Hyponatremia is a frequent
electrolyte imbalance in hospital inpatients. Acute onset
hyponatremia is particularly common in patients who have undergone any type of brain insult, including
traumatic brain injury,
subarachnoid hemorrhage and
brain tumors, and is a frequent complication of intracranial procedures. Acute
hyponatremia is more clinically dangerous than chronic
hyponatremia, as it creates an osmotic gradient between the brain and the plasma, which promotes the movement of water from the plasma into brain cells, causing
cerebral edema and neurological compromise. Unless acute
hyponatremia is corrected promptly and effectively,
cerebral edema may manifest through impaired consciousness level,
seizures,
elevated intracranial pressure, and, potentially, death due to cerebral herniation. The pathophysiology of
hyponatremia in neurotrauma is multifactorial, but most cases appear to be due to the syndrome of inappropriate
antidiuretic hormone secretion (
SIADH). Classical treatment of
SIADH with fluid restriction is frequently ineffective, and in some circumstances, such as following
subarachnoid hemorrhage, contraindicated. However, the recently developed
vasopressin receptor antagonist class of drugs provides a very useful tool in the management of neurosurgical
SIADH. In this review, we summarize the existing literature on the clinical features, causes, and management of
hyponatremia in the neurosurgical patient.