Internal and Emergency Medicine

, Volume 7, Issue 2, pp 173–180 | Cite as

Emergency department crowding and risk of preventable medical errors

  • Stephen K. EpsteinEmail author
  • David S. Huckins
  • Shan W. Liu
  • Daniel J. Pallin
  • Ashley F. Sullivan
  • Robert I. Lipton
  • Carlos A. CamargoJr.


The objective of the study is to determine the association between emergency department (ED) crowding and preventable medical errors (PME). This was a retrospective cohort study of 533 ED patients enrolled in the National ED Safety Study (NEDSS) in four Massachusetts EDs. Individual patients’ average exposure to ED crowding during their ED visit was compared with the occurrence of a PME (yes/no) for the three diagnostic categories in NEDSS: acute myocardial infarction, asthma exacerbation, and dislocation requiring procedural sedation. To accommodate site-to-site differences in available administrative data, ED crowding was measured using one of three previously validated crowding metrics (ED Work Index, ED Workscore, and ED Occupancy). At each site, the continuous measure was placed into site-specific quartiles, and these quartiles then were combined across sites. We found that 46 (8.6%; 95% confidence interval, 6.4–11.3%) of the 533 patients experienced a PME. For those seen during higher levels of ED crowding (quartile 4 vs. quartile 1), the occurrence of PMEs was more than twofold higher, both on unadjusted analysis and adjusting for two potential confounders (diagnosis, site). The association appeared non-linear, with most PMEs occurring at the highest crowding level. We identified a direct association between high levels of ED crowding and risk of preventable medical errors. Further study is needed to determine the generalizability of these results. Should such research confirm our findings, we would suggest that mitigating ED crowding may reduce the occurrence of preventable medical errors.


Emergency services Crowding Medical errors 



We gratefully acknowledge the contribution of Dr. David Blumenthal to the NEDSS study that made this work possible, and of Dr. Sharolyn Medina, Director of Clinical Informatics, Picis, Inc. for her assistance with data extraction. We gratefully acknowledge the support of the Riggs Family/Emergency Medicine Foundation Health Policy Grant (Dallas, TX). The National ED Safety Study was supported by grant 5 R01 HS013099 from the Agency for Healthcare Research and Quality (Rockville, MD).

Conflict of interest



  1. 1.
    Bernstein SL, Aronsky D, Duseja R et al (2009) The effect of emergency department crowding on clinically oriented outcomes. Acad Emerg Med 16:1–10PubMedCrossRefGoogle Scholar
  2. 2.
    Sills MR, Fairclough D, Ranade D et al (2011) Emergency department crowding is associated with decreased quality of care for children with acute asthma. Ann Emerg Med 57:191–200PubMedCrossRefGoogle Scholar
  3. 3.
    Pitts SR, Niska RW, Xu J et al (2008) National Hospital Ambulatory Medical Care Survey: 2006 Emergency Department Summary. National Center for Health Statistics, Hyattsville, MDGoogle Scholar
  4. 4.
    Pines JM, Hollander JE (2008) Emergency department crowding is associated with poor care for patients with severe pain. Ann Emerg Med 51:1–5PubMedCrossRefGoogle Scholar
  5. 5.
    Hwang U, Richardson L, Livote E et al (2008) Emergency department crowding and decreased quality of pain care. Acad Emerg Med 15:1248–1255PubMedCrossRefGoogle Scholar
  6. 6.
    Fee C, Weber EJ, Maak CA et al (2007) Effect of emergency department crowding on time to antibiotics in patients admitted with community-acquired pneumonia. Ann Emerg Med 50:501–509, 509.e1Google Scholar
  7. 7.
    Pines JM, Localio AR, Hollander JE (2007) The impact of emergency department crowding measures on time to antibiotics for patients with community-acquired pneumonia. Ann Emerg Med 50:510–516PubMedCrossRefGoogle Scholar
  8. 8.
    Pines JM, Prabhu A, Hilton JA et al (2010) The effect of emergency department crowding on length of stay and medication treatment times in discharged patients with acute asthma. Acad Emerg Med 17:834–839PubMedCrossRefGoogle Scholar
  9. 9.
    Kulstad EB, Hart KM, Waghchoure S (2010) Occupancy rates and emergency department work index scores correlate with leaving without being seen. West J Emerg Med 11:324–328PubMedGoogle Scholar
  10. 10.
    Chalfin DB, Trzeciak S, Likourezos A et al (2007) Impact of delayed transfer of critically ill patients from the emergency department to the intensive care unit. Crit Care Med 35:1477–1483PubMedCrossRefGoogle Scholar
  11. 11.
    Sprivulis PC, Da Silva J, Jacobs IG et al (2006) The association between hospital overcrowding and mortality among patients admitted via Western Australian emergency departments. Med J Aust 184:208–212PubMedGoogle Scholar
  12. 12.
    Richardson DB (2006) Increase in patient mortality at 10 days associated with emergency department overcrowding. Med J Aust 184:213–216PubMedGoogle Scholar
  13. 13.
    Pines JM, Pollack CV, Diercks DB et al (2009) The association between emergency department crowding and adverse cardiovascular outcomes in patients with chest pain. Acad Emerg Med 16:617–625PubMedCrossRefGoogle Scholar
  14. 14.
    Liu SW, Thomas SH, Gordon JA et al (2009) A pilot study examining undesirable events among emergency department-boarded patients awaiting inpatient beds. Ann Emerg Med 54:381–385PubMedCrossRefGoogle Scholar
  15. 15.
    Vincent C, Simon R, Sutcliffe K et al (2000) Errors conference: executive summary. Acad Emerg Med 7:1180–1182PubMedCrossRefGoogle Scholar
  16. 16.
    White AA, Wright SW, Blanco R et al (2004) Cause-and-effect analysis of risk management files to assess patient care in the emergency department. Acad Emerg Med 11:1035–1041PubMedCrossRefGoogle Scholar
  17. 17.
    Friedman SM, Provan D, Moore S et al (2008) Errors, near misses and adverse events in the emergency department: what can patients tell us? CJEM 10:421–427PubMedGoogle Scholar
  18. 18.
    Sullivan AF, Camargo CA Jr, Cleary PD et al (2007) The National Emergency Department Safety Study: study rationale and design. Acad Emerg Med 14:1182–1189PubMedCrossRefGoogle Scholar
  19. 19.
    Ryan TJ, Antman EM, Brooks NH et al (1999) 1999 update: ACC/AHA guidelines for the management of patients with acute myocardial infarction: executive summary and recommendations. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Management of Acute Myocardial Infarction). Circulation 100:1016–1030PubMedGoogle Scholar
  20. 20.
    National Heart Lung and Blood Institute (1997) National Asthma Education and Prevention Program Expert Panel Report 2: guidelines for the diagnosis and management of asthma. National Heart, Lung, and Blood Institute, Bethesda, MDGoogle Scholar
  21. 21.
    American Society of Anesthesiologists Task Force on Sedation and Analgesia by Non-Anesthesiologists (2002) Practice guidelines for sedation and analgesia by non-anesthesiologists. Anesthesiology 96:1004–1017CrossRefGoogle Scholar
  22. 22.
    Burstin HR, Conn A, Setnick G et al (1999) Benchmarking and quality improvement: the Harvard Emergency Department Quality Study. Am J Med 107:437–439PubMedCrossRefGoogle Scholar
  23. 23.
    Saketkhou BB, Conet FJ, Noris M et al (1997) Emergency department use of aspirin in patients with possible acute myocardial infarction. Ann Intern Med 127:126–129PubMedGoogle Scholar
  24. 24.
    Magid DJ, Calonge BN, Rumsfeld JS et al (2000) Relation between hospital primary angioplasty volume and mortality for patients with acute MI treated with primary angioplasty vs thrombolytic therapy. JAMA 284:131–138CrossRefGoogle Scholar
  25. 25.
    Pope JH, Aufderheide TP, Ruthazer R et al (2000) Missed diagnoses of acute cardiac ischemia in the emergency department. N Engl J Med 342:1163–1170PubMedCrossRefGoogle Scholar
  26. 26.
    Mehta RH, Eagle KA (2000) Missed diagnoses of acute coronary syndromes in the emergency room—continuing challenges. N Engl J Med 342:1207–1210PubMedCrossRefGoogle Scholar
  27. 27.
    Gurwitz JH, Gore JM, Goldberg RJ et al (1998) Risk for intracranial hemorrhage after tissue plasminogen activator treatment for acute myocardial infarction. Ann Intern Med 129:597–604PubMedGoogle Scholar
  28. 28.
    Emond SD, Woodruff PG, Lee EY et al (1999) Effect of an emergency department asthma program on acute asthma care. Ann Emerg Med 34:321–325PubMedCrossRefGoogle Scholar
  29. 29.
    Bernstein SL, Verghese V, Leung W et al (2003) Development and validation of a new index to measure emergency department crowding. Acad Emerg Med 10:938–942PubMedCrossRefGoogle Scholar
  30. 30.
    Epstein SK, Tian L (2006) Development of an emergency department work score to predict ambulance diversion. Acad Emerg Med 13:421–426PubMedCrossRefGoogle Scholar
  31. 31.
    Hoot NR, Zhou C, Jones I et al (2007) Measuring and forecasting emergency department crowding in real time. Ann Emerg Med 49:747–755PubMedCrossRefGoogle Scholar
  32. 32.
    McCarthy ML, Aronsky D, Jones ID et al (2008) The emergency department occupancy rate: a simple measure of emergency department crowding? Ann Emerg Med 51:15–24PubMedCrossRefGoogle Scholar
  33. 33.
    Hoot NR, Zhou C, Jones I et al (2007) Measuring and forecasting emergency department crowding in real time. Ann Emerg Med 49:747–755PubMedCrossRefGoogle Scholar
  34. 34.
    Pines JM, McCarthy ML (2011) The crowding-effectiveness link: it doesn’t matter how fast we deliver care if we don’t deliver it right. Ann Emerg Med 57:201–202PubMedCrossRefGoogle Scholar
  35. 35.
    Croskerry P, Sinclair D (2001) Emergency medicine: a practice prone to error? CJEM 3:271–276PubMedGoogle Scholar
  36. 36.
    Kohn LT, Corrigan J, Donaldson MS, Institute of Medicine (U.S.) Committee on Quality of Health Care in America (2000) To err is human: building a safer health system. National Academy Press, Washington, DCGoogle Scholar
  37. 37.
    Rothschild JM, Churchill W, Erickson A et al (2010) Medication errors recovered by emergency department pharmacists. Ann Emerg Med 55:513–521PubMedCrossRefGoogle Scholar
  38. 38.
    Croskerry P, Shapiro M, Campbell S et al (2004) Profiles in patient safety: medication errors in the emergency department. Acad Emerg Med 11:289–299PubMedCrossRefGoogle Scholar
  39. 39.
    Campbell SG, Croskerry P, Bond WF (2007) Profiles in patient safety: a “perfect storm” in the emergency department. Acad Emerg Med 14:743–749PubMedGoogle Scholar

Copyright information

© SIMI 2011

Authors and Affiliations

  • Stephen K. Epstein
    • 1
    Email author
  • David S. Huckins
    • 2
  • Shan W. Liu
    • 3
  • Daniel J. Pallin
    • 4
  • Ashley F. Sullivan
    • 3
  • Robert I. Lipton
    • 1
    • 5
  • Carlos A. CamargoJr.
    • 3
  1. 1.Department of Emergency MedicineW/CC-2, Beth Israel Deaconess Medical CenterBostonUSA
  2. 2.Department of Emergency MedicineNewton-Wellesley HospitalNewtonUSA
  3. 3.Department of Emergency MedicineMassachusetts General HospitalBostonUSA
  4. 4.Department of Emergency MedicineBrigham and Women’s HospitalBostonUSA
  5. 5.Department of Emergency MedicineUniversity of Michigan Medical SchoolAnn ArborUSA

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