Carotid endarterectomy

With regard to the international literature, there still is no clear evidence about which monitoring technique is superior in patients undergoing carotid endarterectomy (CEA) under general anesthesia. This article is supposed to discuss the issue of cerebral ischemia during internal carotid artery (ICA) cross-clamping according to the recent opportunities in the field of intraoperative neurophysiology. CEA is an effective intervention to prevent strokes in patients with symptomatic and asymptomatic carotid stenosis, but it also has a potential risk of perioperative stroke. Therefore selective shunt application based on different criteria evaluating the patient while awake or anesthetized has been shown to be sufficient in reducing the rate of perioperative stroke. Concerning neurophysiologic methods, the recording of somatosensory evoked potentials (SEPs) after electrical stimulation of the median nerve became the gold standard monitoring technique during CEA in many institutions worldwide. Otherwise, monitoring of the electroencephalogram (EEG)—essentially more channel EEG—is a common technique used during CEA, since 1993 it has been officially recommended in the United States since. Regardless to the limitations of the EEG monitoring in anesthetized CEA, the evaluation of SEPs was also shown to produce up to 3.5% false-negative results. However, both EEG and SEP are indirect predictors for cerebral ischemia providing more or less information about global ischemic events. Since monitoring of motor EPs (MEPs) provides direct information about the integrity of the corticospinal tract (CST), it was successfully implemented in aneurysm surgery more than a decade ago. Since pathophysiology during CEA can be similar, MEP monitoring was introduced in carotid surgery to detect subcortical ischemia of the CST during ICA cross-clamping. Recently published trials suggest a focal ischemia of the CST in about 1.5%–3%. Further studies supported the useful implementation of MEP method in addition to SEP recording during CEA to reduce false-negative results. Hereby the differentiation between cortical and subcortical ischemia seems pathophysiological wise essential. However, prospective investigations including a control group without MEP monitoring would be necessary to provide clear evidence.