Dexmedetomidine (DEX) is a Alpha-2 specific agonist, is a common ICU sedation medication. In brain tumor resection craniotomy, it is proven to be effective in improving postoperative hypertension and tachycardia, mitigates postoperative nausea and vomiting and relives postoperative pain. In addition, many animal experiments show that DEX inhibits the proapoptosis in the mitochondrial in vivo and therefore avoids neuronal injury. It is also reported to be neuroprotective to isoflurane-induced neurotoxicity and to improve cerebral focal ischemic region (penumbra). However, the neuroprotective effects were never investigated clinically in patients undergoing brain tumor resection surgery.

Inclusion Criteria:

• Patients undergoing elective craniotomy for supratentorial brain tumor resection or cerebral vascular surgery
• age between 20 to 80 yr

Exclusion Criteria:

• Fever, elevated white blood cell or C-reactive protein
• Impaired liver function, eg. AST or ALT >100; liver cirrhosis > Child B class
• Impaired renal function, cGFR< 60 ml/min/1.73 m2
• Cardiac dysfunction, such as heart failure > NYHA class II