Histochemical characterization of cytotoxic brain edema. Potassium concentrations after cerebral ischemia and during the postmortem interval

Cytotoxic edema is a phenomenon of the ischemically damaged brain. In the p resent study we tested a histochemical method that detects this phenomenon based on potassium (K+) levels in the brain. In a first series focal cerebr al ischemia was induced by arterial occlusion in 23 gerbils (Meriones ungui culatus). After survival times of 30, 60 and 120 min, the animals were kill ed and brain section histochemically stained for potassium and quantitative ly evaluated with a morphometric method. The results were compared with tho se using physicochemical techniques. A distinct K+ depletion could be demon strated in the area of the focal ischemia within a survival time of 30 min, the depletion growing therafter with increasing survival time. In a second series histochemical and chemical methods were used to study the stability of K+ levels in undamaged brains of IS healthy rats during postmortem inte rvals of 2.5 and 5 h. Within these intervals K+ levels were clearly deplete d, apparently as a result of cerebral spinal fluid (CSF) diffusion. Even if neuronal injury can be demonstrated histochemically after very brief survi val times of about 30 min, postmortem storage of the cadavers rendered dete ction impossible due to electrolyte and water diffusion. In autoptic human cases, therefore, this technique is of no practical utility in detecting cy totoxic brain edema in postmortem tissue.