In-hospital mortality of patients admitted to the intermediate care unit in hospitals with and without an intensive care unit: a nationwide inpatient database study

Intermediate care units (IMCUs) provide care for patients who need more intensive treatment than general wards but less than intensive care units (ICUs). Although the concept of an IMCU requires co-location with an ICU, some hospitals have IMCUs but no ICUs, which potentially worsens patient outcomes. This study aimed to examine the annual trends and care processes, and compare the outcomes of patients admitted to IMCUs in hospitals with and without ICUs using a nationwide inpatient database in Japan. This retrospective cohort study was conducted from 2016 to 2022 using the Diagnosis Procedure Combination Database and Hospital Bed Function Reports in Japan. The main exposure was admission to the IMCU in hospitals with and without ICUs. The primary outcome was in-hospital mortality rate in hospitals with and without ICUs that were compared using multilevel logistic regression models adjusted for confounders. The number of IMCU beds in hospitals without ICUs increased by 59% from 3,388 in 2016 to 5,403 in 2022, and the IMCU beds in hospitals without ICUs represented 38% (n = 5,403/14,185) of all IMCU beds in Japan in 2022. Among the 3,061,960 eligible patients in the IMCUs, 2,296,939 (75%) and 765,021 (25%) were admitted to hospitals with and without ICUs, respectively. Transfer between IMCUs and ICUs occurred for 10.5% (n = 320,938/3,061,960) of patients, with a large variability between hospitals. After adjusting for potential confounders, patients admitted to IMCUs in hospitals without ICUs had significantly higher in-hospital mortality than those in hospitals with ICUs (adjusted odds ratio: 1.15; 95% confidence interval: 1.10–1.20; p < 0.001). Admission in IMCUs in hospitals without ICUs increased, but was associated with higher in-hospital mortality. These findings suggest that IMCUs should be placed in hospitals with ICUs.