The investigators investigated in the present study whether selective head cooling and dexmedetomidine has an effect on cerebral oxygenation during liver transplantation and has cerebral protective effect in patients undergoing liver transplantation.

Inclusion Criteria:

• Scheduled for OLT, selected from the Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, China.
• Sign the informed consent

Exclusion Criteria:

• The patients with a history of neurological or psychiatric disorders which impair cognitive processes, including previously established de-mentia, stroke, schizophrenia and depression were excluded from the study.
• Patients diagnosed with hepatic encephalopathy or had a low Mini-Mental State Examination (MMSE) score (below 24) preoperatively.
• With concurrent diseases such as renal insufficiency, diabetes mellitus were also excluded.
• Patients were excluded if severe reperfusion syn-drome (mean arterial pressure below 60mmHg sustained over 15minutes) occurred perioperatively.