Design and patients
postoperative pain
We performed a prospective, double-blind, up-down sequential allocation study to determine the ED50 of esketamine for preventing early postoperative pain. The study was conducted in agreement with the Helsinki Declaration and approved by the Ethics Committee of Affiliated Hospital of Nantong University. All participants underwent an informed consent process and signed a consent form. The study was registered in the Chinese Trial Registry (ChiCTR2200066663, 13/12/2022). This study adhered to the CONSORT 2010 statement.The patients who were scheduled to receive laparoscopic cholecystectomy were enrolled in the study. The inclusion criteria for the studies were as follows: (1) age: ≥18 years old, (2) BMI: 18–28 kg/m