Postoperative delirium in older adults is a common and costly complication after surgery. Propofol and sevoflurane are commonly used anesthetics to maintain sedation during spine surgery, and have different sedative and anti-inflammatory effects. The aim of this trial will be compare the impact of propofol versus sevoflurane on incidence of postoperative delirium in elderly patients after spine surgery.

Spine surgery is the third most common surgical procedure in older patients. With the increasing number of older patients undergoing spinal surgery, the risk of delirium after spinal surgery is currently expected to increase. The pathophysiological mechanisms of delirium remain poorly understood, leading models include neurotransmitter imbalance and neuroinflammation. Among precipitating factors, drugs (especially sedative hypnotic agents and anticholinergic agents), surgery, anesthesia, high pain levels, anemia, infections, acute illness, and acute exacerbation of chronic illness are the most commonly reported. Propofol and sevoflurane are commonly used anesthetics to maintain sedation during spinal surgery, and induce unconsciousness through different mechanisms. Meanwhile, previous studies have found that propofol and sevoflurane have different anti-inflammatory effects. Given their different sedative and anti-inflammatory effects, propofol and sevoflurane may have different effects on postoperative delirium. There are many studies to explore the effects of propofol and sevoflurane on postoperative delirium, but the conclusions are controversial. Therefore, a randomized, controlled, double-blind clinical study was designed to compare the impact of propofol and sevoflurane on delirium after spine surgery in elderly patients.

Inclusion Criteria:

1. age ≥65 years and ≤90 years;
2. scheduled to undergo surgery for spinal, under general anaesthesia;
3. American Society of Anesthesiology (ASA) I-III;
4. agree to participate, and give signed written informed consents.

Exclusion Criteria:

1. family history or history of malignant hyperthermia;
2. History of propofol or sevoflurane allergy;
3. 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);
4. planned postoperative intubation or transferred to ICU;
5. severe visual or auditory handicap;
6. prior diagnoses of neurologic diseases or mental disorders (e.g., stroke, Parkinson's disease, dementia, schizophrenia, or depressive illness)
7. take anticholinergic drugs or other drugs acting on the central nervous system for a long time before operation
8. participating in other clinical studies in recent 3 months