[Sodium and diseases in the aged].

The authors describe serum sodium levels in elderly patients at hospitalization and evaluate the role attributable to drugs, diseases, nutrition and fluid balance. Among 167 patients (average age 75.29 +/- 7.14), 132 (79.04%) had normal sodium balance, 34 (20.36%) were hyponatremic and only 1 (0.60%) was hypernatremic. Patients who had serum sodium levels above 129 mEq/l were asymptomatic. In five cases hyponatremia was acute and severe (less than or equal to 127 mEq/l). Seven patients who had serum sodium levels less than 127 mEq/l presented psychiatric and neurological manifestations, which subsided completely after prompt correction of the electrolyte disorder. The authors suggest that the pathogenesis of hyponatremia in pathological states in the elderly is complex, although iatrogenic causes play a fundamental role.