The prone position is a special position often used for spinal surgery. As a special position of general anesthesia, after induction of general anesthesia, severe hemodynamic fluctuations often occur when the supine position is changed to the prone position, which seriously affects the patient's circulatory and respiratory functions.

Inclusion Criteria:

1. Prone spine surgery after general anesthesia is planned.
2. Age 18~85 years old.
3. ASA grade I or II.
4. BMI18.3-30kg/m2

Exclusion Criteria:

1. Unstable angina or myocardial infarction, coronary heart disease, congestive heart failure, structural heart disease, arrhythmia within 6 months;
2. Increased intracranial pressure and central nervous system injury or disease;
3. Severe hypertension
4. Patients with other diseases affecting their own circulatory system.
5. Have or have a history of severe mental disorders;
6. Bleeding volume >600ml or intraoperative blood transfusion treatment.
7. Severe liver and kidney insufficiency