Trends of standardized mortality ratio and its correlation with admission patient volume in different intensive care units: A retrospective study from a 12-year multi-center quality improvement project in a metropolitan area

Abstract

Background: Healthcare quality impacts patient prognosis in the intensive care unit (ICU). The healthcare quality can be indicated by the standardized mortality ratio (SMR) and is influenced by the volume of admitted patients. However, the correlation between the admission patient volume and SMR in ICUs remains unclear. Objective: This study examined SMR trends and their influencing factors and assessed the correlation between SMR and the admission patient volume across various ICU types. Methods: We analyzed data retrospectively gathered from 75 ICUs from a Quality Improvement Project from January 2011 to December 2022. It examined the correlations between SMR, admission patient volume, and other quality control indicators. We further compared SMR trends between two groups of ICUs with high or low admission volumes. The study also evaluated inter- and intra-group SMR disparities across hospital levels (secondary versus tertiary) and ICU types (general versus specialty). Results: The study encompassed 425,534 patients. A significant decline in SMR (P<0.001) was observed over the 12 years, alongside a notable negative correlation between admission patient volume and SMR (P<0.001). The low-admission group had a higher SMR than the high-admission group (P=0.010). Both the low (P=0.004) and high admission groups (P=0.001) showed a significant decreasing trend in SMR, with no significant inter-group difference (P=0.267). Moreover, the study identified distinct SMR trends between general ICUs (P=0.018) and secondary hospital ICUs (P=0.048) but not between specialtyICUs (P=0.511) and tertiary hospital ICUs (P=0.276). Conclusion: Over the past 12 years, SMR has significantly decreased. An inverse association was identified between ICU admission patient volume and SMR, with SMR exhibiting considerable variation across different ICU types. These findings underscore the importance of targeted management and healthcare quality enhancement strategies tailored to specific ICU settings.