Monitoring during Carotid Surgery

Abstract

In the following prospective study of 125 carotid endarterectomies, we compared monitoring of somatosensory evoked potentials (SEPs) with carotid stump pressure (CSP) measurement in order to determine the efficacy of both methods in reliably predicting cerebral ischemia caused by cross-clamping of the carotid artery. A complete flattening of the cortical SEP was the sole criterion for selective shunting. Two patients suffered from transitory neurological deficits in the postoperative period. Both experienced complete disappearance of postcentral SEP components after carotid cross-clamping. In a further 10 cases, an intraoperative loss of SEP amplitudes occurred, but could be reversed by the insertion of a shunt or by induced hypertension. All of these patients showed a normal neurological examination postoperatively as did all of the patients with identifiable SEPs after cross-clamping. In all of the 12 patients with complete flattening of the cortical waveform, we found CSP levels less than 50 mm Hg. A further 61 patients had a CSP less than 50 mm Hg, but neither an intraoperative loss of SEP amplitudes nor postoperative neurological deficits were detected in any of these patients. We conclude that, in contrast to CSP, SEPs not only help to identify patients with insufficient collateral blood flow who benefit from specific cerebral protection, but also to avoid improper and hazardous application of these measures in patients with sufficient cerebral perfusion.