Outcomes and cost-effectiveness of intermediate care units for patients discharged from the intensive care unit: a nationwide retrospective observational study

Background: The clinical and economic impacts of intermediate care units (IMCUs) on intensive care unit (ICU)-discharged patients remain unclear due to inconsistent outcomes in previous studies. Under Japan’s National Health Insurance Scheme, ICUs are categorized by staffing intensity (high or low). Using a nationwide inpatient database in Japan, we evaluated the clinical outcomes and cost-effectiveness of IMCUs for ICU-discharged patients. Methods: This retrospective observational study used a Japanese administrative database to identify patients admitted to the high-intensity ICU in hospitals with IMCUs between April 2020 and March 2023. Patients were categorized into the IMCU (IMCU group) and general ward (non-IMCU) groups. Propensity scores were estimated using a logistic regression model incorporating 14 variables, including patient demographics, and treatments received during ICU stay. One-to-one propensity score matching balanced baseline characteristics of each group. Clinical outcomes were compared between both groups, including in-hospital mortality, ICU readmission, length of ICU stay, length of hospital stay, and total medical costs. Surgical status and surgical area (e.g., cardiovascular) were considered in subgroup analyses. Data analyses were conducted using the chi-square test for categorical variables and t-test for continuous variables. Results: Overall, 162,243 eligible patients were categorized into the IMCU (n = 21,548) and non-IMCU (n = 140,695) groups. Propensity score matching generated 18,220 pairs. The IMCU group had lower in-hospital mortality and ICU readmission rates than the non-IMCU group. However, total costs were higher in the IMCU group. Subgroup analyses revealed the IMCU group had significantly lower mortality and lower total costs than the non-IMCU group in the cardiovascular [open thoracotomy] surgery subgroup. Conclusions: Discharge to an IMCU is associated with lower in-hospital mortality and ICU readmission rates compared to general ward discharge. High-risk subgroups, such as cardiovascular surgery patients, experienced cost-effective benefits from IMCU care. These findings highlight an association between IMCU admission and improved patient outcomes, suggesting a potential role in optimizing resource use in intensive care. Given the likelihood of selection bias in admission allocation, these findings should be interpretation with caution.