High serum nitrates levels in non-survivor COVID-19 patients

Abstract

ObjectiveHigher blood nitrate and nitrite levels have been found in coronavirus disease 2019 (COVID-19) patients than in healthy subjects. The present study explores the potential association between serum nitrate levels and mortality in COVID-19 patients. DesignA prospective observation study was carried out. SettingEight Intensive Care Units (ICUs) from 6 hospitals in the Canary Islands (Spain). PatientsCOVID-19 patients admitted to the ICU. InterventionsDetermination of serum nitrate levels at ICU admission. Main variable of interestMortality at 30 days. ResultsNon-surviving (n=11) compared to surviving patients (n=42) showed higher APACHE-II (p<0.001) and SOFA scores (p=0.004), and higher serum nitrate levels (p=0.001). Logistic regression analyses showed serum nitrate levels to be associated to 30-day mortality after controlling for SOFA (OR=1.021; 95%CI=1.006–1.036; p=0.01) or APACHE-II (OR=1.023; 95%CI=1.006–1.041; p=0.01). There were no differences in the area under the curve (AUC) for mortality prediction by serum nitrate levels (AUC=83%; 95%CI=73–92%; p<0.001), APACHE II (AUC=85%; 95%CI=75–96%; p<0.001) and SOFA (AUC=78%; 95%CI=63–92%; p=0.005) based on the DeLong method. The Kaplan–Meier analysis found patients with serum nitrates levels>68.4μmol/l to have a higher mortality rate (hazard ratio=138.8; 95%CI=22.3–863.9; p<0.001). ConclusionsThe main novel finding was the association between serum nitrate levels and mortality in COVID-19 patients controlling for the SOFA or APACHE-II scores, though larger studies are needed to confirm this observation.