Effects of low-dose esketamine on hypoxaemia during thoracoscopic non-tracheal intubation anaesthesia: protocol for a double-blind, randomised controlled trial

Introduction Non-tracheal intubation anaesthesia for thoracoscopic surgery is associated with intraoperative hypoxaemia. Esketamine has both sedative and analgesic effects, which can increase lung compliance, reduce airway resistance and relax the respiratory smooth muscles. This study will investigate the effectiveness of low-dose esketamine in reducing the incidence of intraoperative hypoxaemia and other adverse events in patients undergoing thoracoscopic surgery without intubation anaesthesia. Methods and analysis This randomised controlled trial will enrol patients scheduled for non-intubation video-assisted thoracoscopic surgery at Shandong Provincial Hospital Affiliated to Shandong First Medical University. Eligible participants will be randomly allocated in a 1:1 ratio to receive either the esketamine group or the normal saline (placebo) group. The primary outcomes are the incidence of hypoxaemia and the time to its onset, with hypoxaemia defined as an intraoperative pulse oximetry ≤90% lasting for at least 10 s. Secondary outcomes include the incidence of intraoperative hypercapnia (Partial pressure of carbon dioxide (PCO 2 ) ≥60 mm Hg); concentrations of interleukin (IL)-6 and IL-8 at the end of surgery; postoperative Visual Analogue Scale scores; time to recovery of spontaneous respiration after laryngeal mask placement; time to laryngeal mask removal (measured from the end of surgery); awakening time; incidence of bradycardia (heart rate 20% reduction in blood pressure from the baseline value); incidence of ≤24-hour postoperative nausea and vomiting and hoarseness; time to ambulation, drinking and eating postoperatively; incidence of pulmonary complications within 2 weeks postoperatively; and length of hospital stay. All analyses will be performed based on using a modified intention-to-treat population principle. Ethics and dissemination The study protocol has been reviewed and approved by the Ethics Committee of Shandong First Medical University Affiliated Provincial Hospital, with approval number SWYX 2025–714. The trial is also registered with the Chinese Clinical Trial Registry under the identifier ChiCTR2400094821. On completion, the study findings will be prepared for publication and submitted to a relevant peer-reviewed journal. Trial registration number ChiCTR2400094821.