Incidence of Hyponatremia Among Critically Ill Patients With and Without COVID-19 Infection at a Community Teaching Hospital.

Background: Various studies have demonstrated the incidence of hyponatremia in patients with Coronavirus Disease 2019 (COVID-19); however, to our knowledge, no study has assessed the difference in the incidence of hyponatremia in patients with and without COVID-19. Purpose: To compare the incidence of hyponatremia in patients requiring intensive care unit (ICU) admission with and without COVID-19 infection. Methods: This was a single-center, retrospective cohort study of patients with a diagnosis of pneumonia from February 2019 to January 2020, or a diagnosis of COVID-19 from June 2020 to May 2021. Included patients were matched on age and sex. The primary outcome was the incidence of hyponatremia within 72 h of admission. Secondary endpoints collected included severity of hyponatremia, symptomatic hyponatremia, and lowest serum sodium. Results: There were 99 and 104 patients included in pneumonia and COVID-19 arms, respectively. Twenty-nine patients in the pneumonia group and 56 patients in the COVID-19 group had a sodium level <134 mEq/L (29% vs 56%, RR 1.84, P < .01). The mean lowest serum sodium within 72 h of admission was 136.9 mEq/L in the pneumonia group and 134.5 mEq/L in the COVID-19 group (P < .01). Other notable findings included days of mechanical ventilation (3 days vs 8 days, respectively; P < .01), downgrade from the ICU (74.8% vs 59.6%, P = .02), ICU length of stay (4 days vs 10 days, P < .01), hospital length of stay (6 days vs 14 days, P < .01), and mortality (16.2% vs 39.4%, P < .01). Conclusion: Among critically ill patients with COVID-19, the risk of hyponatremia was significantly greater than the risk in critically ill patients with pneumonia.