Development and Validation of a Dynamic Nomogram for Predicting Postdischarge Nausea and Vomiting in Adults Undergoing Ambulatory Surgery: A Retrospective Cohort Study

AIMS: To develop and temporally validate a dynamic nomogram for predicting postdischarge nausea and vomiting (PDNV) in adults undergoing elective ambulatory surgery and to support team-based, nurse-coordinated discharge risk assessment. BACKGROUND: PDNV can impair recovery and increase unplanned healthcare use. Static risk scores do not incorporate intraoperative physiological changes or early postanaesthesia care unit (PACU) findings. DESIGN: A retrospective cohort study. METHODS: Adults aged 18 years or older undergoing elective ambulatory surgery between 2023 and 2025 were included. The outcome was nausea, vomiting, retching or rescue antiemetic use within 24 h after discharge. Penalized regression selected predictors from preoperative, intraoperative, PACU and discharge data, followed by logistic regression refitting and nomogram construction. Internal validation repeated imputation, tuning, selection and refitting in 1000 bootstrap samples. Performance was evaluated using discrimination, calibration, Brier score, expected-to-observed ratio, decision curve analysis and temporal validation. RESULTS: Nine predictors were retained. In the development cohort, the optimism-corrected C-index, calibration slope, Brier score and expected-to-observed ratio were 0.79, 0.91, 0.131 and 1.01, respectively. In the temporal validation cohort, the corresponding AUC, calibration slope, Brier score and expected-to-observed ratio were 0.77, 0.93, 0.139 and 1.05. The nomogram provided greater net benefit than the Apfel score across threshold probabilities of 10%-30%. CONCLUSION: The nomogram showed acceptable discrimination and generally preserved calibration. It may support team-based discharge assessment, but external validation, electronic workflow integration and prospective usability evaluation are required before routine implementation.