Volatile anesthetics, such as sevoflurane and desflurane, are commonly used in patients undergoing cardiac surgeries including off-pump coronary artery bypass. However, the effect of volatile anesthetics on microcirculation in patients undergoing off-pump coronary artery bypass has not been well conducted.

This is a prospective randomized clinical trial investigating the effect of sevoflurane vs. desflurane on tissue microcirculation in patients undergoing off-pump coronary artery bypass surgery. Eligible patients are going to be randomized to receive sevoflurane or desflurane, as a maintenance anesthetic, during the surgery. Tissue oxygen saturation and microcirculatory changes, such as an occlusion and recovery slope, during vascular occlusion test will be recorded during the surgery. The primary end point of the study is the difference in tissue oxygen saturation between the groups.

Inclusion Criteria:

• scheduled for off-pump coronary artery bypass surgery

Exclusion Criteria:

• any deformity or vascular abnormalities on upper arms
• cannot receive sevoflurane or desflurane for any reason (muscular diseases, etc)
• uncontrolled diabetes
• peripheral vascular disease
• severe renal dysfunction (end-stage renal disease)
• refuse to enroll
• pregnant