Compare the efficacy and safety of closed-loop target controlled infusion of propofol or etomidate at general anesthesia in geriatric patients

Inclusion Criteria:

1. Written informed consent.
2. Scheduled for Endotracheal intubated and general anesthesia for general surgery patients.
3. Age 60-75 yrs.
4. American Society of Anesthesia (ASA) classification I-II.
5. Expected time of surgery is less than 3 hours. -

Exclusion Criteria:

1. Body mass index is more than 36kg/m2.
2. Systolic blood pressure≥180 mm Hg or <90 mm Hg，diastolic blood pressure≥110 mm Hg or < 60 mm Hg.
3. Serious cardiac,cerebral,liver,kidney,lung, endocrine disease or sepsis.
4. Long term used hormone or adrenal suppression.
5. Allergy to trial drug or other contraindication.
6. Difficult airway occurred before,or difficult airway possibly occurred and difficult to extubation.
7. Abuse of narcotic analgesia or suspected.
8. Neuromuscular diseases.
9. Mentally unstable or has a mental illness.
10. Malignant Hyperthermia.
11. Pregnant or breast-feeding women.
12. Attended other trial past 30 days. -