 The purpose of this study is to compare the hemodynamics effects of two usual hypnotic agents LENOXe TM xenon 100 vv and sevoflurane during a general anesthesia for carotid endarterectomy in elderly patients. The hypothesis is that the use of the LENOXe TM xenon 100 vv allows to obtain per-operating hemodynamic stability non inferior than with sevoflurane. 