Ethics
The protocol of the current study was approved by the department of anesthesiology in the Second Affiliated Hospital of Xi’an Jiaotong University. Approval for this study was provided by the medical ethics committee (China). Written informed consent was obtained from all enrolled patients. The trial was registered with the medical ethics committee of the Second Affiliated Hospital of Xi’an Jiaotong University (the code of ethics: 2,020,138). This trial was registered by Anqi Feng with the Chinese Clinical Trial Registry on April 20, 2021 (number ChiCTR2100045671). Patients were screened for eligibility from December 2020 to December 2021. A total of 180 patients scheduled for elective major abdominal surgery were enrolled in this prospective study.