Compare the incidence of hypotension during the propofol-induced period between the internal jugular vein variability-guided fluid infusion group and the conventional fluid infusion group through a fluid infusion experiment before anesthesia induction, so as to evaluate the feasibility of using the internal jugular vein variability under deep inspiration to guide preoperative fluid infusion.

Ultrasound records at least one quiet breathing cycle and one deep inhalation cycle to calculate IJVV Propofol was infused target-controlled at 4 μg/ml, and changes in arterial blood pressure within 3 minutes of propofol induction were observed.

Plan to conduct a prospective randomized controlled study to compare the incidence of hypotension during the propofol-induced period between the internal jugular vein variability-guided fluid infusion group and the conventional fluid infusion group through a fluid infusion experiment before anesthesia induction.

Inclusion Criteria:

• age over 60 years； American Society of Anesthesiology (ASA) status Ⅱ-Ⅲ； Surgery with radial artery puncture； Propofol induction；

Exclusion Criteria:

• BMI≥30kg/m2； People with short necks； Previous hypotension (systolic blood pressure <90mmHg or mean arterial pressure<65mmHg)； Previous poorly controlled hypertension； Cardiac insufficiency , EF value<50%； Upper limb deep vein thrombosis； History of radiotherapy or neck surgery； Inability to maintain a supine position for necessary measurements； Mechanical ventilation status or inability to take deep breaths patients； gastrointestinal surgery； Patients allergic to propofol； Restricted fluid intake；

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