Prevalence and outcome of dysnatremia in patients with COVID-19 compared to controls

Abstract

Objective: The pandemic of coronavirus disease (COVID-19) has rapidly spread globally and infected millions of people. The prevalence and prognostic impact of dysnatremia in COVID-19 is inconclusive. Therefore, we investigated the prevalence and outcome of dysnatremia in COVID-19.

Design: The prospective, observational, cohort study included consecutive patients with clinical suspicion of COVID-19 triaged to a Swiss Emergency Department between March and July 2020.

Methods: Collected data included clinical, laboratory and disease severity scoring parameters on admission. COVID-19 cases were identified based on a positive nasopharyngeal swab test for SARS-CoV-2, patients with a negative swab test served as controls. The primary analysis was to assess the prognostic impact of dysnatremia on 30-day mortality using a cox proportional hazard model.

Results: 172 (17%) cases with COVID-19 and 849 (83%) controls were included. Patients with COVID-19 showed a higher prevalence of hyponatremia compared to controls (28.1% vs 17.5%, P < 0.001); while comparable for hypernatremia (2.9% vs 2.1%, P = 0.34). In COVID-19 but not in controls, hyponatremia was associated with a higher 30-day mortality (HR: 1.4, 95% CI: 1.10-16.62, P = 0.05). In both groups, hypernatremia on admission was associated with higher 30-day mortality (COVID-19 - HR: 11.5, 95% CI: 5.00-26.43, P < 0.001; controls - HR: 5.3, 95% CI: 1.60-17.64, P = 0.006). In both groups, hyponatremia and hypernatremia were significantly associated with adverse outcome, for example, intensive care unit admission, longer hospitalization and mechanical ventilation.

Conclusion: Our results underline the importance of dysnatremia as predictive marker in COVID-19. Treating physicians should be aware of appropriate treatment measures to be taken for patients with COVID-19 and dysnatremia.

Figure 1

Study flowchart. Flowchart showing patient enrollment. In total, 1041 patients were included in the study. Altogether 1021 patients were analyzed; 20 patients were excluded for absence of sodium levels measured on admission.

Figure 2

Prevalence of dysnatremia on admission in COVID-19 and controls. Sodium levels on admission in patients with COVID-19 (n = 172) and controls (n = 849) in each subgroup (hyponatremia, normonatremia, and hypernatremia). Data are presented as numbers (n) and percentage of patients.

Figure 3

(A) Time to death graph of all patients. Kaplan-Meier curves displaying probability to death within the first 30 days after admission for all patients in each subgroup (hyponatremia, normonatremia, and hypernatremia) (n = 1015). Patients with hypernatremia (red) have had an increased risk of death compared to normonatremic patients with a hazard ratio of 2.1. (B) Time to death graph in COVID-19. Kaplan–Meier curves displaying probability to death within the first 30 days after admission in COVID-19 in each subgroup (hyponatremia, normonatremia, and hypernatremia) (n = 171). Patients with dysnatremia have had an increased risk of death compared to normonatremic patients, with a hazard ratio of 11.5 for hypernatremia (red) and with a hazard ratio of 1.4 for hyponatremia (blue). (C) Time to death graph in controls. Kaplan–Meier curves displaying probability to death within the first 30 days after admission in controls in each subgroup (hyponatremia, normonatremia, and hypernatremia) (n = 844). Patients with hypernatremia (red) have had an increased risk of death compared to normonatremic patients with a hazard ratio of 5.3.