Inclusion Criteria:  age ≥65 years and ≤90 years; scheduled to undergo surgery for spinal, under general anaesthesia; American Society of Anesthesiology (ASA) I-III; agree to participate, and give signed written informed consents.  Exclusion Criteria:  family history or history of malignant hyperthermia; History of propofol or sevoflurane allergy; demonstrated cognitive impairment on the modified Mini-Mental State Examination (score, <24of 30 or <20 of 30 if the patient's education year was less than 6 years or<17 if the patient is Illiterate); planned postoperative intubation or transferred to ICU; severe visual or auditory handicap; prior diagnoses of neurologic diseases or mental disorders (e.g., stroke, Parkinson's disease, dementia, schizophrenia, or depressive illness) take anticholinergic drugs or other drugs acting on the central nervous system for a long time before operation participating in other clinical studies in recent 3 months