ObjectiveTo determine antioxidant vitamin concentrations, lipid peroxidation, and an index of nitric oxide production in patients in the intensive care unit (ICU) with septic shock and relate the findings to the presence of secondary organ failure.DesignA prospective, observational study.SettingA nine-bed ICU in a University teaching hospital.Patients90 beats/min); e) shock (systolic pressure <90 mm Hg) or receiving inotropes. Fourteen patients also had secondary organ dysfunction.InterventionsNone.Measurements and Main ResultsAntioxidant vitamin concentrations were significantly lower in the patients than the reference range obtained from a comparable group of healthy controls. The mean plasma retinol (vitamin A) concentration was 26.5 +/- 19.3 micro gram/dL compared with 73.5 +/- 18.3 micro gram/dL in healthy subjects (p < .01). Additionally, 13 (81%) patients had retinol values below the lower limit of our reference range (<37.0 micro gram/dL). Tocopherol (vitamin E) plasma concentrations were below the reference range in all patients (<9.0 mg/L), with a mean value of 3.6 +/- 2.0 mg/L compared with 11.5 +/- 1.3 mg/L in healthy subjects (p < .001). Plasma beta carotene and lycopene concentrations were undetectable (<15 micro gram/L) in eight (50%) patients, and below our reference range (<101 micro gram/L and <154 micro gram/L, respectively) in the remaining patients. In the five patients with three or more dysfunctional secondary organs, plasma thiobarbituric acidreactive substances were significantly increased (p < .05), suggesting increased lipid peroxidation. Concentrations of thiobarbituric acidreactive substances correlated negatively with both plasma retinol and plasma tocopherol (r2= .42, p < .01 and r2= .48, p < .005, respectively). In the five patients from whom we were able to collect urine, nitrite excretion was increased approximate 400-fold (p < .001).ConclusionsThese data indicate decreased antioxidant status in the face of enhanced free radical activity, and suggest potential therapeutic strategies involving antioxidant repletion.(Crit Care Med 1995; 23:646-651)