AUTHOR=Ayus Juan Carlos , Negri Armando Luis , Moritz Michael L. , Lee Kyung Min , Caputo Daniel , Borda Maria Elena , Go Alan S. , Eghi Carlos 

TITLE=Hyponatremia, Inflammation at Admission, and Mortality in Hospitalized COVID-19 Patients: A Prospective Cohort Study

JOURNAL=Frontiers in Medicine

VOLUME=Volume 8 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2021.748364

DOI=10.3389/fmed.2021.748364

ISSN=2296-858X

ABSTRACT=Background Systemic inflammation has been associated with severe COVID-19 disease. Hyponatremia can result from inflammation due to non-osmotic stimuli for vasopressin production.  
Methods: We prospectively studied 799 patients hospitalized with COVID-19 between March 7 and November 7, 2020, at Hospital Posadas in Buenos Aires, Argentina in order to evaluate the association between hyponatremia, inflammation and its impact on clinical outcomes. Admission biochemistries, high-sensitivity C-reactive protein (hsCRP), ferritin, patient demographics, and outcome data were recorded.  Outcomes (within 30 days after symptoms) evaluated included ICU admission, mechanical ventilation, dialysis-requiring AKI, and in-hospital mortality. Length of hospital stay (in days) and hospital readmission for any cause within 30 days after discharge were evaluated using comprehensive data from the EHR.
Results: Hyponatremia (median Na =133 mmol / L) was present on admission in 366 (45.8%). Hyponatremic patients had higher hsCRP (median 10.3 [IR 4.8-18.4] mg/dl vs 6.6 [IR 1.6 – 14.0] mg/dl, p< 0.01) and ferritin levels (median 649 [IQR 492-1168] ng/dl vs 393 [IQR 156-1440] ng/dl, p = 0.02) than normonatremic patients. Hyponatremia was associated with higher odds of an abnormal hsCRP (unadjusted OR 5.03, 95%CI:2.52-10.03), and remained significant after adjustment for potential confounders (adjusted OR 4.70 [95%CI:2.33-9.49], p<0.01). Hyponatremic patients had increased mortality on unadjusted (HR 3.03, 95%CI:2.13-4.31) and adjusted (HR 2.48, 95%CI:1.70-3.63) in Cox proportional hazard models.  Crude 30-day survival was lower for patients with hyponatremia at admission (mean [SD] survival 22.1 [0.70] days) compared with patients who were normonatremic (mean [SD] survival 27.1 [0.40] days, p < 0.01).
Conclusion: Mild hyponatremia on admission is common, is associated with systemic inflammation and is an independent risk factor for hospital mortality. (www.ClinicalTrials.gov Identifier: NCT04493268)