Patient flow variability and unplanned readmissions to an intensive care unit*

OBJECTIVE: To determine whether high patient inflow volumes to an intensive care unit are associated with unplanned readmissions to the unit. DESIGN: Retrospective comparative analysis. SETTING: The setting is a large urban tertiary care academic medical center. PATIENTS: Patients (n = 3233) discharged from an adult neurosciences critical care unit to a lower level of care from January 1, 2006 through November 30, 2007. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The main outcome variable is unplanned patient readmission to the neurosciences critical care unit within 72 hrs of discharge to a lower level of care. The odds of one or more discharges becoming an unplanned readmission within 72 hrs were nearly two and a half times higher on days when > or =9 patients were admitted to the neurosciences critical care unit (odds ratio, 2.43; 95% confidence interval, 1.39-4.26) compared with days with < or =8 admissions. The odds of readmission were nearly five times higher on days when > or =10 patients were admitted (odds ratio, 4.99; 95% confidence interval, 2.45-10.17) compared with days with < or =9 admissions. Adjusting for patient complexity, the odds of an unplanned readmission were 2.34 times higher for patients discharged to a lower level of care on days with > or =10 admissions to the neurosciences critical care unit (odds ratio, 2.34; 95% confidence interval, 1.27-4.34) compared with similar patients discharged on days of < or =9 admissions. CONCLUSIONS: Days of high patient inflow volumes to the unit were associated significantly with subsequent unplanned readmissions to the unit. Furthermore, the data indicate a possible dose-response relationship between intensive care unit inflow and patient outcomes. Further research is needed to understand how to defend against this risk for readmission.