Severe hypernatraemia in adults

Abstract

In a prospective study of abnormalities of plasma sodium concentration carried out over one year 20 patients were identified who had a concentration exceeding 154 mmol(mEq)/1. Of these, eight patients had diabetes mellitus, eight had primary intracranial disorder, and four had become dehydrated. Five of the eight diabetics presented with hyperosmolar, non-ketotic precoma, and in all eight hypernatraemia developed despite treatment with hypotonic (0.45%) saline. There was a good correlation (r = -0.93) between the rates of change of plasma sodium and blood glucose concentrations, and thus a rise in plasma sodium concentration appeared to be a consequence of the treatment. In the early phase of treatment urinary sodium loss was extremely low despite a brisk diuresis, the infused sodium then predisposing the patients to hypernatraemia. All of the eight patients with intracranial disorders showed evidence of abnormal production of the antidiuretic hormone, six having frank diabetes insipidus. Severe hypernatraemia in this group was associated with a high mortality, fluid balance being difficult to maintain. Two of the four patients who had become dehydrated had had a recent gastrointestinal haemorrhage. In these patients infusion of 0.9% saline contributed to the hypernatraemia since urinary sodium loss was low. Severe hypernatraemia in adults is uncommon, but in established cases plasma and urinary biochemical indices should be measured frequently. Monitoring of the central venous pressure is usually necessary, and patients are best managed in an intensive care unit.