COVID-19 and hyponatremia

COVID-19 is an ongoing pandemic infectious disease determined by a new coronavirus, severe acute respiratory syndrome coronavirus (SARS-CoV-2). The severity spectrum of the clinical manifestations of the disease is variable, from almost asymptomatic cases to critical, fatal cases. The clinical manifestations usually include fever, dry cough, dyspnea, muscular symptoms, headache, sore throat, diarrhea, nausea/vomiting, abdominal pain, fatigue, loss of smell or taste.

The laboratory tests in patients with COVID-19 may reveal lymphopenia, increased aminotransferases, high lactate dehydrogenase, inflammatory syndrome (high C-reactive protein, erythrocyte sedimentation rate, fibrinogen), coagulation tests abnormalities. There are recent reports and small studies that reported an association between COVID-19 and hyponatremia (serum natrium < 135 mEq/L) (1). A few case reports described patients with COVID-19 with only symptoms of hyponatremia(2). The etiology of hyponatremia in patients with COVID-19 is likely to be multifactorial and its early etiologic diagnosis may be extremely important for the evolution of the disease. For a correct diagnosis and treatment, measurement of plasma and urine osmolality is always necessary. An appropriate treatment of hyponatremia may be even more important in hospitalized patients with COVID-19, in whom an inadequate fluid and electrolyte management may increase the risk for respiratory and/or cardiac complications.

What could be the causes of hyponatremia in COVID-19 patients? Hyponatremia may be due to the increased release of antidiuretic hormone (ADH) because of gastrointestinal fluid losses (diarrhea, vomiting) or low oral fluid intake, but also to the syndrome of inappropriate ADH secretion (SIADH) induced by pneumonia, respiratory insufficiency or other comorbidities. SIADH is characterized by euvolemic hyponatremia (natrium <135 mEq/L), low serum osmolality (<280 mosmol/Kg H2O), high urine osmolality (>100 mosmol/Kg H2O), increased urine natrium (>40 mmol/L), hypouricemia, in the absence of other causes of hyponatremia. Apart from pneumonia, that is frequent in patients with COVID-19, other causes of SIADH may be psychological and physical distress induced by the disease (with activation of the cortical neurons and increased hypothalamic secretion of ADH), and also the cytokine storm (with lesions of the pulmonary tissue that can induce SIADH and/or the non-osmotic release of ADH stimulated by interleukin-6)(3). The measurement of serum and urine osmolality will help the differential etiological diagnosis and will ensure a proper fluid and electrolyte management, to prevent further deterioration of these patients(4).
The association of COVID-19 with hyponatremia needs to be further identified and explored. Until then, a careful approach may be that febrile patients presenting with hyponatremia should be isolated and tested for SARS-CoV-2 infection.

Correspondence address:
Camelia C. DIACONU
email: drcameliadiaconu@gmail.com