Sodium and potassium concentrations in erythrocytes of patients with congestive heart failure

To study the changes in electrolyte concentrations in cells of patients with congestive heart failure, we measured the sodium and potassium concentrations in erythrocytes obtained from 34 stabilized patients treated with only digoxin and not with diuretics in order to avoid the effects of miscellaneous drugs and acute water overload. Patients were divided into classes I-III according to the NYHA classification. The values of urea nitrogen, hematocrit, and plasma sodium and potassium were not different among these groups. Serum digoxin concentration had a tendency to increase from class I to III, although not significantly. However, sodium concentration was significantly lower and potassium concentration was significantly higher in erythrocytes of class III, compared to class I patients. The erythrocyte sodium concentration was inversely related to the erythrocyte potassium concentration, but it was not related to the plasma sodium concentration or to the serum digoxin concentration. These results suggest that the reduced sodium concentration in patients with congestive heart failure was manifested earlier in erythrocytes than in plasma during long-term treatment with digoxin.