Fig. (2) The nitric oxide (NO), nitrite (NO₂^-) and nitrate (NO₃^-) cycle. Formation of NO, oxidation to nitrite and nitrate (collectively, NOx), and their potential as biomarkers for disease processes in the acute care setting. Acute kidney injury (AKI); Cerebrospinal fluid (CSF); Central nervous system (CNS); Cyclic guanylate monophosphate (cGMP); Fractional excretion of nitric oxide (feNO); Guanylate triphosphate (GTP); Nitric oxide synthase (NOS); Soluble guanylate cyclase (sGC).