Can frailty predict low oxygen during procedure sedation in older adults?

Intraoperative hypoxemia is a common and serious complication during monitored anesthesia care for elective endoscopic retrograde cholangiopancreatography (ERCP), especially in older adults. Frail patients have reduced physiologic reserve and are at increased risk of life-threatening events including unplanned intubation, hemodynamic collapse, and hypoxic brain injury. However, the independent relationship between frailty and intraoperative hypoxemia during sedated ERCP remains poorly defined, and no validated risk prediction model exists for this high-risk population. This single-center, dual-cohort study will be conducted at China-Japan Friendship Hospital to evaluate whether preoperative frailty can predict intraoperative hypoxemia in patients aged 65 years and older undergoing elective ERCP. Frailty will be assessed primarily using the Frailty Index (FI), with secondary screening by the Modified Frailty Index-11 (mFI-11), Edmonton Frail Scale (EFS), Clinical Frailty Scale (CFS), FRAIL scale, and Fried phenotype. The primary outcome is intraoperative hypoxemia, defined as SpO₂ \< 90% for 5 seconds or longer. In the retrospective phase (n = 313), investigators will identify risk factors and develop a preliminary prediction model. In the prospective phase (n = 388), the model will be validated, refined, and internally tested for discrimination, calibration, and clinical utility. This study aims to establish frailty as a reliable preoperative risk marker and provide a clinically practical prediction tool to support risk stratification, personalized sedation strategies, and perioperative safety in elderly patients undergoing ERCP.