THE EFFECT OF LESION VOLUME ON CEREBRAL VASOMOTOR TONE AFTER FOCAL BRAIN INJURY AND SHOCK

We have previously shown that the volume of a focal brain injury influ ences cerebral blood flow, We hypothesized that the cerebral vasomotor tone after traumatic brain injury and shock is related to lesion volu me and that the size of the lesion would affect vasomotor reactivity. Swine were randomized to receive either a large or small cryogenic inj ury followed by shock, and were studied for 5 h postresuscitation, A s mall brain injury and shock produced a significant and sustained incre ase in bihemispheric pial arteriolar diameter when compared to the lar ge lesion group and controls, A large brain injury and shock resulted in a significant decrease in the pial arteriolar diameter in the injur ed hemisphere, We also noted significant differences between and withi n groups in interhemispheric pial arteriolar diameter and pial arterio lar reactivity to acetylcholine and hypocarbia. These data suggest tha t the volume of injured tissue influences cerebral blood flow by a vas cular mechanism, which may be due in part to an alteration in cerebral endothelial cell function.