A Super-Aged Case with Marked Hyponatremia Reaching 98 mEq/L;Clinical Implications of Low Serum Sodium

A 79-year-old man, an in-patient at a long-term hospital suffers from Alzheimer dementia and thyroid hypofunction. Recently, he had also suffered from pneumonia followed by impaired consciousness and referred to our hospital for further examination. At the time of admission, the level of consciousness was JCS III-200 and other vital signs were normal. He had no edema on his limbs but had dry skin. According to chest CT, we detected pneumonia. Based on the laboratory data on admission, we detected low osmolality of 206 mOsm/kg of water and serum Na 98 mEq/L, beside urinary Na 54.1 mEq/L. We confirmed severe hyponatremia of hypersecretion type. Fluid replacement therapy was started mainly with Ringer’s solution which is similar to extracellular fluid. We diagnosed it as SIADH induced by adrenal crisis based on the significant lower serum Na value and low blood sugar. Consequently, the patient was administered Hydrocortisone and Fludrocortisone acetate. On the 14th day, serum Na level improved from 98 mEq/L to 140 mEq/L. After daily monitoring of serum Na and urinary Na, administration of fludrocortisone acetate was terminated. The patient was discharged on 25th day, since serum Na was stabilized with oral administration of hydrocortisone and oral salt supplement. This case report shows that adrenal crisis can be triggered by pneumonia. In cases of impaired consciousness, if hyponatremia and hypoglycemia are observed, we may have to suspect the possibility of adrenal crisis. Therefore, urinary biochemical examination is an important part of the laboratory tests.