Hyponatremia at Admission in Hospitalized Patients With COVID-19: Risk Factors and Impact on Prognosis

Background: Electrolyte disorders, particularly hyponatremia, have been reported in a considerable number of patients with Coronavirus Disease 2019 (COVID-19). Objective: The current study aims to evaluate the risk factors, symptoms, and prognosis of hyponatremia in hospitalized patients with COVID-19. Methods: In this retrospective cohort study, 467 patients with COVID-19 were divided into 4 groups based on the sodium level at the time of admission: normal, mild hyponatremia, moderate hyponatremia, and severe hyponatremia. Symptoms, laboratory findings, and prognosis were compared among these groups. The risk factors for the occurrence of moderate/severe hyponatremia and the association of hyponatremia with in-hospital mortality were investigated using logistic regression analysis. Findings: Hyponatremia was diagnosed in 60% of the patients. The prevalence of mild, moderate, and severe hyponatremia was 80.7%, 15.1%, and 4.2%, respectively. The severity of the clinical symptoms and level of hypoxia showed no significant difference between the groups. White blood cells count was significantly higher and lymphocyte percentage was significantly lower in hyponatremia groups compared to the normal group. The history of chronic kidney disease was an independent risk factor for the moderate/severe hyponatremia (Adjusted OR=5.11, 95%CI: 1.72-15.2, P=0.003). After adjustment of different risk factors, moderate/severe hyponatremia remained a significant independent risk factor for in-hospital mortality (OR=2.58, 95%CI: 1.13-5.88, P=0.024). Conclusion: Hyponatremia is prevalent in COVID-19 patients. However, it is not definitely associated with severity of COVID-19 at the time of admission. Moderate/severe hyponatremia is associated with higher in-hospital mortality rate despite the similarity of disease severity between the sodium groups.