This research is expected to study ultrasonic measurement of internal jugular vein and inferior vena cava, which can be used as a good index to predict hypotension after anesthesia induction, and its measurement method is simple and quick.

The induction of anesthesia is the process from the physiological state to the anesthetic state in a short period of time. Hypotension after anesthesia induction is closely related to many organ injuries. Gastrointestinal surgery patients' prohibition of fasting is an important mechanism of severe hypotension after anesthesia induction. At present, ultrasonic measurement of inferior vena cava and internal jugular vein has been proved to be a convenient and non-invasive means to evaluate patients' blood volume. The purpose of this research was to study the relativity between ultrasonic measurement of inferior vena cava and internal jugular vein and hypotension after anesthesia induction in patients.

Inclusion Criteria:

• Gastrointestinal surgery
• BMI 18~24
• ASA score gradeⅠ~ III

Exclusion Criteria:

• anemia
• cirrhosis
• Emergency surgery
• severe hypertension
• New York Heart Association III ~ IV or ejection fraction <40%
• cirrhosis
• Other serious systemic diseases

patients undergoing gastrointestinal surgery in the Affiliated Hospital of Xuzhou Medical University