Effects of glycerol administration on experimental brain edema

The effects of glycerol on brain water and solute distribution in cerebral edema are not well known. In brail edema induced in dogs by focal freezing, tissue underlying the necrotic lesion had an elevated water content but the remainder of the brain was unaltered. Administration of glycerol to maintain plasma glycerol at about 35 mM dehydrated normal white matter, but water and solute contents of the edematous white matter were not changed. During the initial 3 hours of glycerol infusion, CSF pressure fell, but when the infusion was continued for 6 hours or more, a gradual rise in CSF pressure was observed. In three animals, the final CSF pressure was higher than preinfusion values. At this time, brain water content was significantly less than normal, but both CSF osmolality and glycerol concentration were higher than plasma. The data show that glycerol infusion can decrease intracranial volume towards normal by dehydration of normal, but not damaged, brain tissue. The rebound rise in CSF pressure observed during the continuous administration of glycerol cannot be explained by rehydration of brain tissue but may be related to alterations in CSF dynamics.