Osmotic Dehydrating Agents Reduce Intracranial Pressure After Severe Head Injuries Mainly Through Vasoconstriction

Abstract

It is generally thought that mannitol and other so-called osmotic agents such as urea and glycerol act through extraction of water from the cerebral extracellular space into the intravascular compartment by induction of a difference in osmotic pressure between the blood and the brain. It has remained unclear, however, whether water is better extracted from edematous brain [1, 24] or from normal brain [6, 10], and there is even evidence that there may be hardly any influence at all exerted upon brain water content according to measurements performed with the very sensitive specific gravity technique [23]. Moreover, a clear relationship between changes in brain water content and intracranial pressure (ICP) has not always been shown with the use of osmotic agents [1, 10, 22].