Abnormal Sodium Levels Predict Risk of Mortality, Need for Ventilatory Support in COVID-19 Patients

Ploutarchos Tzoulis, MD, PhD

New research from an international team based in London indicates measurements of sodium levels in the blood of patients hospitalized with COVID-19 could help clinicians identify patients at a greater risk of death or respiratory failure.

The analysis, which included data from nearly 500 patients hospitalized with COVID-19 at a pair of London-based hospitals, indicates patients who developed high sodium levels during their hospital stay were 3 times more likely to die than those who maintained normal sodium levels.

"This study shows for the first time that patients presenting at the hospital with COVID-19 and low sodium are twice as likely to need intubation or other means of advanced breathing support as those with normal sodium," said lead investigator Ploutarchos Tzoulis, MD, PhD, MSc, Honorary Associate Professor in Endocrinology at University College London (UCL) Medical School in London, in a statement.

In the past, research has established a link between dysnatremia and risk of mortality among patients with bacterial pneumonia. With this in mind, investigators sought to determine whether measurements of sodium concentration in patients with COVID-19 provided any prognostic value. To do so, they designed their analysis as a retrospective longitudinal cohort study of patients presenting with COVID-19 to a pair of hospitals in London from February-May 2020.

All patients identified for inclusion in the analysis were aged 16 years or older and had a positive RT-PCRT test for SARS-CoV-2 on nasopharyngeal swab or other specimen. During their hospitalization, participants underwent measurements of serum sodium, urea, creatinine, and CRP on the day of presentation, day 3, day 6, day 11, day 18, the day of admission to the ICU, and within the 48 hours prior to discharge or death.

Primary outcome measurements for the study included inpatient mortality, need for advanced respiratory support, and acute kidney injury. For the purpose of analysis, hyponatremia was defined as a serum sodium level less than 135 mmol/L and hypernatremia as a serum sodium level greater than 145 mmol/L.

In total, 488 patients were identified for inclusion in the study. This cohort had a median age of 68 years. At presentation, 24.6% of patients were hyponatremic and 5.3% had hypernatremia. Investigators noted most cases of hyponatremia were due to hypovolemia.

In their analyses, hypernatremia two days after admission and exposure to hypernatremia at any point during hospitalization was associated with a 2.34-fold (95% CI, 1.08-5.05; P=.0014) and a 3.05-fold (95% CI, 1.69-5.49; P <.0001), respectively, increased risk of death compared to their normonatremic counterparts. Further analysis suggested hyponatremia at admission was associated with a 2.18-fold (95% CI, 1.34-3.45; P=.0011) increase in risk of needing ventilatory support.

Investigators also pointed out hyponatremia was not a risk factor for in-hospital mortality, except among a subgroup of patients with hypovolemic hyponatremia. Additionally, sodium levels were not associated with risk for acute kidney injury or length of hospitalization.

"Sodium measurements can inform doctors about which COVID-19 patients are at high risk of deterioration and death," Tzoulis added. "Sodium levels can guide decision making about whether a COVID-19 patient needs hospital admission or monitoring in the intensive care unit."

This study, “Dysnatremia is a predictor for morbidity and mortality in hospitalized patients with COVID-19,” was published in the Journal of Clinical Endocrinology & Metabolism.