Mannitol, Intracranial Pressure, and Vasogenic Edema - Essay Example

Mannitol is applied clinically for osmotherapy in order to decrease intracranial pressure until other treatment options can be applied (Battison, Andrews, Graham, and Perry, 2005).  It is a drug that helps facilitate the introduction of drugs directly into the brain.  The blood-brain barrier is very selective in its functions and would normally not allow for the introduction of drugs or any other chemicals into the brain.  There is a need for active transport processes which would call for the use of energy (Battison, et.al., 2005).  Mannitol can open the barrier by reducing the size of the endothelial cells, and then also stretching the closed junctions.  Water then would exit the cell and enter the artery in order to facilitate osmotic balance (Vialet, Albanese, Thomachot, and Antonini, 2003).  Water loss would lead to cells shrinking.  The opened gap would peak after five minutes following mannitol administration.  At this point, drugs are introduced into the artery and the brain.  

The impact of mannitol in decreasing intracranial pressure has caused its widespread use in neurosurgery (Lawson, 2007).  In general, the impact has been credited to the hyper-osmotic impact of mannitol which causes the extraction of water from the swollen brain.  However, this pharmacological action has been put at issue due to different observations (Lawson, 2007).  One is that there is a decrease in intracranial pressure prior to any reduction in white matter content.  Another is based on the observation that where the intracranial pressure is significantly decreased, there is no major shift in the white water content (Cruz, Minoja, and Okuchi, 2001).  Intracranial pressure also stays high even with a decrease in white matter water with the administration of intravenous albumin. Author Hartwell (1993) discussed that soon after mannitol has been transfused, there was a slight rise in white matter water content.