ObjectiveTo determine the plasma antioxidant potential of patients in the intensive care unit (ICU) with severe sepsis and secondary organ dysfunction and relate these findings to outcome.DesignA prospective, cohort study.SettingA nine-bed ICU in a university teaching hospital.PatientsFifteen consecutive patients, who were within 18 hrs of development of severe sepsis and secondary organ dysfunction.InterventionsPlasma samples were obtained within 18 hrs of the onset of secondary organ dysfunction and subsequently on days 2, 3, 4, 6, 8, 10, and 15 until patients either left the ICU or died. Plasma antioxidant potential was determined by an ultraviolet spectrophotometric technique.Measurements and Main ResultsThe mean initial plasma antioxidant potential was lower than our range for healthy volunteers (p less than .05). Survivors had an initial plasma antioxidant potential that was greater than nonsurvivors (p less than .01), and serial subset analysis demonstrated that survivors, despite having a low initial plasma antioxidant potential rapidly attained normal or supranormal values. While plasma antioxidant potential also increased in nonsurvivors over time, values in this subset never reached the normal range and remained below values in survivors at all time points studied (p less than .05).ConclusionsPlasma antioxidant potential is initially decreased in patients with sepsis who develop organ dysfunction, and it increases over time. While we have no clear evidence to prove that this reduction has a causal relationship, failure to achieve a normal plasma antioxidant potential is strongly associated with an unfavorable outcome.(Crit Care Med 1996; 24:1179-1183)