Impact of Hyponatremia on COVID-19-Related Outcomes: A Retrospective Analysis

Background: Sodium disturbances are observed in one-third of patients with COVID-19 and result from multifaceted mechanisms. Notably, hyponatremia is associated with disease progression and mortality. Aim: We aimed to analyze the impact of hyponatremia on COVID-19 outcomes and its correlation with clinical and laboratory parameters during the first wave. Methods: We evaluated the sodium levels of 558 patients with COVID-19 between 21 March 2020, and 31 July 2020, at a single center. We performed linear regression analyses to explore the correlation of sodium levels with COVID-19-related outcomes, demographic data, signs and symptoms, and laboratory parameters. Next, we conducted Pearson correlation analyses. A p-value < 0.05 was considered significant. Results: Hyponatremia was found in 35.3% of hospitalized patients with COVID-19. This was associated with the need for intensive care transfer (B = −1.210, p = 0.009) and invasive mechanical ventilation (B = −1.063, p = 0.032). Hyponatremia was frequently found in oncologic patients (p = 0.002) and solid organ transplant recipients (p < 0.001). Sodium was positively associated with diastolic blood pressure (p = 0.041) and productive cough (p = 0.022) and negatively associated with dry cough (p = 0.032), anorexia (p = 0.004), and nausea/vomiting (p = 0.007). Regarding the correlation of sodium levels with other laboratory parameters, we observed a positive correlation with hematocrit (p = 0.011), lymphocytes (p = 0.010), pCO2 (p < 0.0001), bicarbonate (p = 0.0001), and base excess (p = 0.008) and a negative correlation with the neutrophil-to-lymphocyte ratio (p = 0.009), the platelet-to-lymphocyte ratio (p = 0.033), and arterial blood glucose (p = 0.016). Conclusions: Hyponatremia is a risk factor for adverse outcomes in COVID-19 patients. It is associated with demographic data and clinical and laboratory parameters. Therefore, hyponatremia is an important tool for risk stratification in COVID-19 patients.