VALIDITY OF SEP MONITORING IN CAROTID SURGERY - REVIEW AND OWN RESULTS

Objective. The sensitivity of intraoperative monitoring by means of so matosensory evoked potentials (SEP) in carotid surgery is to be examin ed. Experimental design. Prospective clinical investigation. In additi on, the influence of circulatory parameters on SEP curves will also be tested. Setting. Department of Surgery of a university clinic. Materi als and methods. A total of 200 patients underwent intraoperative moni toring by means of somatosensory evoked potentials (SEP) during caroti d endarterectomy between March 1, 1991 and August 1, 1994. Measures. I n order to exclude blood pressure variations as a cause for amplitude changes the blood pressure and pulse were documented during the entire phase of preparation and clamping. Results. A significant correlation could not be established between parameters of circulation and amplit ude changes (r=0.0026; p=0.62). In seven cases of intraoperative ampli tude reduction of more than 50% a stroke has been avoided by inserting a shunt. Despite the lack of an amplitude reduction, a watershed stro ke of A.cerebri media and A.cerebri posterior occurred in two instance s. Taking this into consideration the sensitivity of monitoring is 99. 0% at a specificity of 100%. Conclusions. SEP-monitoring in carotid en darterectomy is simple to execute and is superior in sensitivity to EE G analysis. To avoid artefaction by anesthesia, a standard injection a nesthesia is recommended. Farfield potentials should also be derived t o avoid watershed infarctions.