This will be a prospective, randomized, double-blinded, cross-over clinical trial to compare the effects of phenylephrine or norepinephrine on cardiac function during carotid artery surgery in patients under general anesthesia. The effect of the vasopressor on cardiac function will be measured using electrocardiography, transesophageal echocardiography and cardiac troponin I intraoperatively and postoperatively. We will use a cross-over pattern since both drugs exhibit rapid onset and short duration of action. We hypothesize that there will be less myocardial ischemia associated with the use of norepinephrine when compared with phenylephrine during carotid artery surgery.

Inclusion Criteria:

• Elective carotid endarterectomy under general anesthesia
• > 18 years old
• Written informed consent

Exclusion Criteria:

• Contraindication to general anesthesia
• Contraindication to transesophageal anesthesia
• esophageal disease
• esophageal stricture
• history of esophageal or gastric bleeding
• esophageal anatomic abnormality
• past esophageal or gastric surgery
• severe dysphagia