Monitoring of somatosensory evoked potentials during carotid endarterectomy: relationship with different haemodynamic parameters and clinical outcome.

The authors studied the changes of Somatosensory Evoked Potentials (SEPs) performed in 241 anaesthetised patients during 264 carotid endarterectomies (CEs). SEP responses were considered significantly modified when the central conduction time was greater than 1 ms and/or when the amplitude of the complex N20-P25 decreased by at least 50%. Both CCT and N20-P25 have been correlated with different parameters, including the presence or absence of preoperative neurological deficits, the type of general anaesthesia, the status of the contralateral and the ipsilateral carotid artery, stump pressure, the use of an intraluminal shunt and the perioperative results. After carotid cross-clamping SEP responses were within the normal range in 236 CEs (89%), and abnormal in 28 (11%). A shunt was inserted 23 times in 264 (9%) cases. None of the patients operated on in this series experienced a permanent neurological deficit; there were three (1.1%) transient deficits (two Rinds and one TIA) and two deaths from non-neurological causes. Only one of the transient deficits was present when the patient woke from the anaesthetic and this event was predicted by significant modification of the SEP which did not reverse after removal of the clamps (a shunt was not used). None of the patients in our series who did not present significant modifications of SEPs during the operation had any postoperative neurological deficit. The authors conclude that SEP recording is a highly reliable and objective method for continuous monitoring of brain function during CE.