Hyponatremia and hypernatremia in the emergency department: severity and outcomes

Abstract

Objective: Hyponatremia and hypernatremia are common electrolyte disorders. Few studies to date have focused on patients presenting to the emergency department (ED) with sodium (Na) disorders. Our objective was to determine the incidence and outcomes of hyponatremia and hypernatremia in ED patients.

Methods: This study was a retrospective, single-center review of electronic medical records at an academic suburban ED with approximately 100,000 annual visits. Subjects included consecutive adult ED patients with Na levels measured while in the ED in 2019. Demographic, clinical, and laboratory data were recorded. Outcomes data, including hospital admission, intensive care unit (ICU) admission, mortality, and length of stay (LOS), were recorded. The primary outcome was inhospital death. Secondary outcomes were hospital admission, ICU admission, ED LOS, and hospital LOS. Univariable and multivariable linear and logistic regression analyses were performed to explore the association of candidate predictor variables and outcomes.

Results: Na was measured in 57,427 adults (54%) among a total of 106,764 assessed ED visits in 2019. The mean±standard deviation age was 54±21 years, and 47% of participants were male. Mild, moderate, and severe hyponatremia and hypernatremia occurred in 8%, 2%, and 0.1% of patients and 1%, 0.2%, and <0.1% of patients, respectively. Hospital and ICU admission and mortality rates increased as Na levels increased or decreased further from normal. Adjusted odds ratio (95% confidence interval) values for hospital mortality were 2.39 (1.97-2.90) for mild hyponatremia, 3.93 (2.95-5.24) for moderate hyponatremia, 6.98 (2.87-16.40) for severe hyponatremia, 3.65 (2.47-5.40) for mild hypernatremia, 8.58 (4.92-14.94) for moderate hypernatremia, and 55.75 (11.37-273.30) for severe hypernatremia. Hypernatremia was associated with a greater risk of death than hyponatremia. Patients with hyponatremia and hypernatremia had increased LOS times compared to those with normal Na levels.

Conclusion: Hyponatremia and hypernatremia were associated with greater rates of hospital admission, ICU admission, mortality, and prolonged hospital LOS times.

Keywords: Emergency department; Hypernatremia; Hyponatremia.

Fig. 1.

Severity of hyponatremia and patient outcomes. P<0.001 for all outcomes. ICU, intensive care unit.

Fig. 2.

Severity of hypernatremia and patient outcomes. P<0.001 for admissions, P=0.004 for intensive care unit (ICU) admissions, and P<0.001 for mortality.