Diagnosis and treatment of hypernatremia

Hypernatremia, defined as a plasma sodium concentration greater than 145 mmol/l, represents a deficit of water relative to sodium and is most commonly due to free water loss and/or inadequate free water intake, rather than sodium excess. The reported prevalence of hypernatremia varies depending on the clinical setting with retrospective analyses identifying a prevalence of 0.5-1 % in the community but up to 10 % in intensive care units. Patients with reduced cognition or consciousness have impaired access to free water making them particularly vulnerable to hypernatremia. Hypernatremia is associated with poorer outcomes including longer length of hospital stay, in-hospital mortality, and odds of discharge to hospice or nursing home. This review will describe the diagnosis and management of hypernatremia providing insight into physiological mechanisms underpinning salt and water homeostasis with particular focus on arginine vasopressin deficiency as an endocrine cause of hypernatremia.