[Oxygen metabolism and toxicity in the phenomenon of ischemia-reperfusion]

One of the major cause of human disease results from the compromise of blood flow and oxygen delivery to tissues. Ischemia phenomenon is defined as blood flow that is inadequate to maintain normal tissue function. Prolonged ischemia ultimately results in irreversible changes in cell metabolism and cell death. Historically, it was felt that if ischemia results in altered cell function and injury, then reoxygenation or reperfusion leading to a restoration of a normal blood flow was expected to have a beneficial effect and promote salvage of tissue depending on the extent of ischemia. Recent studies have, however, revealed that reoxygenation leads to an oxygen metabolism resulting in the generation of active and toxic oxygen intermediates (free radicals) which play an important role in the pathophysiology of reperfusion injury.