CEREBRAL BLOOD-FLOW DURING CAROTID ENDARTERECTOMY DETERMINED BY 3-DIMENSIONAL SPECT MEASUREMENT - RELATION TO PREOPERATIVE RISK ASSESSMENT

Cross-clamping of the carotid artery during carotid endarterectomy implies a risk of developing an ischaemic insult. To evaluate the effects of carotid artery occlusion on cerebral blood flow (CBF), both hemispheric and regional CBF (rCBF) were investigated using intravenously (i.v.) administered 133Xenon with 3 min clearance recording time for two-dimensionally (hemispheric CBF) and 99m-technetium-hexamethylpropylene amine oxime (99mTC-HMPAO) for three-dimensionally single photon emission computed tomography (SPECT) measurements (rCBF). Thirteen patients scheduled to undergo carotid endarterectomy anaesthetised with fentanyllisoflurane participated in the study. Preoperative evaluation included investigation of rCBF with SPECT in all participants. Two intraoperative 133Xe CBF measurements were performed in each patient, before and after occlusion of the carotid artery. The preoperative rCBF measurement constituted the reference, for technical reasons, for the intraoperative investigations of rCBF during cross-clamping, which was completed immediately after the hemispheric measurements. The increase in preoperative risk evaluation as described by Sundt et al. and modified by Cho et al. corresponded excellently to a decrease in hemispheric CBF due to cross-clamping. A significant decrease in rCBF (p < 0.005) was present between patients with high and low preoperative risk score for the region of the middle cerebral artery. In this region, a correlation between decrease in rCBF and corresponding decrease in hemispheric CBF was also present. The present study demonstrates that the vascular regions of the ipsilateral middle cerebral artery are the most vulnerable vascular area during cross-clamping in individuals with high preoperative risk score. The results also indicate that the i.v. 133Xe method with 3 min clearance monitoring for measurements of hemispheric CBF gives adequate information for detection of potential ischaemia during carotid endarterectomies even under circumstances with changing blood flow. © 1993 Grune & Stratton Ltd.