Intraoperative changes in somatosensory evoked potentials as predictors of perioperative stroke in carotid endarterectomy

Abstract

Intro: Perioperative stroke is a known but severe neurological complication that can occur after carotid endarterectomy (CEA). Perioperative stroke has been shown to increase the risk of morbidity and mortality in the short and long term. Intraoperative neurophysiological monitoring with somatosensory evoked potentials (SSEPs) is utilized to warn the surgical team of impending neurological deficits. Our goal for this study is to quantitatively evaluate the diagnostic value of SSEP changes in predicting perioperative stroke during CEA. Method: We identified all perioperative strokes during the hospital stay. We further classified them into major and minor strokes. To quantitatively assess SSEP changes, amplitudes and latencies of the cortical SSEP responses were measured during various critical and consistent times during CEA. Results: There is a significant difference in amplitude between controls and perioperative strokes at all time points after pre-incision, not including the end of the surgery. Patients with perioperative strokes had significantly decreased amplitude from all four baselines. The area under the curve for ROC curve analysis of pre incision amplitude change was greater than incision, heparin, and pre-clamp. A decrease greater than 50% of amplitude was predictive of perioperative stroke and major strokes alone from all baselines. Discussion: It should be considered that the purpose of an alarm is to present a warning in which an intervention is still possible to prevent the occurrence of a perioperative stroke. It should be recommended that a pre-incision baseline is used during CEA. The alarm criteria should be moved to provide an appropriate cushion to allow intervention. Latency changes were very specific but have limited sensitivity, and do not appear to be very useful, especially at the current alarm criteria of a 10% increase.