Accuracy of different methods in monitoring cerebral ischemia in patients undergoing carotid endarterectomy: comparison of SSEPs, MEPs, rSO2 and multimodal monitoring

Abstract

Objective To compare the accuracy of somatosensory evoked potentials(SSEPs), motor evoked potentials(MEPs), regional cerebral oxygen saturation(rSO2)and multimodal monitoring in monitoring cerebral ischemia in patients undergoing carotid endarterectomy(CEA). Methods Eighty American Society of Anesthesiologists physical status Ⅱ or Ⅲ patients of both sexes, aged 46-76 yr, scheduled for elective CEA, were enrolled in the study.SSEPs, MEPs and rSO2 were monitored during CEA.The event of intraoperative cerebral ischemia was defined as: (1)SSEP escape latency prolongation of 10% and/or amplitude decrease of 50%; (2)disappearance of MEP amplitude; (3)decrease in rSO2>20% of the baseline value; (4)When multimodal monitoring was applied, the event of intraoperative cerebral ischemia could be defined as long as one variable previously described met the condition.The gold standard of perioperative cerebral ischemia was defined as: (1)the National Institutes of Health Stroke Scale score≥4 at 1, 3 and 5 days after operation than before operation was considered as neurological dysfunction; (2)cranial CT showed a new ipsilateral cerebral focal ischemia, and postoperative intracranial hemorrhage diseases were excluded. Results Five cases developed cerebral ischemia after operation.The sensitivity and specificity of SSEPs in predicting cerebral ischemia were 80% and 83%, respectively; MEPs 80% and 80%, respectively; SSEPs+ MEPs 100% and 79%, respectively; rSO2 60% and 93%, respectively; SSEPs+ MEPs+ rSO2 100% and 7%, respectively.Decrease in rSO2 > 20% of the baseline value was consistent with SSEP escape latency prolongation of 10% and/or amplitude decrease of 50% in diagnosis of cerebral ischemia(Kappa value 0.67, P 20% of the baseline value was consistent with disappearance of MEP amplitude in diagnosis of cerebral ischemia(Kappa value 0.54, P<0.01). Conclusion rSO2 has a good agreement with SSEPs and MEPs in diagnosis of cerebral ischemia during CEA; combination of SSEPs and MEPs produces better accuracy in monitoring cerebral ischemia. Key words: Carotidendarterectomy; Evoked potentials; Oxygen; Brain ischemia