Cerebral ischemia during carotid artery cross-clamping: Methods of diagnosis and prevention

A serious complication in carotid endarterectomy (CEA) is the occurrence or aggravation of neurological deficits caused by insufficient collateral cer ebral blood flow during cross-clamping. At the moment, patients with failur e of collateral circulation at this point cannot be identified preoperative ly. Thus, intraoperative monitoring and methods to prevent clamping-related cerebral ischemia are required. To put this strategy into clinical practice there are several methods of mo nitoring cerebral function (e.g. surgery performed in awake patients, elect roencephalography, somatosensory evoked potentials), changes of hemodynamic (e.g. carotid stump pressure, transcranial Doppler ultrasonography) or met abolic parameters (e.g. jugular bulb oximetry or transcranial oximetry). One technique that meets nearly all requirements of an ideal monitoring und er general anesthesia is the use of somatosensory evoked potentials (SEPs). Registration of SEPs is simple to perform and indicates with a high sensit ivity and specifity critical cerebral hypoperfusion during cross-clamping. Thus, SEPs monitoring indicates the necessity of shunt placement. As a resu lt, the use of an indwelling shunt as the most effective method to prevent clamping ischemia can be limited to selected cases, avoiding the risks of s hunting in patients with sufficient collateral flow. In addition, correct s hunt function is immediately indicated by recovering potentials. Whether a combination of SEPs with transcranial Doppler measurements will b e successful to provide additional information about cerebral embolisation should be determined.