Protocol for electrophysiological monitoring of carotid endarterectomies

Abstract

Near zero stroke rates can be achieved in carotid endarterectomy (CEA) surgery with selective shunting and electrophysiological neuromonitoring. though false negative rates as high as 40% have been reported. We sought to determine if improved training for interpretation of the monitoring signals can advance the efficacy of selective shunting with electrophysiological monitoring across multiple centers, and determine if other factors could contribute to the differences in reports. Processed and raw beta band (12.5-30 Hz) electroencephalogram (EEG) and median and tibial nerve somatosensory evoked potentials (SSEP) were monitored in 668 CEA cases at six surgical centers. A decrease in amplitude of 50% or more in any EEG or SSEP channel was the criteria for shunting or initiating a neuroprotective protocol. A reduction of 50% or greater in the beta band of the EEG or amplitude of the SSEP was observed in 150 cases. No patient showed signs of a cerebral infarct after surgery. Selective shunting based on EEG and SSEP monitoring can reduce CEA intraoperative stroke rate to a near zero level if trained personnel adopted standardized protocols. We also found that the rapid administration of a protective stroke protocol by attending anesthesiologists was an important aspect of this success rate.

Keywords: carotid; carotid endarterectomy; electroencephalogram; intraoperative monitoring; somatosensory evoked potentials.

Fig. 1. Raw carotid endarterectomy.

A: before an ischemic event. B: during an ischemic event. C: during recovery from an ischemic event.

Fig 2. Ten min of compressed spectral array of beta activity.

A: compressed spectral array of F3-C3,F7-T7 and T3-T5. B: compressed spectral array of F4-C4, F8-T4 and T4-T6. a: the start of an ischemic event. b: the start of recovery.

Fig 3. Cortical somatosensory evoked potentials.

A: before an ischemic event. B: during an ischemic event. C: during recovery from an ischemic event.