Effects of Different Ventilation Modes on Airway Pressure and Intracranial Pressure in Patients in the Trendelenburg Position: a Randomized, Double-blind, Controlled Trial

2.1. Trial design This single-center, parallel-arm, double-blinded, randomized, noninferiority trial was performed at Inner Mongolia Baogang Hospital, The Third Affiliated Hospital of Inner Mongolia Medical University, China, from January 2022 to June 2024. The study adhered to Good Clinical Practice guidelines and the principles of the Declaration of Helsinki. 2.2. Participants This study enrolled patients aged 27-77 years who underwent elective laparoscopic myomectomy at our institution from February 2023 to August 2024. The patients had an ASA classification of I-III. Patients were excluded if they had an allergy to the anesthetic drugs used in the study, adverse effects to the analgesics included, liver cirrhosis or kidney dysfunction, or cardiopulmonary impairment. Patients were also excluded if they were uncooperative, defined as being unable to undergo clinical assessment. This study was approved by the Medical Ethics Committee of Inner Mongolia Baogang Hospital (2023-MER-106) .

2.3. Randomization and blinding Patients who met the inclusion criteria were randomly assigned to one of three groups (PCV, VCV, or PRVC) in a 1:1:1 ratio using a random number table. The anesthesiologists and surgeons performing the anesthesia and assisting with the surgery were only informed of the mechanical ventilation mode to be used. Patients were unaware of their group assignment because mechanical ventilation was initiated after anesthesia induction when they were unconscious. The anesthetic nurses and doctors evaluating the patients postoperatively were also unaware of the group assignments.

2.4. Anesthetic and analgesic managements Anesthesia was administered according to standardized institutional protocols. Patients received 1.5-2 mg/kg propofol, 1-2 mg/kg rocuronium, and 1-2 μg/kg remifentanil for induction. Anesthesia was maintained with inhaled sevoflurane or desflurane, with the inhaled concentration adjusted based on the electroencephalogram (EEG). Remifentanil was continuously infused at 0.05-0.2 μg/kg/min, adjusting blood pressure and heart rate to within ±20% of baseline values.

Thirty minutes before anesthesia emergence, all patients were administered 30 mg ketorolac tromethamine (Chengdu Dominant Pharmaceuticals Co., Ltd., China), 1 μg/kg fentanyl, and 4 mg tramadol (Jiangsu Hengrui Pharmaceuticals Co., Ltd., China), and a patient-controlled analgesia (PCA) device (Y-G-B3, JIANGSU YaGuang Medical Appliance CO., LTD., China) was initiated. The PCA was set to deliver a bolus dose of 15 μg fentanyl with a 10-minute lockout interval and no basal infusion (1 mg fentanyl and 8 mg tramadol mixed in 100 mL of normal saline solution). Data on PCA usage were collected, including the time and dose of each administration.

If the pain remained intolerable despite these measures, rescue analgesia was administered, including 1 μg/kg fentanyl or 30 mg ketorolac tromethamine IV.