The Impact of Opening a Medical Step-Down Unit on Medically Critically Ill Patient Outcomes and Throughput: A Difference-in-Differences Analysis.

ABSTRACT

OBJECTIVE: To understand the impact of adding a medical step-down unit (SDU) on patient outcomes and throughput in a medical intensive care unit (ICU). DESIGN: Retrospective cohort study. SETTING: Two academic tertiary care hospitals within the same health-care system. PATIENTS Adults admitted to the medical ICU at either the control or intervention hospital from October 2013 to March 2014 (preintervention) and October 2014 to March 2015 (postintervention). INTERVENTIONS: Opening a 4-bed medical SDU at the intervention hospital on April 1, 2014. MEASUREMENTS AND MAIN RESULTS: Using standard summary statistics, we compared patients across hospitals. Using a difference-in-differences approach, we quantified the association of opening an SDU and outcomes (hospital mortality, hospital and ICU length of stay [LOS], and time to transfer to the ICU) after adjustment for secular trends in patient case-mix and patient-level covariates which might impact outcome. We analyzed 500 (245 pre- and 255 postintervention) patients in the intervention hospital and 678 (323 pre- and 355 postintervention) in the control hospital. Patients at the control hospital were younger (60.5-60.6 vs 64.0-65.4 years, P < .001) with a higher severity of acute illness at the time of evaluation for ICU admission (Sequential Organ Failure Assessment score 4.9-4.0 vs 3.9-3.9, P < .001). Using the difference-in-differences methodology, we identified no association of hospital mortality (odds ratio [95% confidence interval] 0.81 [0.42 to 1.55], P = .52) or hospital LOS (% change [95% confidence interval] -8.7% [-28.6% to 11.2%], P = .39) with admission to the intervention hospital after SDU opening. The ICU LOS overall was not associated with admission to the intervention hospital in the postintervention period (-23.7% [-47.9% to 0.5%], P = .06); ICU LOS among survivors was significantly reduced (-27.5% [-50.5% to -4.6%], P = .019). Time to transfer to ICU was also significantly reduced (-26.7% [-44.7% to -8.8%], P = .004). CONCLUSIONS: Opening our medical SDU improved medical ICU throughput but did not affect more patient-centered outcomes of hospital mortality and LOS.