termed ‘‘idiogenic osmoles’’) that maintain cellular volume.65–67 In addition intracellular acidosis (possibly exacerbated by the passage of ketone bodies into cells as well as hypoxia) leads to intracellular sodium accumulation as hydrogen is extruded from the cells by the sodium/hydrogen membrane pump. If extracellular osmolarity falls at a rate exceeding that at which the brain can excrete its accumulated idiogenic osmoles, then oedema occurs.65–67