Early post-ischemic hyperemia on transcranial cerebral oxygen saturation monitoring in carotid endarterectomy is associated with severity of cerebral ischemic insult during carotid artery clamping

Background and objective: In animal models, the magnitude of early post-ischemic hyperemia tends to correlate with the duration and intensity of prior ischemic insult. The aim of this study was to determine whether early post-ischemic hyperemia in human brain during carotid endarterectomy (CEA) is associated with the severity of cerebral ischemic insult during clamping of the internal carotid artery (ICA). Methods: Transcranial cerebral oxygen saturation using near-infrared spectroscopy was monitored intraoperatively in 171 patients undergoing CEA for ipsilateral ICA stenosis (>70%) to assess the intensity of cerebral hemispheric ischemia during ICA clamping and the magnitude of early post-ischemic hyperemia after ICA declamping. Results: Early post-ischemic hyperemia peaked within 3 minutes after ICA declamping and resolved at 20 minutes after ICA declamping. A significant correlation was observed between the magnitude of early post-ischemic hyperemia and the intensity of cerebral ischemia (r=0.697; p<0.0001). Eight patients recovered from anesthesia with a new minor neurological deficit on the side contralateral to the CEA (4.7%). Analysis by receiver operating characteristics (ROC) curve was used to estimate the ability to discriminate between patients with and without postoperative development of new neurological deficits. Area under the ROC curve was significantly greater when analysing the magnitude of early post-ischemic hyperemia (1.00; 95% CI: 0.99-1.00) when compared with the intensity of cerebral ischemia (0.93; 95% CI: 0.89-0.98) (p<0.01). Conclusion: Early post-ischemic hyperemia in CEA is correlated with the severity of cerebral ischemic insult during clamping of the ICA. [Neurol Res 2009; 31: 728-733]