Hyponatremia is associated with poor outcome in COVID-19

Our objective was to describe the impact of hyponatremia on the outcomes of COVID-19 patients [outcomes selected: intensive care unit (ICU) admission, mechanical ventilation or death].

Two groups of COVID-19 patients were retrospectively screened on the basis of plasma sodium level at admission: hyponatremic (sodium < 135 mM, n = 92) or normonatremic (sodium ≥ 135 mM, n = 198) patients. Pearson's chi-² (qualitative variables) and Student's T tests (quantitative variables) were used to compare the two groups. A multiple logistic regression model was used to explore the association between patients' clinical data and outcomes.

Hyponatremia was frequent but generally mild. There were more male patients in the hyponatremic group (p = 0.014). Pulmonary lesions on the first thoracic CT-scan performed during hospitalization were significantly more extensive in the hyponatremic group (p = 0.010). ICU admission, mechanical ventilation or death were significantly more frequent in hyponatremic compared to normonatremic patients (37 versus 14%; p < 0.001; 17 versus 6%; p = 0.003; 18 versus 9%, p = 0.042, respectively). Hyponatremia was an independent predictor of adverse outcomes (adjusted Odds-ratio: 2.77 [1.26-6.15, p = 0.011]).

Our study showed an independent relationship between hyponatremia at admission and transfer to ICU, use of mechanical ventilation or death in COVID-19 patients. Hyponatremia may reflect the severity of underlying pulmonary lesions. Our results support the use of sodium levels as a simple bedside screening tool for the early identification of SARS-CoV-2 infected patients at high risk of poor outcome.