Severe hypernatremia in the emergency department: a retrospective, single-center study

Hypernatremia is less common than hyponatremia in emergency department (ED) settings but has been associated with adverse clinical outcomes. While prior studies have primarily focused on critically ill or inpatient populations, data describing hypernatremia at the time of ED presentation remain limited. In particular, the clinical characteristics and early management patterns of patients with severe hypernatremia have not been well characterized in ED settings.

We conducted a retrospective cohort study of all adult patients who visited a single tertiary-care emergency department and underwent serum sodium measurement. Patients were categorized by serum sodium level at presentation. For patients with severe hypernatremia, additional clinical data, treatments, serial sodium measurements, and outcomes were collected. Survival analyses were performed using Kaplan-Meier methods and Cox proportional hazards models to evaluate the association between hypernatremia and mortality in the overall cohort.

Among 6,818 emergency department visits, 4,917 patients (72%) were hospitalized. Hypernatremia was observed in 4.7% of hospitalized patients. Compared with normonatremia, patients with hypernatremia were older, had significantly impaired renal function, and showed markedly higher in-hospital mortality (44% vs. 14%, p < 0.001). Kaplan-Meier analysis demonstrated significantly lower survival in the hypernatremia group (p < 0.001), and Cox proportional hazards analysis confirmed hypernatremia as an independent predictor of mortality after adjustment for age, sex, and renal function (hazard ratio 2.4, p < 0.001). Among patients with severe hypernatremia (n = 31), mortality remained high (42%), with most patients presenting with altered mental status and requiring ICU admission. Sodium correction within the first 24 h was modest in the majority.

Hypernatremia was relatively uncommon among hospitalized ED patients but was strongly associated with increased mortality. Severe hypernatremia represents a high-risk condition characterized by critical illness and limited early sodium correction. These findings highlight the need for improved recognition and management strategies for hypernatremia in the emergency department.