Rapid response system and mortality in intensive care unit: a nationwide cohort study in South Korea

The beneficial effects of a rapid response system (RRS) on clinical outcomes in patients admitted to a ward have been established. However, the relationship between RRS implementation and clinical outcomes in patients in the intensive care unit (ICU) has not yet been established. Therefore, we aimed to investigate whether the RRS affects clinical outcomes in critically ill patients admitted to the ICU. As a nationwide, population-based cohort study, all adult patients who were admitted to the ICU from 1 January 2019 to 31 December 2021 in South Korea were included. Patients in hospitals with an RRS formed the RRS group; those in hospitals lacking an RRS constituted the non-RRS group. In total, 900,606 patients admitted to the ICU were included in the final analysis. Among them, 365,305 (40.6%) were assigned to the RRS group, and 535,301 (59.4%) were assigned to the non-RRS group. After propensity score (PS) matching, a total of 454,748 patients (227,374 in each group) were included in the final analysis. In the PS-matched cohort, the RRS group showed 8% (odds ratio [OR]: 0.92, 95% confidence interval [CI]: 0.91, 0.94; P < 0.001) and 11% (hazard ratio: 0.89, 95% CI: 0.88, 0.90; P < 0.001) lower in-hospital mortality rates and 1-year all-cause mortality rates than the non-RRS group, respectively. In addition, ICU readmission rates and the occurrence rate for adverse events during hospitalization in the RRS group were 3% (OR: 0.97, 95% CI: 0.95, 0.98; P < 0.001) and 21% (OR: 0.79, 95% CI: 0.78, 0.80; P < 0.001) lower than those in the non-RRS group, respectively. RRS deployment was linked to lower in-hospital and 1-year all-cause mortality rates, ICU readmission rates, and the occurrence of adverse events during hospitalization among ICU patients. The findings indicate that using the RRS could assist not only patients in the ward but also critically ill patients in the ICU.