ABSTRACT
Since the discovery of the biological existence of reactive oxygen species (e.g., free radicals or oxidants) in 1969, there has been a proliferation of reports on the chemical nature, production, and reactions of these species, as well as the description of defense mechanisms and pharmacological approaches to preventing oxidant tissue injury. There is extensive evidence that reactive species contribute to pulmonary and vascular injury in the critical care setting, but little success has been enjoyed in the application of antioxidant interventions. We will make the point in the present chapter that only recently are key mechanisms for free radical-mediated tissue injury being described. This is mainly due to the limitations imposed by the high reactivity of free radical species in preventing their tissue measurement and the only recent establishment of incisive cause-andeffect relations between oxidant stress and tissue injury. This dilemma, in turn, has impeded the development of tissue site-directed and reaction mechanismdirected strategies for potent pharmacological interventions.
