Somatosensory evoked potentials versus locoregional anaesthesia in the monitoring of cerebral function during carotid artery surgery: Preliminary results of a prospective study

Objective: to relate changes in somatosensory-evoked potentials (SEPs) with onset of neurological deficits in patients having carotid endarterectomy ( CEA) under locoregional anaesthesia. Methods: a prospective study of 50 consecutive patients. Results: SEPs yielded an accuracy of 98%, specifcity 100%, and sensitivity 89%. In all concordant cases the onset of a neurological deficit in awake p atients corresponded to a 30-40% reduction in amplitude of N20-P25 waveform s. After shunting, the N20-P25 took 2-3 min to return to normal. Conclusions: SEPs are associated with a 2% false negative rate. Their thres hold for detecting cerebral ischaemia is lower than the currently reported value for patients under general anaesthesia. The time needed for evoked po tentials (2-3 min) to return to normal after shunting limits their usefulne ss in verifying effective shunting.