Blood nitrate levels in septic and cardiogenic shock

Abstract

Objective: The aims of the study were: i) to determine whether cardiogenic shock is associated with elevation of plasma nitrite (NO2-) and/or nitrate (NO3-) levels, ii) to determine whether NO2-/NO3- could be used as a predictor of the septic or cardiogenic origin of shock, and iii) to compare NO2-/NO3- plasma levels to more routinely measured inflammatory markers. Design: Prospective study. Setting: Fourteen-bed medical intensive care unit in a university hospital. Patients: Twenty-eight patients with cardiogenic (n=15) or septic shock (n=13). Measurements and main results: In the 13 septic patients, plasma NO3- levels were markedly increased (median value 143 μmol/l) and significantly higher than in patients with cardiogenic shock (32 μmol/l, p=0.0001). In cardiogenic shock, plasma NO3- levels were always below 100 μmol/l but significantly higher than those measured in 15 normal subjects (16 μmol/l, p=0.015). The best predictive value for a septic origin was obtained at the cutoff of 100 μmol/l. At this threshold, the specificity was 100% and sensitivity 64%. A comparison of the receiver operator characteristic curves constructed for nitrate and C-reactive protein values showed that nitrate was a better indicator of a septic aetiology of shock. Conclusion: In patients with circulatory shock of unclear origin, a plasma nitrate level above 100 μmol/l appears to be a reliable indicator of a septic origin. Further studies are needed to evaluate the clinical value of this test.