Both high and low serum sodium levels are associated with adverse outcomes for hospitalized patients with COVID-19, new research suggests.
In the retrospective study of 488 patients hospitalized with COVID-19 at one of two London hospitals between February and May 2020, hypernatremia (defined as serum sodium level >145 mmol/L) at any time point during hospital stay was associated with a threefold increase in inpatient mortality.
Hyponatremia (serum sodium level <135 mmol/L) was associated with twice the likelihood of requiring advanced ventilatory support. In-hospital mortality was also increased among patients with hypovolemic hyponatremia.
“Serum sodium values could be used in clinical practice to identify patients with COVID-19 at high risk of poor outcomes who would benefit from more intensive monitoring and judicious rehydration,” Ploutarchos Tzoulis, MD, PhD, and colleagues wrote in their article, which was published online on Feb. 24, 2021, in the Journal of Clinical Endocrinology and Metabolism.
The findings will be presented at the upcoming news conference held by the Endocrine Society
Should sodium be included in a risk calculator for COVID-19?
Dr. Tzoulis, professor of endocrinology at the University College London Medical School, said in an interview that “sodium could be incorporated in risk calculators across other routine biomarkers, such as white cell count, lymphocytes, and CRP [C-reactive protein], in order to provide a tool for dynamic risk stratification throughout the clinical course of COVID-19 and assist clinical decision-making.”
Moreover, he said, “we should follow less conservative strategies in the rate and amount of fluid resuscitation in order to prevent hypernatremia, which is induced by negative fluid balance and can often be iatrogenic.”
Asked to comment, Steven Q. Simpson, MD, professor of medicine in the division of pulmonary, critical care, and sleep medicine at the University of Kansas, Kansas City, said that the article is missing key results that would assist in interpreting of the findings.
“Data regarding diuretic use and sparing of fluid administration are not in the paper. ... It is simply not possible to tell whether serum sodium is a ‘predictor’ ... or if it is a side effect of other issues or actions taken by physicians in patients who are progressing poorly.
“To say that sodium needs to be included in a risk calculator is to subtly suggest that there is some causal association with mortality, and that has quite clearly not been established,” stressed Dr. Simpson, who is president of the American College of Chest Physicians but was not speaking for the organization.
He added: “The data are interesting, but not actionable. It is common practice in critical care medicine to adjust water and salt intake to maintain serum sodium within the normal range, so the paper really doesn’t change any behavior.”
Dr. Tzoulis said in an interview that, despite not having electronic medical record data on diuretic use or fluid input and output, “our acute physicians and intensivists at both study sites have been adamant that they’ve not routinely used diuretics in COVID-19 patients. Diuretics have been sparingly used in our cohort, and also the frequency of pulmonary edema was reported as below 5%.”
Regarding volume of fluid intake, Dr. Tzoulis noted, “At our hospital sites, the strategy has been that of cautious fluid resuscitation. In fact, the amount of fluid given has been reported by our physicians and intensivists as ‘on purpose much more conservative than the usual one adopted in patients with community-acquired pneumonia at risk of respiratory failure.’ ”