Diagnosis and Management of Sodium Disorders in the Neurosurgical Patient

Abstract

Sodium disorders are the most common electrolyte abnormality among hospitalized patients and even more common in the neurosurgical patient population. Timely diagnosis and careful correction of serum sodium is an essential skill for the neurosurgical hospitalist and may greatly mitigate the risk of significant harm to the patient. Water dysregulation is the primary feature of sodium abnormalities and may manifest as hyponatremia due to syndrome of inappropriate antidiuretic hormone (SIADH) secretion or hypernatremia due to central diabetes insipidus (DI). Therapy for the correction of serum sodium must take into consideration the etiology of dysregulation, unique risks associated with different neurologic pathologies, and the risk of osmotic fluid shift associated with fluctuations in serum sodium. Rapidly correcting sodium levels may lead to a variety of unintended sequelae, including osmotic demyelinating syndrome (ODS), cerebral edema, seizure, pulmonary edema, and death. Since neurosurgical patients are at elevated risk for severe morbidity due to osmotic fluid shift, it is crucial that neurosurgical hospitalists have a firm understanding of water and sodium pathophysiology, expertise in the diagnosis and treatment of sodium abnormalities, and nuanced appreciation for the risks and features unique to neurosurgical diseases. This chapter outlines the most common etiologies of sodium disorders in the neurosurgical patient population and offers recommendations for their diagnosis and treatment. Hyponatremia due to hypovolemia, cerebral salt wasting (CSW), SIADH, and adrenal insufficiency (AI) will be highlighted first, followed by hypernatremia due to free water deficit in the setting of central DI and inadequate oral fluid intake.