Archives of Academic Emergency Medicine. 2019; 7 (1): e52 REV I EW ART I C L E Outcomes of Crowding in Emergency Departments; a Sys- tematic Review Hamid Reza Rasouli1, Ali Aliakbar Esfahani2, Mohammad Nobakht2, Mohsen Eskandari2, Sardollah Mahmoodi1, Hassan Goodarzi1, Mohsen Abbasi Farajzadeh2∗ 1. Trauma Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran. 2. Marine Medicine Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran. Received: June 2019; Accepted: July 2019; Published online: 28 August 2019 Abstract: Introduction: Emergency Department (ED) crowding is a global public health phenomenon affecting access and quality of care. In this study, we seek to conduct a systematic review concerning the challenges and out- comes of ED crowding. Methods: This systematic review utilized original research articles published from 1st January 2007, to 1st January 2019. Relevant articles from the PubMed (MEDLINE), EMBASE, and Google scholar databases were extracted using predesigned keywords. Following the PRISMA guidelines, two reviewers inde- pendently evaluated the quality of the studies using Critical Appraisal Skills Programme for cohort studies and qualitative studies, and Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument for studies. Results: Out of the total of 73 articles in the final record, we excluded 15 of them because of poor quality. This systematic review synthesized the reports of 58 original articles. The outcomes of multiple indi- vidual patients and healthcare-related challenges are comprehensively assessed. Conclusions: ED crowding affects individual patients, healthcare systems and communities at large. The negative influences of crowding on healthcare service delivery result in delayed service delivery, poor quality care, and inefficiency; all negatively affecting the emergency patients’ healthcare outcomes, in turn. Keywords: Crowding; outcome assessment; emergency service, hospital; systematic review Cite this article as: Rasouli H R, Aliakbar Esfahani A, Nobakht M, Eskandari M, Mahmoodi S, Goodarzi H, Abbasi Farajzadeh M. Outcomes of Crowding in Emergency Departments; a Systematic Review. Arch Acad Emerg Mede. 2019; 7(1): e52. 1. Introduction The requirement of emergency healthcare service is an on- going issue (1). The emergency department (ED) is expected not only to provide emergency care to patients but also to ful- fill the needs of the providers, and the communities at large. Besides, the emergency department might be the only source of healthcare services to people especially in rural communi- ties (1, 2). Evidence shows an increase in emergency healthcare service utilization because of the increased rates of accidental in- juries. However, the capacity of the emergency healthcare systems has not been well developed to respond to such high demand because creating a balance between emergency ser- vices and the required resources is challenging, especially ∗Corresponding Author: Mohsen Abbasi Farajzadeh; Marine Medicine Re- search Center, Baqiyatallah University of Medical Sciences, Tehran, Iran. Tel: +9888053766, E-mail: mohsen10_fam@yahoo.com in under-resourced countries (3-5). This condition leads to crowding of the EDs, which in turn impose public health challenges related to quality of healthcare and outcomes. Crowding is a situation when an identified need for emer- gency healthcare services exceeds the available resources to provide emergency care to patients within an appropriate time frame (1, 3, 6). Crowding of the ED leads to adverse outcomes for the patients, providers, the healthcare system and the community. Delay in service provision to patients not only can compromise the quality of the emergency ser- vices but can also worsen their consequences. Crowding of the ED might also lead to the violations of the norms and the service provision standards, which in turn might result in patients leaving the facilities without getting the required services. Thus, this systematic review aims to describe the consequences of ED crowding for emergency patients, emer- gency care providers, and healthcare systems. The findings are anticipated to provide inputs to decision-makers for a better understanding of the effects of ED crowding and to contextualize practical solutions to improve the quality of This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem H R. Rasouli et al. 2 Figure 1: Study selection flowchart. medical emergency services. 2. Methods: 2.1. Search Strategy In this review, we adopted the definition for “crowding” from the American College of Emergency Physicians which states “Crowding occurs when the identified need for emer- gency services exceeds available resources for patient care in the emergency department, hospital, or both.” Then, we searched for articles related to crowding in EDs and its major outcomes published in English between January 1, 2007, and January 1, 2019, in PubMed (MEDLINE) and Embase elec- tronic databases. We applied search terms based on common keywords in the literature concerning the consequences of emergency department crowding (Table 1). We used suitable combinations of "OR" and "AND" in all databases. Also, we searched Google scholar and Google to find relevant papers. 2.2. Data collection and quality assessment Two reviewers (HR.R. & A.AE.), independently screened the titles, abstracts and the methodological validity of the records using data extraction format before their inclusion in the final review. Discussions with the senior author (M.E) were used to resolve any disagreements among the reviewers during the assessment phase. The inclusion criterion was: All studies evaluating the ef- fects and consequences of ED crowding. However, a study was excluded if it only reported the outcomes of a case re- port or systematic review investigations. A total of 73 articles were eligible for the review (Figure 1). We further assessed the records using the standardized Critical Appraisal Skills Programme (CASP) for the Cohort Studies, and Qualitative Studies. Besides, the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument ( JBI-MAStARI) for studies which employed other designs was used (7). We addressed PRISMA checklist requirements. Finally, after ex- cluding 15 records with eligibility assessment scores below 0.33 points (<33%), the final review was done on 59 records. Throughout the processes, we attempted to maintain the original intentions of authors such as effects on patients, ef- fects on healthcare delivery process, effects on quality care, and effects on efficiency in service delivery. Ethics approval and consent: The research protocol was ap- proved by the review committee of the Baqiyatallah Univer- sity of Medical Sciences. 3. Results: Our search initially retrieved 158 studies. However, 132 pa- pers were excluded by reviewing title and abstract and as- sessing full-text due to non-relevance. Then, 15 studies were excluded after final quality measurement and scoring for pri- mary screening due to receiving below 0.33 points (<33%). Finally, 58 eligible peer-reviewed original articles were in- cluded in the final review (Figure 1 and Table 2). The consequences of patient crowding in hospitals are multi- faceted involving effects related to patient health outcomes, healthcare delivery system and the community at large. Table 3 presents a summary of the commonly reported outcomes of ED crowding. ED crowding leads to delayed care for emer- gency patients and risk of not being visited by clinical care providers in a timely manner (8-14). The patients may react to prolonged stay to get services and to the crowding by fre- quent walkouts (15). The worsening of their illness (16) could result in frequent re-admissions (17, 18), prolonged hospital- izations (16, 19, 20), and related costs (21). Dissatisfaction of emergency patients (22-25), medication errors and adverse events (26-29), and patient death (16, 17, 19-21, 30-36) were also common consequences. The response to emergency and non-emergency patients in- fluences the quality of services provided, patients’ outcomes and the healthcare system. Discharge of patients even with high-risk clinical features (17) and diverting the patients to other facilities (37) might have affected the health outcomes. These conditions not only decrease admission rates (38) and prolong the time to receive and transfer outpatients (39), but also compromise the patients’ health outcomes and lead to high admission and re-admission rates (22, 36, 40) followed This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 3 Archives of Academic Emergency Medicine. 2019; 7 (1): e52 Table 1: Keywords used for searching published articles in databases Emergency department related concepts Crowding related concepts Outcome related concepts Controlled phrases Keywords Controlled term/phrase Keywords Keywords PubMed emergency medicine, pedi- atric emergency medicine, hospital emergency service, emergency medical services emergency, emer- gency medicine, pediatric emer- gency medicine, emergency medical services, emer- gency room, hospital emergency services, emergency health services, emergency department, emer- gency ward, ER, ED crowding crowding, over- crowded, crowded overcrowding, di- vert, diversion, congestion, surged, surging, capacity, crises, crisis, oc- cupancy, hospital bed utilization, bed, utilization Left without being seen (LWBS), Length of stay (LOS), de- layed treatment, satisfaction, adverse events mortality, morbidity, error, hospitalization, quality, perfor- mance, readmis- sions, overutiliza- tion, efficiency, cost EMBASE emergency ward, emergency medicine crowding, hospital bed utilization by a decrease in discharge rate of patients (17). In addition, the prolonged hospitalization of patients leads to overutiliza- tion of diagnostic and other laboratory facilities (40). The crowding of the EDs negatively influences both the healthcare delivery process and the outcomes. The high workload (41) results in delayed service provision, delayed clinical decision making, and increased length of stay (LOS) of patients (20, 21, 31, 35, 36, 40-54). These situations neg- atively influence the quality of services and efficiency (8, 14, 16, 36, 55-58). A properly managed medical emergency contributes to the prevention of the event in communities. For example, a successfully treated patient with community- acquired pneumonia will be less likely to transmit the disease to other community members (13). 4. Discussion This systematic review synthesized the outcomes related to ED crowding in hospitals. Crowding of ED can result in consequences for emergency patients’ health outcomes, the healthcare delivery system, and the community at large. The high inflow of emergency patients to ED leads to crowding of the ED, which can in turn negatively affect the health- care delivery process and outcomes. Delayed emergency healthcare service provision and patients leaving without be- ing seen (LWBS) (8-14) have been commonly identified as consequences of crowding. This condition could inevitably lead to increased walkout of patients due to the perceived high length of stay. As a result, the emergency patients’ mor- bidity worsened, and subsequent mortalities increased (16, 17, 19-21, 30-36). The frequent readmissions and prolonged hospitalizations of emergency patients not only increase ED crowding, but also negatively affect the cost of treatment (21) and patient satisfaction (22-25). Hoot and Aronsky in their systematic review identified a direct relationship between ED crowding and emergency patient death, reduced quality of care, and increased treatment costs (59). Delayed patient as- sessment and care provision could result in increased mor- tality, medical error, and decreased patient satisfaction (60). The increase in the workload of emergency healthcare staff due to the high patient flow results in delayed clinical deci- sion making and emergency healthcare service provision and increased ED LOS of patients (20, 21, 31, 35, 36, 40-42, 44-54, 61, 62). This condition again leads to discharge of patients even with high-risk clinical features (17) and to the diver- sion of emergency patients to other health facilities (37). ED crowding can also be associated with decreased admission rates (38), delayed emergency healthcare provision, and de- lay in transfer of emergency patients to inpatient wards (39). In contrast, the high admission and re-admission rates of emergency patients (22, 36, 40) followed by a decreased pa- tient discharge rates (17) and prolonged hospitalization can lead to overutilization of diagnostic imaging and laboratory tests (40). Thus, several emergency healthcare-related con- sequences seem to be overlooked in the Morley et al. syn- thesis as they mainly focused on inpatient LOS and ED LOS (60). Our review broadly highlighted the healthcare delivery system-related consequences of ED crowding under the cat- egories of healthcare delivery process, quality care, and effi- ciency. ED crowding can negatively affect the quality of emergency healthcare. The higher the number of emergency patients, the longer the time it takes to investigate their conditions and to take supportive actions (49). These conditions can lead to This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem H R. Rasouli et al. 4 Table 2: Studies examining outcomes of emergency department (ED) crowding Author Year Study Design Sample Quality Outcome variable Cremonesi, 2015 survey 54,254 patients High average per-patient cost; severity of health condi- tion Wang, 2015 prospective pilot 3139 patients High average length of stay (LOS); patient Left with- out being seen (LWBS) Shenoi, 2009 cross-sectional 63,780 admissions High diversion Fee, 2007 cross-sectional 39,000 visits High ED volume at the time of arrival Ben-Yakov, 2015 cohort 9,759 patients High ED crowding; patient disposition (admis- sion/discharge) Cha, 2011 regression 125,031 patients High mean patient volume over 8-hour; hospital mortality Chang, 2017 longitudinal 2,619 hospitals High LOS for admitted patients Chiu, 2017 cohort 70,222 visits High ED occupancy status; decision-making time; LOS; patient disposition Depinet, 2014 cross-sectional 9,976 patients High time to critically abnor- mal vital sign reassess- ment; patients waiting for admission, patients wait- ing in the lobby Derose, 2014 cohort 136,740 patients High inpatient mortality; ED LOS Dubin, 2013 retrospective 69 patients High emergency physician (EP) errors; number of patients boarding at the time of patient disposi- tion Epstein, 2012 cohort 533 patients High occurrence of pre- ventable medical errors; ED Occupancy Fee, 2011 cross-sectional 486 patients High arrival-to-antibiotic- administration times; number of ED patients requiring admission at the time of arrival Gabayan, 2015 cohort 625,096 visits High inpatient admission; death within 7 days Gaieski, 2017 cohort 2913 patients High ED occupancy; waiting patients; time to antibi- otics; mortality Hong, 2013 cross-sectional 1296 patients High delayed resuscitation ef- forts; hospital mortality Hsia, 2013 cross-sectional 3,368,527 patients High ED crowding; bounce- back admission Hwang, 2008 cross-sectional 1,068 patient High number of admitted pa- tients; pain care mea- sures Jo, 2012 cross-sectional 477 cases High 28-day mortality; timeli- ness of antibiotic therapy Jo, 2014 cross-sectional 54,410 patients High Emergency department occupancy ratio; ED LOS Jo, 2015 cross-sectional 1801 patients High ED occupancy ratio; in- patient mortality This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 5 Archives of Academic Emergency Medicine. 2019; 7 (1): e52 Table 2: Studies examining outcomes of emergency department (ED) crowding Risk factor Term n (%) Preterm n (%) P value Kennebeck, 2011 cohort 190 patients High ED crowding; timeliness of antibiotic administra- tion Kulstad,2009 cross-sectional 17 patients High time to the first elec- trocardiogram (ECG); time to patient arrival in catheterization labora- tory; occupancy rate Kulstad, 2010 observational NA High average daily occupancy rate and the emergency department work index (EDWIN) score; number of medication errors Lee, 2012 prospective review 11491 adults High ED crowding McCarthy, 2009 cohort 4 EDs High crowding at 30-minute intervals throughout each patient’s ED stay; waiting room time; treat- ment time; and boarding time; occupancy rate McCusker, 2014 cohort 677,475 patients High 30-day outcomes: mor- tality, return ED visits, oc- cupancy ratio separately for ED bed and waiting room patients Medley, 2010 prospective review 6,640 imaging studies High number of radiology studies ordered per patient; occupancy rate Michelson, 2012 cohort 198,778 visits High ED occupancy rate; re- turn visits to the ED within 48 hours Mills, 2009 cross-sectional 976 patients High administration of and de- lays in time to analgesia Mills, 2010 prospective cohort 767 patients High ED crowding; time from triage to computed to- mography (CT) read Muller, 2015 cross-sectional 40 ED bed High time to initial physician assessment; and daily nursing hours Mullins, 2014 ecological 4810 hospitals High LWBS; waiting times; boarding times; and LOS for admitted and discharged patients O’Connor, 2014 pilot 500 patients High triage time; date; treat- ment area; time to physi- cian initial assessment; return ED visits within 14 days Pines, 2007 cohort 694 patients High delay (>4 hours from ar- rival) Pines, 2007 cross-sectional 741 patients High ED crowding Pines, 2008 cohort 1,469 patients High ED crowding (hallway placement, waiting times, and boarding times); patient satisfac- tion This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem H R. Rasouli et al. 6 Table 2: Studies examining outcomes of emergency department (ED) crowding Pines, 2008 cohort 13,758 patients High Poor care; a delay (>1 hour) from triage to first pain medication; a de- lay (>1 hour) from room placement to first pain medication Pines, 2009 cross-sectional 4574 patients High inpatient adverse out- comes Pines, 2010 retrospective cohort 1,716 patients High ED crowding; ED occu- pancy, waiting patients, admitted patients, and patient-hours); overall LOS; time to treatment Reznek, 2017 retrospective 463 patients High Door-to-Imaging Time (DIT) within the 25- minute goal Shenoi, 2011 cross-sectional 161 patients High ED census; time to anal- gesic administration Shin, 2013 retrospective 770 patients High ED occupancy rate; com- pliance Sikka, 2010 correlation 334 patients High overall time to antibiotic administration Sills, 2011 cross-sectional 927 patients High ED occupancy; num- ber waiting to see an attending-level physician Sun, 2013 cohort 995,379 ED visits, 187 hospitals High inpatient mortality; hos- pital length of stay; costs Tekwani, 2013 cross-sectional 1591 surveys High ED crowding; hospital di- version status; satisfac- tion van der Linden, 2014 cohort 169 patients High walkout from emergency Van Der Linden, 2016 retrospective 39110 patient High time to triage; time to treatment; age; 24-h mor- tality; 10-day mortality. van der Linden,2016 cross-sectional 49539 patient High occupancy ratio; ED oc- cupancy; LOS; time to triage Verelst, 2015 cohort 108,229 patients High in-hospital death; hospi- tal; acquired morbidities; total hospital stay Wang, 2017 cohort 1345 participants High ED crowding; patient real-time satisfaction. Ward, 2015 cross-sectional 405 hospitals High admitted LOS; discharged LOS; boarding time; wait- ing time Wiler, 2013 cross-sectional 87,705 visits High patient LWBS Wu, 2015 cohort 852 patients High inpatient outcomes Phillips, 2017 cohort 2,557 patients High ED LOS Higginson, 2017 cross-sectional NA High bed occupancy Geelhoed, 2012 quasi-experimental NA High mortality rates; over- crowding rates reduced emergency healthcare quality and poor healthcare outcomes, which may result in an increase in bed occupancy rate (63). Besides, these conditions may negatively affect per- formances and result in inefficiency due to an increase in treatment costs (8, 14, 16, 36, 55, 56, 58). Similarly, others also identified the negative influence of ED crowding on the cost of treatment (59) and non-adherence to best practice guide- lines for emergency service provision (60). This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 7 Archives of Academic Emergency Medicine. 2019; 7 (1): e52 Table 3: Effects of crowding in emergency departments Effects on patients Delayed assessment or treatment; not being seen; not given care (8-14) Increased walkouts due to perceived ED length of stay (LOS) (15) Morbidity (16) Frequent readmissions (17, 18) Prolonged hospitalization (16, 19, 20) The high cost of treatment (21) Low satisfaction (22-25) Medication errors and adverse events (26-29) Mortality (16, 17, 19-21, 30-36) Healthcare delivery system process High workload (41) Delayed service provision/decision making and increased ED LOS (20, 21, 31, 35, 36, 40-54) Discharging patients with high-risk clinical features (17) Diverting patients to other facilities to reduce load (37) High patient re-admission rate (22) Decreased admission of patients due to crowding (38) Decreased discharge rate of patients despite crowding (17) High patient admission rate to general wards and ICU (40) Overutilization of diagnostic imaging and laboratory tests (40) Prolonged time to receive and transfer outpatients (39) Effects on quality care Shorter time to investigate patients’ conditions (49) Poor infection prevention and control measures (63) Low compliance with standards of care (19) Compromised quality of care (12, 22, 41, 51, 57, 64-66) High bed occupancy rate Effects on efficiency in service delivery Poor performance, low efficiency, and high cost of care/treatment (8, 14, 16, 36, 55, 56, 58) 4.1. Strengths and Limitation This systematic review synthesized original articles related to outcomes of the emergency department crowding in hos- pitals globally. Several studies identified complex issues re- lated to emergency department crowding. Our review iden- tified several crowding-related challenges and consequences including patient and staff reactions. The relevant original articles on ED crowding were accessed from the PubMed, Embase, and google scholar databases using comprehensive search keywords. The qualities of the records have been as- sessed using relevant checklists and those with low quality have been excluded. Our review also adds to the compre- hensiveness of the view about the issues. The more explicit schematization of our synthesis compared to other existing reviews can facilitate a better understanding of the complex phenomenon. However, this review has certain limitations. It used study reports published only in English retrieved from the two mentioned sources. Moreover, the reviewed studies did not have a shared definition of crowding. 5. Conclusion ED crowding affects individual patients, healthcare systems and communities at large. The negative influences of crowd- ing on healthcare service delivery result in delayed service delivery, poor quality care, and inefficiency; all negatively affecting the emergency patients’ healthcare outcomes, in turn. This review highlights the importance of response to emergencies and emergency-related crowding and pre- venting the consequences to better address the healthcare needs of emergency patients and increase the effectiveness of healthcare service delivery centers. 6. Acknowledgements Not applicable. 6.1. Authors Contributions All the authors have contributed to development of the concept and production of the final manuscript. Authors ORCIDs Sardollah Mahmoodi: 0000-0001-7077-6144 Hassan Goodarzi: 0000-0002-8640-6639 6.2. Funding Support Not applicable. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem H R. Rasouli et al. 8 6.3. Conflict of Interest No conflicts of interest. 6.4. Availability of data and supporting materi- als The datasets used and analyzed during the current study are available from the corresponding author on request. References 1. Higginson I. Emergency department crowding. Emerg Med J. 2012;29(6):437-43. 2. Derlet RW, Richards JR. Ten solutions for emergency department crowding. Western Journal of Emergency Medicine. 2008;9(1):24. 3. Makama JG, Iribhogbe P, Ameh EA. Overcrowding of acci- dent & emergency units: is it a growing concern in Nige- ria? African health sciences. 2015;15(2):457-65. 4. Rathlev NK, Chessare J, Olshaker J, Obendorfer D, Mehta SD, Rothenhaus T, et al. Time series analysis of vari- ables associated with daily mean emergency depart- ment length of stay. Annals of emergency medicine. 2007;49(3):265-71. 5. Yarmohammadian MH, Rezaei F, Haghshenas A, Tavakoli N. Overcrowding in emergency departments: a review of strategies to decrease future challenges. Journal of re- search in medical sciences: the official journal of Isfahan University of Medical Sciences. 2017;22. 6. Iraqi IJ, Mahmoudi H. Causes and Consequences of Emergency Department Overcrowding; Methods for Re- solving it. Health Research. 2016;1(4):239-44. 7. Erren M, Reinecke H, Junker R, Fobker M, Schulte H, Schurek JO, et al. Systemic inflammatory parameters in patients with atherosclerosis of the coronary and periph- eral arteries. Arteriosclerosis, thrombosis, and vascular biology. 1999;19(10):2355-63. 8. Depinet HE, Iyer SB, Hornung R, Timm NL, Byczkowski TL. The effect of emergency department crowding on reassessment of children with critically abnormal vital signs. Academic Emergency Medicine. 2014;21(10):1116- 20. 9. Gaieski DF, Agarwal AK, Mikkelsen ME, Drumheller B, Sante SC, Shofer FS, et al. The impact of ED crowding on early interventions and mortality in patients with severe sepsis. The American journal of emergency medicine. 2017;35(7):953-60. 10. Wang H, Robinson RD, Cowden CD, Gorman VA, Cook CD, Gicheru EK, et al. Use of the SONET score to evalu- ate Urgent Care Center overcrowding: a prospective pilot study. BMJ open. 2015;5(4):e006860. 11. Wiler JL, Bolandifar E, Griffey RT, Poirier RF, Olsen T. An emergency department patient flow model based on queueing theory principles. Academic Emergency Medicine. 2013;20(9):939-46. 12. Pines JM, Hollander JE. Emergency department crowd- ing is associated with poor care for patients with severe pain. Annals of emergency medicine. 2008;51(1):1-5. 13. Fee C, Weber EJ, Maak CA, Bacchetti P. Effect of emer- gency department crowding on time to antibiotics in pa- tients admitted with community-acquired pneumonia. Annals of emergency medicine. 2007;50(5):501-9. e1. 14. Reznek MA, Murray E, Youngren MN, Durham NT, Michael SS. Door-to-imaging time for acute stroke pa- tients is adversely affected by emergency department crowding. Stroke. 2017;48(1):49-54. 15. van der Linden MC, Lindeboom R, van der Linden N, van den Brand CL, Lam RC, Lucas C, et al. Walkouts from the emergency department: characteristics, rea- sons and medical care needs. European Journal of Emer- gency Medicine. 2014;21(5):354-9. 16. Verelst S, Wouters P, Gillet J-B, Van den Berghe G. Emer- gency department crowding in relation to in-hospital adverse medical events: a large prospective observa- tional cohort study. The Journal of emergency medicine. 2015;49(6):949-61. 17. Ben-Yakov M, Kapral MK, Fang J, Li S, Vermeulen MJ, Schull MJ. The association between emergency depart- ment crowding and the disposition of patients with tran- sient ischemic attack or minor stroke. Academic Emer- gency Medicine. 2015;22(10):1145-54. 18. Hsia RY, Asch SM, Weiss RE, Zingmond D, Gabayan G, Liang L-J, et al. Is emergency department crowding asso- ciated with increased “bounceback” admissions? Medi- cal care. 2013;51(11). 19. Shin TG, Jo IJ, Choi DJ, Kang MJ, Jeon K, Suh GY, et al. The adverse effect of emergency department crowding on compliance with the resuscitation bundle in the man- agement of severe sepsis and septic shock. Critical Care. 2013;17(5):R224. 20. Cha WC, Do Shin S, Cho JS, Song KJ, Singer AJ, Kwak YH. The association between crowding and mortality in admitted pediatric patients from mixed adult-pediatric emergency departments in Korea. Pediatric emergency care. 2011;27(12):1136-41. 21. Sun BC, Hsia RY, Weiss RE, Zingmond D, Liang L-J, Han W, et al. Effect of emergency department crowding on outcomes of admitted patients. Annals of emergency medicine. 2013;61(6):605-11. e6. 22. Mullins PM, Pines JM. National ED crowding and hos- pital quality: results from the 2013 Hospital Compare data. The American journal of emergency medicine. 2014;32(6):634-9. 23. Pines JM, Iyer S, Disbot M, Hollander JE, Shofer FS, Dat- This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 9 Archives of Academic Emergency Medicine. 2019; 7 (1): e52 ner EM. The effect of emergency department crowding on patient satisfaction for admitted patients. Academic Emergency Medicine. 2008;15(9):825-31. 24. Tekwani KL, Kerem Y, Mistry CD, Sayger BM, Kulstad EB. Emergency department crowding is associated with re- duced satisfaction scores in patients discharged from the emergency department. Western Journal of Emergency Medicine. 2013;14(1):11. 25. Wang H, Ojha RP, Robinson RD, Jackson BE, Shaikh SA, Cowden CD, et al. Optimal measurement interval for emergency department crowding estimation tools. An- nals of emergency medicine. 2017;70(5):632-9. e4. 26. Dubin J, Blumenthal J, Milzman D. 127 Emergency De- partment Crowding and Physician Inexperience are Syn- ergistically Associated With Increased Physician Errors. Annals of Emergency Medicine. 2013;62(4). 27. Epstein SK, Huckins DS, Liu SW, Pallin DJ, Sullivan AF, Lipton RI, et al. Emergency department crowding and risk of preventable medical errors. Internal and emer- gency medicine. 2012;7(2):173-80. 28. Kulstad EB, Sikka R, Sweis RT, Kelley KM, Rzechula KH. ED overcrowding is associated with an increased fre- quency of medication errors. The American journal of emergency medicine. 2010;28(3):304-9. 29. Pines JM, Pollack Jr CV, Diercks DB, Chang AM, Shofer FS, Hollander JE. The association between emergency department crowding and adverse cardiovascular out- comes in patients with chest pain. Academic Emergency Medicine. 2009;16(7):617-25. 30. Derose SF, Gabayan GZ, Chiu VY, Yiu SC, Sun BC. Emer- gency department crowding predicts admission length- of-stay but not mortality in a large health system. Medi- cal care. 2014;52(7):602. 31. Hong KJ, Do Shin S, Song KJ, Cha WC, Cho JS. Associ- ation between ED crowding and delay in resuscitation effort. The American journal of emergency medicine. 2013;31(3):509-15. 32. Jo S, Jeong T, Jin YH, Lee JB, Yoon J, Park B. ED crowding is associated with inpatient mortality among critically ill patients admitted via the ED: post hoc analysis from a retrospective study. The American journal of emergency medicine. 2015;33(12):1725-31. 33. Jo S, Jin YH, Lee JB, Jeong T, Yoon J, Park B. Emergency department occupancy ratio is associated with increased early mortality. The Journal of emergency medicine. 2014;46(2):241-9. 34. McCusker J, Vadeboncoeur A, Levesque JF, Ciampi A, Belzile E. Increases in emergency department occupancy are associated with adverse 30-day outcomes. Academic Emergency Medicine. 2014;21(10):1092-100. 35. Van Der Linden N, Van Der Linden MC, Richards JR, Derlet RW, Grootendorst DC, Van Den Brand CL. Ef- fects of emergency department crowding on the de- livery of timely care in an inner-city hospital in the Netherlands. European Journal of Emergency Medicine. 2016;23(5):337-43. 36. Wu D, Zhou X, Ye L, Gan J, Zhang M. Emergency depart- ment crowding and the performance of damage control resuscitation in major trauma patients with hemorrhagic shock. Academic Emergency Medicine. 2015;22(8):915- 21. 37. Shenoi RP, Ma L, Jones J, Frost M, Seo M, Begley CE. Ambulance diversion as a proxy for emergency depart- ment crowding: the effect on pediatric mortality in a metropolitan area. Academic emergency medicine. 2009;16(2):116-23. 38. Michelson KA, Monuteaux MC, Stack AM, Bachur RG. Pediatric emergency department crowding is associated with a lower likelihood of hospital admission. Academic Emergency Medicine. 2012;19(7):816-20. 39. Ward MJ, Baker O, Schuur JD. Association of emergency department length of stay and crowding for patients with ST-elevation myocardial infarction. Western Journal of Emergency Medicine. 2015;16(7):1067. 40. Chiu I-M, Lin Y-R, Syue Y-J, Kung C-T, Wu K-H, Li C-J. The influence of crowding on clinical practice in the emer- gency department. The American journal of emergency medicine. 2018;36(1):56-60. 41. Fee C, Weber EJ, Bacchetti P, Maak CA. Effect of emer- gency department crowding on pneumonia admission care components. The American journal of managed care. 2011;17(4):269-78. 42. Gabayan GZ, Derose SF, Chiu VY, Yiu SC, Sarkisian CA, Jones JP, et al. Emergency department crowding and out- comes after emergency department discharge. Annals of emergency medicine. 2015;66(5):483-92. e5. 43. Huang EP-C, Liu SS-H, Fang C-C, Chou H-C, Wang C-H, Yen Z-S, et al. The impact of adding clinical assistants on patient waiting time in a crowded emergency depart- ment. Emerg Med J. 2013;30(12):1017-9. 44. Kennebeck SS, Timm NL, Kurowski EM, Byczkowski TL, Reeves SD. The association of emergency department crowding and time to antibiotics in febrile neonates. Aca- demic Emergency Medicine. 2011;18(12):1380-5. 45. Kulstad EB, Kelley KM. Overcrowding is associated with delays in percutaneous coronary intervention for acute myocardial infarction. International journal of emer- gency medicine. 2009;2(3):149. 46. McCarthy ML, Zeger SL, Ding R, Levin SR, Desmond JS, Lee J, et al. Crowding delays treatment and length- ens emergency department length of stay, even among high-acuity patients. Annals of emergency medicine. 2009;54(4):492-503. e4. 47. Mills AM, Baumann BM, Chen EH, Zhang K-Y, Glaspey This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem H R. Rasouli et al. 10 LJ, Hollander JE, et al. The impact of crowding on time until abdominal CT interpretation in emergency depart- ment patients with acute abdominal pain. Postgraduate medicine. 2010;122(1):75-81. 48. Mills AM, Shofer FS, Chen EH, Hollander JE, Pines JM. The association between emergency department crowding and analgesia administration in acute ab- dominal pain patients. Academic Emergency Medicine. 2009;16(7):603-8. 49. O’Connor E, Gatien M, Weir C, Calder L. Evaluating the effect of emergency department crowding on triage des- tination. International journal of emergency medicine. 2014;7(1):16. 50. Phillips JL, Jackson BE, Fagan EL, Arze SE, Major B, Zenarosa NR, et al. Overcrowding and its association with patient outcomes in a median-low volume emer- gency department. Journal of clinical medicine research. 2017;9(11):911. 51. Pines JM, Localio AR, Hollander JE, Baxt WG, Lee H, Phillips C, et al. The impact of emergency department crowding measures on time to antibiotics for patients with community-acquired pneumonia. Annals of emer- gency medicine. 2007;50(5):510-6. 52. Pines JM, Prabhu A, Hilton JA, Hollander JE, Datner EM. The effect of emergency department crowding on length of stay and medication treatment times in dis- charged patients with acute asthma. Academic Emer- gency Medicine. 2010;17(8):834-9. 53. Sikka R, Mehta S, Kaucky C, Kulstad EB. ED crowding is associated with an increased time to pneumonia treat- ment. The American journal of emergency medicine. 2010;28(7):809-12. 54. van der Linden MC, Meester BE, van der Linden N. Emer- gency department crowding affects triage processes. In- ternational emergency nursing. 2016;29:27-31. 55. Shenoi R, Ma L, Syblik D, Yusuf S. Emergency department crowding and analgesic delay in pediatric sickle cell pain crises. Pediatric emergency care. 2011;27(10):911-7. 56. Cremonesi P, di Bella E, Montefiori M, Persico L. The ro- bustness and effectiveness of the triage system at times of overcrowding and the extra costs due to inappropri- ate use of emergency departments. Applied health eco- nomics and health policy. 2015;13(5):507-14. 57. Chang AM, Lin A, Fu R, McConnell KJ, Sun B. Associ- ations of Emergency Department Length of Stay With Publicly Reported Quality-of-care Measures. Academic Emergency Medicine. 2017;24(2):246-50. 58. Medley D, Morris J, Stone C, PCC CC, FFP FFP. CROWD- ING AND PHYSICIAN PRACTICE: AN ASSOCIATION BE- TWEEN EMERGENCY DEPARTMENT CROWDING AND RATES OF IMAGING STUDIES ORDERED BY PHYSI- CIANS. 59. Hoot NR, Aronsky D. Systematic review of emergency de- partment crowding: causes, effects, and solutions. An- nals of emergency medicine. 2008;52(2):126-36. e1. 60. Morley C, Unwin M, Peterson GM, Stankovich J, Kins- man L. Emergency department crowding: A systematic review of causes, consequences and solutions. PloS one. 2018;13(8):e0203316. 61. Graham J, Aitken ME, Shirm S. Correlation of measures of patient acuity with measures of crowding in a pedi- atric emergency department. Pediatric emergency care. 2011;27(8):706-9. 62. Hwang U, Richardson L, Livote E, Harris B, Spencer N, Sean Morrison R. Emergency department crowding and decreased quality of pain care. Academic Emergency Medicine. 2008;15(12):1248-55. 63. Muller MP, Carter E, Siddiqui N, Larson E. Hand hy- giene compliance in an emergency department: the effect of crowding. Academic Emergency Medicine. 2015;22(10):1218-21. 64. Lee C-C, Lee N-Y, Chuang M-C, Chen P-L, Chang C-M, Ko W-C. The impact of overcrowding on the bacterial con- tamination of blood cultures in the ED. The American journal of emergency medicine. 2012;30(6):839-45. 65. Sills MR, Fairclough D, Ranade D, Kahn MG. Emergency department crowding is associated with decreased qual- ity of care for children with acute asthma. Annals of emergency medicine. 2011;57(3):191-200. e7. 66. Higginson I, Kehoe A, Whyatt J, Smith JE. The 4-hour standard is a meaningful quality indicator: correlation of performance with emergency department crowding. Eu- ropean Journal of Emergency Medicine. 2017;24(1):25-8. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem Introduction Methods: Results: Discussion Conclusion Acknowledgements References