77 and sodium 24. Total body water was estimated from the volume of distribution of triated water. Total body sodium and chloride were significantly increased above normal measured values, but total body potassium was not significantly different from normal. The increase in total body sodium could be attributed to an increase in exchangeable sodium because no significant change in the nonexchangeable portion of total body sodium could be detected. Extracellular fluid volume, estimated fro three different techniques (total body chloride, sodium 24, and bromine 77), and total body water were increased significantly above normal values. Extracellular fluid volume was correlated with exchangeable sodium, and total body water was closely correlated with total cation content (exchangeable sodium and total body potassium). The calculated intracellular fluid volume was decreased and was closely correlated with total body potassium. Despite adequate control of uremia by chronic maintenance hemodijalysis, body electrolyte composition and the distribution of body water remain significantly different from normal.

Total body protein (nitrogen), body cell mass (potassium), fat, and water were measured in 15 renal patients on maintenance hemodialysis (MHD). Total body nitrogen was measured by means of prompt gamma neutron activation analysis; total body water was determined with tritium labeled water; total body potassium was measured by whole body counting. The extracellular water was determined by a technique utilizing the measurement of total body chloride and plasma chloride. When compared with corresponding values of a control group of the same age, sex, and height, the protein content, body cell mass, and total body fat of the MHD patients were within the normal range. The only significant change was an increase in the extracellular water/body cell mass ratio in the male MHD patients compared to the controls. The lack of significant difference of the nitrogen values of the MHD patients compared to matched controls suggests that dialysis minimizes any residual effects of uremic toxicity or protein-calorie malnutrition. These findings further suggest that there is a need to reevaluate the traditional anthropometric and biochemical standards of nutritional status for MHD patients. It was concluded that it is particularly important to measure protein stores of MHD patients with low protein intake to ascertain nutritional status. Finally, in vivo measurement of total body nitrogen and potassium for determination of body composition provides a simple, direct, and accurate assessment of the nutritional status of MHD patients.

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