Objective Higher 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… Click to show full abstract
Objective Higher 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. Design A prospective observation study was carried out. Setting Eight Intensive Care Units (ICUs) from 6 hospitals in the Canary Islands (Spain). Patients COVID-19 patients admitted to the ICU. Interventions Determination of serum nitrate levels at ICU admission. Main variable of interest Mortality at 30 days. Results Non-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 > 68.4 μmol/l to have a higher mortality rate (hazard ratio = 138.8; 95%CI = 22.3–863.9; p < 0.001). Conclusions The 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.
               
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