2023 Aug 24. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–.
Sodium is a dominant cation in extracellular fluid and is necessary for the maintenance of intravascular volume. The human body maintains sodium and water homeostasis by concentrating the urine secondary to the action of antidiuretic hormone (ADH) and increased fluid intake by a powerful thirst response. These mechanisms to protect against developing hypernatremia are impaired in certain vulnerable populations, vasopressin deficiency, or unresponsiveness at the renal tubular level. Hypernatremia is defined as a serum sodium concentration of greater than 145 meq/L.