Hyponatremia in the Neurologic Patient in Intensive Care Unit: Etiology and Treatment

Hyponatremia is the most prevalent electrolytic disorder found in patients with neurologic disorder hospitalized in the intensive care unit (ICU). It is a poor prognostic factor and increases mortality rates in these patients. We present a review concerning the etiology, pathophysiology, and particularly, the treatment of this pathology. Most cases of hyponatremia are caused either by the syndrome of inappropriate antidiuretic hormone secretion or by the cerebral salt wasting syndrome. The difference between them is the volemia of the patient, which is difficult to assess, especially in the ICU. Adrenal insufficiency, hypovolemia, and inadequate fluid resuscitation are also common causes of hyponatremia in the neurologic ICU. Even if the therapeutic approach varies accordingly to the concomitant neurological disorder and how fast the hyponatremia occurred, hypertonic saline solution is the cornerstone of the treatment in severe or symptomatic hyponatremia. The use of other molecules, such as fludrocortisone and antidiuretic hormone antagonist could be an interesting option in the future. The pathophysiology of hyponatremia in neurologically ill patients is not well understood. However, HSS is the treatment of choice in severe or symptomatic hyponatremia in this population.