Ischemia in children

Ischemia is a pathophysiological state of hypoperfusion with cellular, local and systemic consequences that can be severe and threatening to tissue and organ function and consequently to the life of the patient. Brief ischemia may result in reversible injury with preservation of cellular integrity, and may even be protective against the harmful effects of subsequent and more prolonged ischemia. If the underlying abnormality has been corrected and perfusion restored after prolonged ischemia, reperfusion injury may occur. Reperfusion injury is caused by an imbalance between increased production of reactive oxygen and nitrogen species and decreased availability of such free-radical scavengers as nitric oxide. This results in a cascade of effects characteristic of an acute inflammatory reaction and most profoundly affecting the endothelial cells lining microscopic blood vessels. The intensity of this inflammatory reaction may extend to involvement of remote tissues and organs, leading to multiple organ dysfunction with a high degree of morbidity and mortality. When uncorrected, prolonged ischemia leads to irreversible injury: Necrosis or cell death. The final common pathway of disorganized and contiguous cell death after prolonged ischemia is indistinguishable from that evoked by other nonphysiological disturbances such as metabolic poisoning, hypoxia, trauma, lytic viruses, hypothermia and complement attack. This stands in opposition to the highly organized and tightly regulated process of programmed cell death, or apoptosis. Interestingly, damage to the cell related to ischemia or ischemia-reperfusion injury may induce cell death from apoptosis.