Exchangeable electrolytes in heart disease.

The results of measurements of body sodium, chloride and potassium by isotope dilution or whole body counting in patients with heart disease are reviewed. In patients with cardiac oedema exchangeable sodium and chloride are increased while body potassium tends to be decreased or normal. The findings in normonatraemic hypochloraemia, hypokalaemia and metabolic alkalosis, in diuretic hyponatraemia and in dilutional hyponatraemia are reviewed and their possible consequences in terms of changes in electrolyte gradients are discussed. The limitations and usefulness of measurements of exchangeable electrolytes in heart disease are mentioned.