Hyponatremia has been reported between 20% and 35% of patients hospitalized for Covid-19, 1-5 with low serum sodium levels on admission often associated with progression to severe illness, mechanical ventilation, increased length of stay and death.1,2,4,5
A 2023 retrospective multicenter study involving over 2,600 hospitalized Covid-19 patients (between February 2020 and August 2022) found hyponatremia in 34.2%: Mild (Na 131-134 mmol/L) 25.1%, moderate (Na 126-130 mmol/L) 7.5% and severe (<126 mmol/L) 1.8%.3 There was a significant association between male sex at birth, hypertension, chronic kidney disease, immunosuppressives, thiazide diuretics and hyponatremia.3
Similarly, another retrospective study of hospitalized Covid-19 patients found an association between hyponatremia and several common chronic diseases, such as diabetes, hypertension, ischemic heart disease, chronic liver disease and chronic kidney disease.4 It’s important to note that since older age has also been found to be a risk factor for hyponatremia in Covid-19, the independent contribution of these conditions to hyponatremia is unclear.3
As with many other infectious diseases, the mechanism of hyponatremia in patients with Covid-19 likely has multiple causes, including hypovolemia, syndrome of inappropriate anti-diuretic hormone secretion (SIADH), diuretic use and corticosteroid deficiency, particularly in the critically ill. 1-4
Interestingly, a study performed early in the pandemic (March 2020) found that the majority (57%) of hospitalized Covid-19 patients with hyponatremic were euvolemic and that the administration of isotonic saline to such patients was independently associated with increased hospital mortality (cause unclear).2 The authors suggested closer attention to the volume status of Covid-19 patients with hyponatremia (eg, through closer attention to the jugular venous pressure on physical exam) before considering treatment with isotonic saline.
Last, Covid-19 may be associated with hyponatremia during the post-discharge period as well. An intriguing 2024 study found nearly 25% of patients with Covid-19 developed hyponatremia (<135 mmol/L) during the 1-year follow-up period after discharge with most not reported to have hyponatremia during their index hospitalization.5 In the same study, hyponatremia was associated with older age, male sex, diabetes, hypertension, heart failure, previous invasive ventilatory support and increased rate of readmission.5
Bonus Pearl: Did you know that there is an inverse relationship between interleukin-6, a key pro-inflammatory cytokine, and plasma sodium levels in Covid-19 and that this association may be stronger than that of other viral or bacterial respiratory infections?2
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References
- Ayus JC, Klantar-Zadeh K, Tantisattamo E, et al. Is hyponatremia a novel marker of inflammation in patients with Covid-19? Nephrol Dial Transplant 2023;38:1921-24. Is hyponatremia a novel marker of inflammation in patients with COVID-19? – PubMed (nih.gov)
- Pazos-Guerra M, Ruiz-Sanchez JG, Perez-Candel X, et al. Inappropriate therapy of euvolemic hyponatremia, the most frequent type of hyponatremia in SARS-CoV-2 infection, is associated with increased mortality in COVID-19 patients. Front Endocrinol 2023; 14:1227058. Inappropriate therapy of euvolemic hyponatremia, the most frequent type of hyponatremia in SARS-CoV-2 infection, is associated with increased mortality in COVID-19 patients – PubMed (nih.gov)
- De Haan L, ten Wolde, Beudel M, et al. What is the aetiology of dynatreaemia in COVID-19 and how is this related to outcomes in patients admitted during earlier and later COVID-19 waves? A multicentre, restrospective observational study in 11 Dutch hospitals. BMJ Open 2023;13:e075232. Original research: What is the aetiology of dysnatraemia in COVID-19 and how is this related to outcomes in patients admitted during earlier and later COVID-19 waves? A multicentre, retrospective observational study in 11 Dutch hospitals – PMC (nih.gov)
- Rehman F, Rehan ST, Rind BJ, et al. Hyponatremia causing factors and its association with disease severity and length of stay in Covid-19 patients: A retrospective study from tertiary care hospital. Medicine 2023; 102:45(e35920) Hyponatremia causing factors and its association with disease severity and length of stay in COVID-19 patients: A retrospective study from tertiary care hospital – PubMed (nih.gov)
- Biagetti B, Sanchez-Montalva A, Puig-Perez A, et al. Hyponatremia after COVID-19 is frequent in the first year and increases re-admissions. Scientific Reports 2024:14:595. Hyponatremia after COVID-19 is frequent in the first year and increases re-admissions – PubMed (nih.gov)
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