Biomarkers of oxidative stress in critically ill patients: what should be measured, when and how?

This review is dedicated to updating the knowledge on oxidative stress in critically ill patients with an intense inflammatory reaction, and to link it with recent findings supporting the possible involvement of oxidative injuries in systems and organs that frequently fail in the critically ill.

Some direct or indirect biomarkers of oxidative stress have been validated in critically ill patients, and further support the major role of oxidative stress in these conditions.

The assessment of oxidative stress, defined as the association between an increased production of oxygen-derived species and an exhaustion of the stores of antioxidants, requires a multimodal approach. Oxidative damage itself can be much better estimated by quantifying the oxidative byproducts of the lipids and proteins associated with an evaluation of the remaining stores of the corresponding functional antioxidants, or the activity of antioxidant enzymes, than by global tests of the total oxidative damage or the total antioxidant stores. Recent clinical data confirm an important role of increased oxidative stress in the acute dysfunctions of the respiratory, renal and cerebral systems.