quantitative consciousness index monitoring of sedation during endoscopy：a prospective observational preliminary study

Background: The assessment of sedation depth during painless gastrointestinal endoscopy primarily relies on clinical experience due to the lack of a universally accepted objective standard. This study aimed to investigate the application of novel electroencephalography-derived indices, the quantitative consciousness index (qCON) and the quantitative nociception index (qNOX), for monitoring sedation and analgesia, and to determine the optimal qCON range associated with stable procedural conditions. Methods: This prospective observational preliminary study enrolled 220 patients undergoing elective gastroscopy or colonoscopy. All patients received propofol and sufentanil for anesthesia. Depth of anesthesia and nociception were continuously monitored using qCON and qNOX. Hemodynamic parameters, body movements, and cough reflexes were recorded at predefined time points. The primary outcome was optimal sedation quality, defined as hemodynamic fluctuations within 10% of baseline and the absence of body movement or coughing. Results: The optimal qCON range associated with stable hemodynamics and absence of noxious responses was 55～63 (95% CI: 55.25–62.62 for gastroscopy; 55.25–62.52 for colonoscopy). Strong correlations were observed between qCON and qNOX (gastroscopy: qNOX = 0.78 × qCON + 26.1, R² = 0.714; colonoscopy: qNOX = 0.83 × qCON + 22.47, R² = 0.716; p < 0.001). The qNOX index demonstrated a faster response to noxious stimuli compared to qCON during both induction and recovery phases. Conclusion: The qCON index provides an objective guidance for sedation depth during painless gastrointestinal endoscopy. Maintaining qCON within the range of 55 to 63 is associated with optimal procedural conditions. The combined use of qCON and qNOX monitoring can help optimize the balance between sedation and analgesia, potentially improving the safety and quality of endoscopic sedation. Trial registration Trial registration: This study was registered at ClinicalTrials.gov (Registration Number: NCT06604156). The registration was completed on April 11, 2024.