Association of emergency department crowding with inpatient outcomes

OBJECTIVE: To examine the association of higher emergency department (ED) census with inpatient outcomes on the day of discharge (inpatient length of stay, in-hospital mortality, ED revisits, and readmissions). DATA SOURCES AND STUDY SETTING: All-payer ED and inpatient discharge data and hospital characteristics data from all non-federal, general, and acute care hospitals in the state of California from October 1, 2015 to December 31, 2017. STUDY DESIGN: In retrospective data analysis, we examined whether ED census was associated with inpatient outcomes for all inpatients, including those not admitted through the ED. The main predictor variable was ED census on day of discharge, categorized based on hospital year and day of week. Separate linear regression models with robust SEs and hospital fixed effects examined the association of ED census on inpatient outcomes (length of stay, 3-day ED revisit, 30-day all-cause readmission, in-hospital mortality), controlling for patient and visit-level factors. We stratified analyses by whether admission was elective or unscheduled. EXTRACTION METHODS: Inpatient discharges in non-federal, general medical hospitals with EDs. PRINCIPAL FINDINGS: We examined 5,784,253 discharges. The adjusted model showed that, compared to when the ED was below the median, higher ED census on the day of discharge was associated with longer inpatient length of stay, lower readmissions, and higher in-hospital mortality (90th percentile for length of stay: +0.8% 95% confidence interval, CI: +0.6% to +1.1%; readmissions: -0.59 percentage points or -5.6% 95% CI: -0.0071 to -0.0048; mortality: +0.14 percentage points or +5.4% 95% CI: +0.0009 to +0.0018). Correction added on 18 November 2022, after first online publication: '[odds rato, OR -5.6%' and 'OR +5.4%' of the preceding sentence have been corrected to 'or -5.6%' and 'or +5.4%', respectively, in this version.] Results for length of stay were primarily driven by patients with elective admissions, while results for readmissions and in-hospital mortality were primarily driven by patients with unscheduled admissions. CONCLUSIONS: This study suggests that ED crowding may affect inpatients throughout the hospital, even patients who are already admitted to the hospital.