Comparison of the Effects of Trendelenburg Position and Passive Leg Lift on Hemodynamics in Abdominal Surgery Patients

How to maintain the stability of circulation during anesthesia has always been a concern of clinicians, including shorting the preoperative fasting time under the condition of full preoperative preparation, and giving appropriate amount of nutrient solution in combination with the patient's situation 2\~4 h before surgery to reduce the blood volume insufficiency of patients before general anesthesia induction, vasoactive drugs, etc. Among them, passive leg lifting experiment is widely recognized in the world. Although passive leg lifting has many advantages, it still has some limitations in the operation process. This study tried to find the corresponding head low and foot high Angle corresponding to the same hemodynamic changes caused by passive leg lifting.