Hemodynamic ischemic stroke during carotid endarterectomy: an appraisal of risk and cerebral protection.

Abstract

The purpose of this study was to validate the commonly accepted indicators of risk of ischemic stroke that indicate the necessity for cerebral protection during carotid endarterectomy (CEA), and to examine the efficacy of high-dose thiopentone sodium (thiopental) as a cerebral protection method in patients who are at high risk of intraoperative ischemic stroke. In a prospective study of 37 CEAs performed for symptomatic stenosis > 70%, functional and clinical indicators of risk of ischemic stroke during carotid cross-clamping were identified. Functional indicators of risk were the development of ischemic electro-encephalogram (EEG) changes and stump pressure < 25 mm Hg. Clinical indicators of risk were previous ischemic hemispheric stroke and severe bilateral disease. These indicators were correlated in all patients, some of whom had two or three coexisting indicators of risk. The EEG and stump pressure were monitored continuously during carotid occlusion in all operations. Carotid occlusion times were recorded. Intraluminal shunting was eliminated in favor of high-dose thiopental cerebral protection in all patients. Neurologic outcome was deemed to measure the efficacy of thiopental protection in patients who are identified to be at risk and, hence, in need of cerebral protection. The validity of the indicators used to identify risk of ischemic stroke during CEA was assessed. The absolute stroke risk was found to be 29.7% for the whole group (37 patients) and 57.9% in 19 patients who had commonly accepted indications for protective shunting. The correlation of ischemic EEG changes with stump pressure < 25 mm Hg was only 27.3%, whereas the expected correlation based on well-documented reports in the literature was 100%. The lack of correlation may have been related to the prevention of ischemic EEG changes by thiopental. There were no neurologic deficits in the series. The absence of neurologic deficit in the study indicated that thiopental protection was effective in preventing ischemic stroke in high-risk patients and safely replaced intraluminal shunting.