Managing hyponatremia in neurosurgical patients

Hyponatremia is common in neurosurgical patients and is associated with significant morbidity and mortality. Despite significant research efforts to date, we still lack a complete understanding of the pathophysiological mechanisms underlying hyponatremia in this patient setting. The purpose of this narrative review is to provide an overview of our understanding of hyponatremia in neurosurgical patients, the management principles, and the challenges that arise for the physician managing such patients. Challenges to managing these patients include: the fact that the syndrome of inappropriate antidiuretic hormone (SIADH) and cerebral salt wasting (CSW) may actually represent parts of the same clinical spectrum; the difficulty in distinguishing between CSW, SIADH, and the hypovolemic hyponatremia resulting from a normal pressure natriuresis caused by the administration of large fluid volumes; and that hyponatremia can result from therapeutic agents used in these patients. Treatment of the hyponatremia depends on factors such as the underlying neurosurgical pathology, whether the hyponatremia is acute or chronic, and the fluid status of the patient. Hypertonic saline is a common treatment option. Other treatment options include vasopressin 2 receptor antagonists and steroids, but large prospective trials are required to suitably assess their efficacy and safety in the neurosurgical setting. Of all the challenges that hyponatremia in neurosurgical patients present, perhaps the most pressing is the need for a better understanding of the underlying pathophysiological mechanisms. Only once we begin to better understand this can more efficacious treatments be directed against hyponatremia in this important population.