SERIAL MEASUREMENT OF TOTAL-BODY POTASSIUM IN CHRONIC RENAL-DISEASE

Measurement of the natural radioisotope 40K by whole body counting techniques is a useful and accurate assessment of lean body mass. Total body potassium (TBK) was measured with a whole body counter in 44 dialysed (group I), 12 nondialysed (group II) patients with chronic renal failure, and 5 patients (group III) with noazotemic renal disease. Serial measurements were performed at 2 to 6 month intervals for as long as 50 months. Predicted normal TBK (K(p)) was estimated from height, weight, age, and sex of each patient as determined from measurements in normals. Group I could be divided into three subgroups. In 25 patients (group IA), predialysis TBK/K(p) averaged 97% of normal and Δ TBK did not change significantly (+ 20 mEq). In 11 dialysis patients (group IB) TBK/K(p) was lower than normal and averaged 92.5±5.0% in four females and 85.2 ± 2.4% in seven males. Hemodialysis for 6 to 36 months in group IB females and males patients (group IC), predialysis TBK/K(p) averaged 98.7±3.5% but Δ TBK decreased 467 ± 99 mEq (-14.4%) over 6 to 36 months of dialysis. No significant change in TBK was noted in group II and III patients. These results indicate that TBK stores are maintained within normal limits in the majority of patients with chronic renal failure. Dialysis may increase TBK if K depletion had occurred before dialysis. On the other hand, dialysis may decrease TBK in a small group of patients who have normal TBK values before the onset of dialysis therapy. The mechanism responsible for the latter observation is obscure.