Clinical Research Directory

Inclusion Criteria: 1. Elderly patients (≥ 65 years old）; 2. Patients with American Society of Anesthesiologists(ASA) grade I-III; 3. Patients scheduled to undergo elective non-cardiac surgery under general anesthesia, with an anticipated surgical duration of over 1 hour； 4. Patients with intra-tracheal intubation following intravenous general ；anesthesia induction and maintenance； Exclusion Criteria: 1. Patients with vascular diseases such as aortic aneurysm, aortic dissection, symptomatic atherosclerotic obliterans, Buerger's disease, and Raynaud's syndrome 2. Patients with secondary hypertension, including renal hypertension and endocrine hypertension. 3. Patients with chronic kidney disease requiring dietary restrictions or dialysis. 4. Patients with Parkinson's disease or other conditions causing tremors. 5. Patients with problems related to oral food ingestion or those requiring enteral nutrition. 6. Patients with difficulties in measuring the upper extremities or communication problems that would interfere with study procedures. 7. Patients unable to remain in a supine position for at least 2 hours.