To investigate whether dexmedetomidine reduce liver injury after hepatectomy. During hepatectomy, surgeons always took inflow occlusion to reduce blood loss with Pringle maneuver. A few clinical studies had shown dexmedetomidine could reduce ischaemia/reperfusion (IR) injury caused by the secretion of reactive oxygen species and inflammatory cytokines. Glutathione-S-transferase (GST) was a sensitive and specific marker for hepatic injury in several studies before. So the investigator decided to use it as the primary endpoint. Besides, in our center, there are some liver resection surgeries that didn't need occlusion. So it can serve the best placebo for determine the the actual effect of dexmedetomidine on the IR injury in further subgroup analysis.

The purpose of our study is to compare liver injury with dexmedetomidine. The enrolled patients were randomized into two group. In the study group, dexmedetomidine, diluted in 0.9% sodium chloride with the concentration of 4 ug ml-1 is administered with an loading dose of 0.5ug kg-1 of 10 min, and maintained with infusion rate of 0.5 ug kg-1 h-1. While, 0.9% sodium chloride serves as the placebo with the same loading dose and infusion rate in the control group. The infusion is ceased after the resection of the hepatic issues.

GST is a sensitive and specific marker for hepatic injury in several studies before and is taken as the primary endpoint. And the investigator use other inflammatory cytokines reflecting the systemic inflammatory response in serum. Besides these, the investigator observe the hemodynamic changes during the operation time and complications related with anesthesia and surgery.

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) I~III
• selected to have hepatectomy in our hospital, Child-Pugh A
• patient's consent

Exclusion Criteria:

• refusing to attend or attending in other clinical study
• having severe cardio-pulmonary disease, ejection fraction (EF)<40%, having cardiac infarction in recent three months, chronic obstructive pulmonary disease (COPD) (PaO2<60mmHg)
• pregnant or lactating women
• having neuropsychiatric disorders
• emergent surgeries，hemorrhage shock，
• rupture and hemorrhage of liver tumor