The Relationship between Carotid Stump Pressure and Changes in Motor-Evoked Potentials in Carotid Endarterectomy Patients.

Abstract

Background The threshold of ischemic tolerance has not been completely identified in human clinical studies. Distal carotid artery pressure can be easily measured through the internal shunt tube during carotid endarterectomy (CEA). To confirm the critical threshold of intracranial arterial pressure and its maximum duration, we investigated the distal internal carotid artery (ICA) pressure and motor-evoked potential (MEP) changes during ICA clamping. Material and Methods Between September 2012 and March 2014, 9 patients (10 sides) with carotid stenosis (70-99%) were surgically treated at our hospital. All CEAs were performed under general anesthesia, and we routinely used a carotid shunt with the intraoperative MEP monitors. When the MEP amplitude decreased to < 50% of the control during carotid clamping, the MEP amplitude was defined as significantly reduced. Results The MEP amplitude significantly decreased in 2 of the 10 procedures (20%) during ICA clamping. The mean distal ICA pressure varied widely, ranging from 13 to 48 mm Hg. In seven cases with a mean distal ICA pressure > 20 mm Hg, there were no significant changes in the MEP during ICA clamping. However, there were three cases with a mean distal ICA pressure < 20 mm Hg, and the MEP amplitude significantly decreased in two of those three patients from 4 to 5 minutes after clamping. Conclusions The present study provides considerable information about a higher incidence of MEP amplitude deterioration in CEA patients with a mean distal ICA pressure < 20 mm Hg during ICA clamping.