Nitric oxide indices in human septic shock

Objectives: To study the relation between nitrite, nitrate, nitrotyrosine, and nitrosothiols as NO indices in human septic shock. Design: A prospective clinical study. Setting: Intensive care units in a university hospital and a central county hospital. Patients: Sixteen patients admitted for septic shock. Nine healthy voluntee rs served as controls. Interventions: None. Measurements and Main Results: Patients with septic shock had a hyperdynami c circulatory response and required infusion of at least two vasopressors t o maintain systemic blood pressure. Four episodes of recurrent shock occurr ed in two patients. Heparinized plasma was collected once daily for analysi s of NO indices. Peak plasma concentrations of nitrite + nitrate (NOx) were elevated in first episodes of septic shock; 144 +/- 39 mu M vs. controls, 20 +/- 3 mu M (p < .05). Peak plasma NOx concentrations in recurrent shocks were; 160 +/- 19 mu M. Peak plasma concentrations of 3-nitrotyrosine (NT) were elevated in primary septic shock 102 +/- 19 pmol.ml(-1) vs. controls 1 4 +/- 6 pmol.ml(-1) (p < .05), Peak NT concentrations were 117 +/- 37 pmol. ml(-1) in recurrent septic shock. Peak plasma NT concentrations did not coi ncide with peak NOx concentrations in half of the episodes of septic shock. Plasma NT was elevated (59 +/- 15 pmol.ml(-1) vs. controls 14 +/- 6 pmol.m l(-1), p < .05) in patients with normal plasma NOx concentrations throughou t septic shock. Plasma concentrations of nitrosothiols did not change durin g septic shock. Conclusions: Plasma concentrations of NOx and NT are elevated in primary ep isodes of septic shock and may also be elevated in secondary septic shock, but too few episodes of recurrent septic shock occurred to allow firm concl usions. Plasma concentrations of NT are elevated in patients with septic sh ock with normal plasma NOx concentrations, indicating that plasma concentra tions of NOx may not always accurately reflect MO production. Reactive nitr ogen species may be formed in septic shock, and measuring both NOx and NT m ay give a better indication of MO production in septic shock than NOx alone . Plasma levels of nitrosothiols did not change during septic shock. (Crit Care Med 2000; 28:2779-2785).