Effect of anesthesia induction with butorphanol on postoperative nausea and vomiting: A randomized controlled trial.

"Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article."

"The present study was approved by the Ethics Committee of the First Affiliated Hospital of Dalian Medical University (PJ-KS-KY-2020-161 [X]), and registered in the China Clinical Trial Center (ChiCTR2100045860). Patients ≥ 65 years old, who underwent gastrointestinal laparoscopic surgery from February 2020 to February 2021, were enrolled for the present study. Using the computer statistics software, these patients were randomly allocated into two groups in a 1:1 ratio: Sufentanil and butorphanol groups. Clinical trial registration statement: The study is registered in the China Clinical Trial Center (ChiCTR2100045860, 25/04/2021)."