Phasic Recognition of Edema Caused by Ischemia

Brain edema is associated with an accumulation of water in brain tissue. Therefore, common mechanisms may exist with regard to the pathogenesis of disturbances of cell metabolism due to a restriction of blood supply and an impairment of osmoregulation. However, accumulation of water in brain tissue commences only — after ischemia, when circulation is reestablished8. Although there is little doubt that it is the ischemic insult which triggers the mechanisms of edema formation, the different factors involved in the proces of edema formation have not been precisely identified yet. On the other hand, the fact that many compounds and factors are suggested to be involved in the development of brain edema may indeed uncover our ignorance of the basic mechanisms of ischemic brain edema1,7. It is widely held, that development of energy failure secondary to the restriction of blood flow causes breakdown of ionic pumps resulting in an intracellular accumulation of Na+, and consequently of water, leading to cell swelling. However, this notion may be in conflict with the findings mentioned above on experimental stroke in gerbils that edema evolves during post-ischemic recirculation, i.e. when cerebral blood flow is already established again and the energy reserves restored6,7.