Background Dysnatremia is an independent predictor of mortality in patients with bacterial pneumonia. There is paucity of data about the incidence and prognostic impact of abnormal sodium concentration in patients with coronavirus disease 19 (COVID-19). Methods This retrospective longitudinal cohort study, including all adult patients who presented with COVID-19 to two hospitals in London over an 8-week period, evaluated the association of dysnatremia (serum sodium < 135 or > 145 mmol/L, hyponatremia and hypernatremia, respectively) at several timepoints with inpatient mortality, need for advanced ventilatory support and acute kidney injury (AKI). Results The study included 488 patients (median age 68 years). At presentation, 24.6% of patients were hyponatremic, mainly due to hypovolemia, and 5.3% hypernatremic. Hypernatremia two days after admission and exposure to hypernatremia at any timepoint during hospitalization were associated with a 2.34-fold (95% CI 1.08 – 5.05, p=0.0014) and 3.05-fold (95% CI 1.69 – 5.49, p<0.0001), respectively, increased risk of death compared to normonatremia. Hyponatremia at admission was linked with a 2.18-fold increase in the likelihood of needing ventilatory support (95% CI 1.34-3.45, p= 0.0011). Hyponatremia was not a risk factor for in-hospital mortality, except for the subgroup of hypovolemic hyponatremia. Sodium values were not associated with the risk for AKI and length of hospital stay. Conclusion Abnormal sodium levels during hospitalization are risk factors for poor prognosis, with hypernatremia and hyponatremia being associated with a greater risk of death and respiratory failure, respectively. Serum sodium values could be used for risk stratification in patients with COVID-19.

Background: Sodium abnormalities (dysnatremia) are frequently observed in patients with community-acquired pneumonia and are associated with excess mortality. Data on the prevalence of hyponatremia and hypernatremia (serum sodium [Na] < 135 and > 145 mmol/L respectively) in patients with coronavirus disease 19 (COVID-19) are currently lacking. Methods: The aim of this study was to evaluate the prevalence and etiology of hyponatremia and hypernatremia at several timepoints during hospitalization of COVID-19 patients. This retrospective, longitudinal, observational study included all COVID-19 positive adult patients admitted to two London hospitals over an 8-week period (February to May 2020). Results: Clinic records were reviewed in 488 patients, 277 males (56.8%) and 211 females (43.2%), with a median age of 68 years. Comorbidities were documented in 79.6%, with the commonest being hypertension (45.7%), diabetes mellitus (25%), and chronic kidney disease (16.4%). Prior to admission, 25 patients (5.1%) had pre-existing chronic hyponatremia. At hospital presentation, median [Na] concentration was 137 mmol/L. Dysnatremia was present in 146 patients (29.9%), including 26 (5.3%) with hypernatremia and 120 (24.6%) with hyponatremia, of whom [Na] was 130-134 mmol/L in 90 (18.4%) and < 130 mmol/L in 30 (6.2%). Only 19% of patients with < 130 mmol/L underwent adequate laboratory assessment of the etiology of hyponatremia. Of those, based on a urinary sodium cut-off of 30 mmol/L, hyponatremia was classified as hypovolemia in 75% and non-hypovolemic in 25%. For the remaining hyponatremic cases, using 5 mmol/L as the cut-off value for plasma urea, 55.7% were classified as probable hypovolemic and 44.3% non-hypovolemic hyponatremia. There was an upward trajectory of [Na] values during hospital stay with a median increase of 2 mmol/L in the first 48 hours following admission. On the fifth day of hospitalization, the prevalence was similar for hypernatremia and hyponatremia (13.8% and 14.1%, respectively). On the tenth day, hypernatremia was more common than hyponatremia (14.2% vs 10.2% respectively). Analysis of [Na] throughout the hospital stay defined four subgroups; 185 patients (37.9%) remained normonatremic throughout hospitalization; 180 (36.9%) had exposure to hyponatremia; 53 (10.9%) were exposed to hypernatremia; and 70 (14.3%) experienced both hypernatremia and hyponatremia. Conclusions: Hyponatremia, usually mild, was common at admission in Covid-19 positive patients, while hypovolemic hyponatremia appeared to be the predominant etiology. During hospital stay, abnormal sodium concentration was recorded in more than two thirds of Covid-19 positive patients. The association of dysnatremia with the outcomes in hospitalized COVID-19 patients warrants further exploration.

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