Effects of Sufentanil on the Intraoperative Hemodynamics

Inclusion Criteria: * Patients who undergo elective extracranial-intracranial bypass surgery * American Society of Anesthesiologists grade 1,2,3 * Age \> 18 years old Exclusion Criteria: * Refuse to participate to the study * American Society of Anesthesiologists grade 4 * Body Mass Index \< 18.5 kg/m2 or \> 35 kg/m2 * Allergic history of opioid * pregnant * MAO Inhibitor user * Severe respiratory insufficiency