Intracranial Pressure and Regional Cerebral Blood Flow Responses to Experimental Brain Retraction Pressure

During the past four years we have been delineating the physiopathological responses of brain to forces developed on it by graded retraction pressure (1,2,3,4). We have noted that the pressure threshold for the development of histological changes after one hour of retraction at normotensive levels was greater than 20 torr and at induced hypotensive levels greater than 10 torr (2,3). We have shown the correlation of somatosensory cortically evoked responses (SER) to the development of lesions and to cerebral perfusion pressures (CPP) — with a higher CPP showing a smaller decrease in SER and greater resistance to histopathological changes (4,5). We have evaluated brain retraction pressure (BRP) changes during intracranial procedures in the human and indicated that high BRP can be generated (3) (> 125 torr). Finally, we have developed a counter pressure BRP monitoring unit that is sensitive and reliable.