Outcome, Process, Utilization, and Cost Measurements of Patients Admitted to the ICU in Hospitals With Vs. Without an Intermediate Care Unit: A Nationwide Inpatient Database Study

Objective: To assess the impact of the presence of an intermediate care unit (IMCU) on ICU patient-level clinical outcomes as well as hospital-level utilization and cost measures by comparing those with vs without an IMCU, using Japan’s nationwide inpatient database. Design: Nationwide retrospective cohort study. Setting: Acute-care hospitals in Japan participating in the Diagnosis Procedure Combination Study Group database and Hospital Bed Function Reports from 2016 to 2022. Patients: A total of 2,278,521 adult patients admitted to the ICU between April 2016 and March 2023. Interventions: ICU admission to hospitals with vs without an IMCU. Measurements and Main Results: Outcomes included patient-level (in-hospital and ICU mortality, ICU readmission, and length of ICU stay) and hospital-year level (resource utilization and hospitalization costs) measures. Among the 2,278,521 eligible ICU patients from 557 hospitals across 2,953 hospital-years, 1,771,000 (77.7%) patients were admitted to hospitals with both an ICU and IMCU. Overall, 14.3% of patients were transferred between the ICU and IMCU, with large variability between hospitals. When estimating participant-average treatment effect for patient-level outcomes, ICU patients in IMCU-equipped hospitals had lower in-hospital mortality (adjusted odds ratio [aOR] 0.94; 95% CI, 0.89–0.99), ICU mortality (aOR 0.87; 0.83–0.92), fewer ICU readmissions (aOR 0.92; 95% CI, 0.85–1.00), and shorter ICU stays (adjusted rate ratio 0.98; 95% CI, 0.98–0.99). When estimating cluster-average treatment effect for hospital-level outcomes, IMCU-equipped hospitals had higher ICU bed occupancy (mean difference: 5.5%, 95% CI, 3.3–7.7%), higher occupancy for life-sustaining therapies (8.6%, 95% CI, 7.7–9.5%), increased reimbursement rates (5.4%, 95% CI, 4.0–6.8%), and increased annual revenue per ICU bed (25 million JPY, 19–31 million JPY). Conclusions: The presence of an IMCU in ICU-equipped hospitals was associated with improved patient outcomes and more efficient ICU utilization, with only modest increase in hospitalization costs. These findings support integration of the IMCU into critical care systems.