Health policy/original researchEffect of Emergency Department Crowding on Outcomes of Admitted Patients
Introduction
Emergency department (ED) crowding has become an international health delivery problem.1, 2, 3 Increasing frequency of ambulance diversion and left-without-being-seen visits have led the Institute of Medicine to describe US EDs as nearing “the breaking point,”1 and multiple other countries have experienced a surge of ED crowding during the past decade. National policy responses have varied from none to system-wide performance targets.2
Establishing a definitive relationship between ED crowding and subsequent mortality may motivate policymakers to address ED crowding as a top public health priority. Limitations of previous studies assessing the effect of ED crowding on admitted patients include small hospital samples (n=1 to 6),4, 5, 6, 7, 8 lack of case-mix adjustment for comorbidities and primary illness diagnosis,3, 4, 5, 6, 8 lack of adjustment for potential hospital-level confounders, and restriction to specific subgroups such as patients with acute myocardial infarction,9 trauma,10 pneumonia,11 or critical illness.12
To address these limitations, we studied the effect of ED crowding on patient outcomes in a regional cohort of adult patients admitted through an ED. ED crowding was represented by a hospital-normalized measure of ambulance diversion hours on the day of admission. We hypothesized that high ED crowding would be associated with increased inpatient mortality rates, length of stay, and hospital costs in a general population of hospitalized patients.
Section snippets
Study Design and Participants
We performed a retrospective cohort study of adult admissions through the EDs of nonfederal California hospitals for 2007. Hospital-level exclusion criteria were the absence of basic or comprehensive emergency services, facilities that closed their hospital or ED in 2007, and facilities that primarily served children (because ED crowding may have differential effects in pediatric compared with adult populations13). We excluded hospitals that were prohibited from diverting ambulances by local
Results
The Figure illustrates the construction of the study cohort. Excluded hospitals were more likely to be located in single-hospital, low-population-density counties and served patients who were more likely to be young, white, and poor than those treated at included hospitals (Table E1, available online at http://www.annemergmed.com). Our study cohort included 995,379 admissions occurring through the ED at 187 hospitals. Admission and hospital level characteristics are presented in Table 1 and
Limitations
Our study is subject to potential limitations. First, ambulance diversion hours may be an imperfect measure of ED crowding. For example, this measure may be poorly sensitive to ED crowding at facilities that rarely request ambulance diversion. Furthermore, daily diversion hours may not reflect ED crowding experienced by an individual patient, and variation in ED crowding may be greater within than across days.22 Unfortunately, the time of ED evaluation is unavailable through the Office of
Discussion
Patients admitted through the ED during periods of high ED crowding died more often than similar patients admitted to the same hospital when the ED was less crowded. There were also modest increases in inpatient length of stay and hospital costs. These findings persisted after extensive case-mix adjustment for patient demographics, comorbidities, and primary discharge diagnosis. Our fixed-effect model controls for confounding by facility characteristics, and our hospital-normalized definition
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Supervising editor: Brendan G. Carr, MD, MS
Author contributions: BCS, REW, DZ, and SMA designed the study. BCS obtained funding for this study. BCS and RYH were responsible for data collection. BCS supervised the overall data collection process, had full access to all the data in the study, and takes responsibility for the integrity of the data and the accuracy of the data analysis. WH and HM were responsible for data management and cleaning. REW and L-JL performed the data analysis. BCS and RYH drafted the article. All authors contributed substantially to article revisions and approved the final article for submission. BCS takes responsibility for the paper as a whole.
Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). This study was supported by an Emergency Medicine Foundation Health Policy grant and US federal grant R03 HS18098. Dr. Sun was supported by NIH/NIA grants K12 AG001004 and the UCLA Older Americans Independence Center, P30-AG028748. Dr. Hsia was supported by the NIH/NCRR/OD UCSF-CTSI grant KL2 RR024130 and the Robert Wood Johnson Foundation Physician Faculty Scholars. The contents do not represent the official views of the Emergency Medicine Foundation, the Agency for Healthcare Research and Quality, the National Institutes of Health, or the Robert Wood Johnson Foundation. The funding sponsors had no role in design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the article.
Please see page 606 for the Editor's Capsule Summary of this article.
Publication date: Available online December 6, 2012.