Variations in Crowding and Ambulance Diversion in Nine Emergency Departments

Abstract Objectives: The primary study aim was to examine the variations in crowding when an emergencydepartment (ED) initiates ambulance diversion.Methods: This retrospective, multicenter study included nine geographically disparate EDs. Daily EDoperational variables were collected during a 12-month period (January 2009 to December 2009), includ-ing total number of ED visits, mean overall length of stay (LOS), number of ED beds, and hours onambulance diversion. The primary outcome variable was the ‘‘ED workload rate,’’ a surrogate markerfor daily ED crowding. It was calculated as the total number of daily ED visits multiplied by the overallmean LOS (in hours) and divided by the number of ED beds available for acute treatment in a given day.The primary predictor variables were ambulance diversion, as a dichotomous variable of whether or notan ED went on diversion at least once during a 24-hour period, diversion hour quintiles, and sites.Results: The annual ED census ranged from 43,000 to 101,000 patients. The percentage of days that anED went on diversion at least once varied from 4.9% to 86.6%. On days with ambulance diversion, themean ED workload rate varied from 17.1 to 62.1 patient LOS hours per ED bed among sites. The magni-tude of variation in ED workload rate was similar on days without ambulance diversion. Differences inED workload rate varied among sites, ranging from 1.0 to 6.0 patient LOS hours per ED bed. ED work-load rate was higher on average on diversion days compared to nondiversion days. The mean differencebetween diversion and nondiversion was statistically signiﬁcant for the majority of sites.Conclusions: There was marked variation in ED workload rates and whether or not ambulancediversion occurred during a 24-hour period. This variability in initiating ambulance diversion suggestsdifferent or inconsistently applied decision-making criteria for initiating diversion.ACADEMIC EMERGENCY MEDICINE 2011; 18:941–946 a 2011 by the Society for Academic EmergencyMedicinea 2011 by the Society for Academic Emergency Medicine ISSN 1069-6563doi: 10.1111/j.1553-2712.2011.01149.x PII ISSN 1069-6563583 941From the Center for Policy and Research in Emergency Medicine, Department of Emergency Medicine, Oregon Health andScience University (DAH, RF), Portland, OR; the Department of Emergency Medicine, George Washington University School ofMedicine, Department of Health Policy, George Washington School of Public Health (JP), Washington, DC; the Department ofBiomedical Informatics & Emergency Medicine, Vanderbilt University (DA), Nashville, TN; the Department of EmergencyMedicine, Mount Sinai School of Medicine (NG, UH), New York, NY; t he Department of Emergency Medicine, University of ColoradoDenver School of Medicine (AAG), Aurora, CO; the Department of Emergency Medicine, University of Missouri–Kansas City,Truman Medical Center (JH), Kansas City, MO; the Department of Emergency Medicine, University of Pennsylvania (JAH),Philadelphia, PA; Geriatric Research, Education and Clinical Center, James J. Peters VAMC (UH), Bronx, NY; the Department ofEmergency Medicine, University of Rochester (MK), Rochester, NY; the Department of Emergency Medicine, NorthwesternUniversity Feinberg School of Medicine (EP), Chicago, IL; the Department of Emergency Medicine, George WashingtonUniversity (MS), Washington, DC; and the Department of Public Health and Preventive Medicine, Oregon Health and ScienceUniversity (RF), Portland, OR.Received January 7, 2011; revision received February 14, 2011; accepted February 15, 2011.Presented at the American College of Emergency Physicians Scientiﬁc Assembly Research Forum, Las Vegas, NV, September 2010.Dr. Aronsky is a board member and shareholder of Apogee Informatics (Madison, AL) and ii4sm (Basel, Switzerland). The rest ofthe authors have no disclosures or conﬂicts of interest to declare.Supervising Editor: Lowell Gerson, PhD.Address for correspondence: Daniel A. Handel, MD, MPH; e-mail: handeld@ohsu.edu. Reprints will not be available.