Effects of preexisting bypass graft on rCBF and SSEP's following acute stroke in XXXX .

@entity235 @entity1317 @entity455 @entity63
Regional cerebral blood flow (rCBF) was measured with radiolabeled microspheres in a @entity235 model of superficial temporal artery-middle cerebral artery (STA-MCA) bypass and acute @entity63 . Ischemic zone flows in seven @entity235 with the bypass first closed and then open showed no significant contribution of bypass flow in the intact vascular system. Following acute proximal occlusion, rCBF was preserved by bypass flow. A significant flow decrease ensued when the bypass was then clipped, confirming the adequacy of the lesion and the protective effect of the bypass. Reopening the bypass after 15 minutes of @entity63 restored 76% of the previous flow. This was a significant increase from the global @entity63 values, and was not statistically different from preocclusive values. Preocclusion somatosensory evoked potentials (SSEP's) in these animals showed a consistent biphasic wave at 8 to 10 msec after stimulation. This wave, with some decrease in amplitude, was preserved by bypass flow following creation of the @entity455 . Bypass clipping abolished these ipsilateral SSEP's. Variable return of SSEP's occurred following reopening of the graft, but the recordings never reached preischemic amplitudes. This experimental study shows that, in this model, a prophylactic bypass subjected to immediate demand (with no time for "maturation") can adequately augment cortical rCBF and is superior to delayed revascularization. The data lend theoretical support to placement of a prophylactic STA-MCA bypass prior to elective carotid artery sacrifice or in surgery where the risk of acute @entity1317 is high.
