The current study is designed to investigate the difference of plasma orexin A levels between Dexmedetomidine group and controlled group at emergence time from total intravenous anesthesia who will undergo elective lumbar surgery.

DESIGNING: Fifty-one patients with ASA physical status I or II scheduled for elective surgery under general anesthesia (lasting for 2h to 4h) were enrolled. Anesthesia was induced with propofol 1-2mg/kg and sufentanyl 0.2-0.3μg/kg. Following muscle relaxation with iv cisatracurium besylate 0.2mg/kg endotracheal intubation was performed. Anesthesia was maintained with target controlled infusion propofol (targeted concentration:2-5ug/ml ) and remifentanil (targeted concentration: 2-6ng/ml ). Muscle relaxation was maintained with intermittent, but it do not injected in 1h before surgery completion. Propofol and remifentanil were titrated to maintain the bispectral index (BIS) between 40 and 60 during anesthesia. The end-tidal carbon dioxide level was maintained between 30 and 40 mmHg by controlled mechanical ventilation. When the surgery was completed the investigators adjust the targeted concentration of propofol 2ug/ml and targeted concentration of remifentanil to 2ng/ml then stop all anesthetics. Dexmedetomidine group target controlled infusion dexmedetomidine (induction dose 1ug/kg with 10min, maintain dose 0.4ug/kg/h until 30min before surgery completion). Control group infusion same saline. Record time from stopping anesthetics to emergence and total doses of anesthetics. Arterial blood (2.5ml) was collected at the following time, such as before and 1h after induction of anesthesia, at emergence (1 min after tracheal extubation) and half an hour after tracheal extubation. 2.0ml Arterial blood was centrifuged at 3000 rpm for 15min at -4 ◦C in order to separate plasma then stored at -80 ◦C until assay for orexin A concentrations. 0.5ml Arterial blood was measured blood glucose.

Inclusion Criteria:

1. Participant is Adult (≥18 years old and ≤60 years old)
2. Participants with a Body Mass Index (BMI) 20-25 kg/m2
3. Participants with ASA physical status Ⅰor Ⅱ
4. Participants with Heart function rating Ⅰor Ⅱ
5. Patients will undergo elective surgery and general anesthesia
6. The operation time is 2h to 4h.

Exclusion Criteria:

1. Participant is a pregnant woman or a nursing mother.
2. Participants have a history of narcotics allergic reactions.
3. Indices of liver or kidney function is twice higher than normal.
4. Participants have a history or diagnosis of depression.
5. Participants have a history of Brain Trauma.
6. Participants have a history of narcotics addiction or drug addiction.
7. Participants or his family have an International Classification of Sleep
8. Disorders diagnosis of obstructive sleep apnea syndrome.
9. Patients are refuse this trail or are not able to sign informed consent.