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

Abstract

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%, specificity 100%, and sensitivity 89%. In all concordant cases the onset of a neurological deficit in awake patients corresponded to a 30-40% reduction in amplitude of N20-P25 waveforms. After shunting, the N20-P25 took 2-3 min to return to normal. Conclusions: SEPs are associated with a 2% false negative rate. Their threshold for detecting cerebral ischaemia is lower than the currently reported value for patients under general anaesthesia. The time needed for evoked potentials (2-3 min) to return to normal after shunting limits their usefulness in verifying effective shunting.