Clinical characteristics and risk factors for intensive care unit admission and mortality in rapid response team-activated ward patients: a retrospective cohort study at a tertiary hospital in South Korea

Background: Factors driving intensive care unit (ICU) transfer decisions and mortality after rapid response team (RRT) activation remain unclear. We identified independent predictors of ICU admission, 28-day mortality, and in-hospital mortality in RRT-activated ward patients. Methods: This retrospective cohort study included adults with first RRT activation from September 2023 to August 2025 at a Korean tertiary hospital (n=549). Multivariable logistic regression with backward elimination was used. Results: Of 549 patients, 191 (34.8%) were transferred to the ICU. ICU admission was independently predicted by procalcitonin >0.5 ng/ml (adjusted odds ratio [aOR], 2.833; P=0.021) and lower hemoglobin (aOR, 0.808 per g/dl; P=0.040), whereas solid tumor was associated with lower transfer likelihood (aOR, 0.142; P<0.001). Mortality did not differ significantly between ICU and ward groups at 28 days (27.7% vs. 27.7%, P=0.937) or during hospitalization (46.1% vs. 40.2%, P=0.162). Declining peripheral oxygen saturation (SpO₂)/fraction of inspired oxygen (FiO₂) ratio, rising lactate, and hyperkalemia predicted both mortality outcomes. Lower platelet count uniquely predicted 28-day mortality, whereas solid tumor, chronic kidney disease, and deep learning-based continuous cardiac arrest risk score (DeepCARS) additionally predicted in-hospital mortality. ICU admission itself was not independently associated with mortality. Conclusions: ICU transfer after RRT activation appears to reflect acute reversibility, clinical trajectory, and possible at/after-activation goals-of-care processes rather than severity alone. Mortality was more closely associated with oxygenation failure, hypoperfusion, and electrolyte instability than with disposition.