Abnormal Sodium is a Predictor for Respiratory Failure and Mortality in Hospitalized Patients With COVID-19

Background: Hypernatremia and hyponatremia (serum sodium > 145 mmol/L and < 135 mmol/L, respectively) are independent risk factors for excess mortality in patients with bacterial pneumonia. We sought, for the first time, an association of sodium [Na] abnormalities with mortality, need for advanced respiratory support and Acute Kidney Injury (AKI) in hospitalized patients with coronavirus disease 19 (COVID-19). Methods: This retrospective, longitudinal, cohort study included 488 adults, 277 males and 211 females, with a median age of 68 years, who were hospitalized with COVID-19 to two hospitals in London over an 8-week period (February to May 2020). Results: The in-hospital mortality rate was 31.1% with a medial length of stay of 8 days. High [Na] levels at any timepoint during hospital stay were associated with significantly increased mortality rate (56.6% vs 21.1% in patients who remained constantly normonatremic; odds ratio 3.05, 95% CI 1.69-5.49; p<0.0001). On day 3 and on day 6, high [Na] values predicted mortality with an estimated odds ratio of 2.34 (95% CI 1.08 – 5.05, p=0.0014) and 2.40 (95% CI 1.18 - 4.85, p=0.001), respectively. Non-survivors had a significantly higher 5-day rise in serum [Na] when compared to survivors (3.60 mmol/L vs 1.14 mmol/L respectively, p<0.05). Patients with low serum [Na] levels on admission had a 2.18-fold increase (95% CI 1.34-3.46, p=0.001) in the likelihood of needing advanced ventilatory support compared to those with normal [Na] (31.7% vs 17.5%, respectively). However, exposure to hyponatremia at any timepoint, including at presentation or on day 3 or day 5, was not associated with excess risk of

death. AKI affected 37.1% of patients (21.3%, 7.4% and 8.4% stages 1, 2 and 3 respectively) but was not related to serum sodium values. Conclusions: In hospitalized COVD-19 patients, hypernatremia at any timepoint was associated with excess mortality, suggesting that [Na] concentration may facilitate risk stratification. In addition, whilst our data cannot prove causality, these findings highlight the significance of judicious rehydration in such patients.

Longitudinal Study of Prevalence of Sodium Abnormalities in Hospitalized 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.