Measures of total free radical activity in critically ill patients

Objectives: To examine the role played by free radicals during the initial phase of critical illness in patients on an Intensive Care Unit (ICU). Design and Methods: Serum total antioxidant status (TAS) and uric acid (UA) levels were measured in 50 patients over 18 hours to represent the initial stage of critical illness. Clinical scoring systems (APACHE II and multiple organ dysfunction scores) were used to assess the degree of organ dysfunction. Outcome was assessed according to patient survival (survivors, n = 36; non-survivors, n = 14). Results: Serum TAS was higher in non-survivors; a similar finding was demonstrated for serum UA. Levels of both biochemical markers were associated with the degree of organ function and with higher antioxidant and UA levels present in patients with more severe organ dysfunction. In addition, serum UA was significantly correlated to serum TAS and probably accounted for much of the antioxidant activity observed. Conclusions: The increased TAS and UA levels observed may simply be a response to the degree of renal dysfunction observed as those patients with worse renal function had higher TAS and UA levels. In conclusion, measurement of serum TAS appears to be a reflection of UA concentration and results should be interpreted with caution particularly in patients who have renal dysfunction. Copyright (C) 1999 The Canadian Society of Clinical Chemists.