[Transcapillary water filtration in the presence of an increase in intravascular pressure as a factor in the development of brain edema].

The concentration of K+ and Na+ ions in the extracellular fluid of the parietal cortex of the brain was studied in experiments on rabbits ("chest-head" preparation) by means of selective electrodes during a controlled increase in general venous pressure by approximately 13 mm Hg. A decrease in the concentration of Na+ ions and mild changes in the concentration of K+ ions indicated that the extracellular fluid was diluted due to filtration of water from the blood vessels. In the normal brain this process was reversible, while in a pre-edematous condition the excess filtration of water led ultimately to the development of edema of the brain with the corresponding changes in the function of the plasma membranes and changes in the concentration of K+ and Na+ ions in the extracellular fluid.