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The effects of emergency department overcrowding on admitted patient outcomes

a systematic review protocol

Santos, Eduardo; Cardoso, Daniela; Queirós, Paulo; Cunha, Madalena; Rodrigues, Manuel; Apóstolo, João

Author Information
JBI Database of Systematic Reviews and Implementation Reports: May 2016 - Volume 14 - Issue 5 - p 96-102
doi: 10.11124/JBISRIR-2016-002562
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Overcrowding in the emergency department (ED) has become an increasingly significant public health problem in the last decade1 and is described as the most serious problem that affects the reliability of healthcare systems worldwide.2–4

For many authors, ED overcrowding is defined as a situation where the demand for emergency services exceeds the ability to provide quality care within appropriate time frames.4–7 However, it is a consequence of simultaneous increasing demand for health care and a deficit in available hospital beds, for example during mass casualty incidents, but also in other situations causing a shortage of hospital beds.1,6 In this regard, overcrowding is the product of several hospital internal and external factors, and the most relevant are the insufficient access to hospital beds, and shortage of ED nursing and physician staff.1

The etiology of crowding is believed to be multifactorial, with several elements contributing to its cause: a decrease in hospital capacity, an increase in closures of a significant number of EDs, an increase in ED patient volumes, a shortage of nursing staff, an increase in the complexity of patient management and the inability to transfer patients from the ED to inpatient units.7

This reality is intensified because several studies have clearly demonstrated that overcrowding can lead to patients’ unwanted outcomes waiting for care: adverse events (overcrowding leads to increased medical errors), increased morbidity and mortality,8–11 prolonged length-of-stay,12 delay in door-to-needle time to treatment,7,13–17 reduced patient and staff satisfaction18 and an overall inferior health care.1

Although EDs are being closely scrutinized for their ability to meet quality benchmarks, the impact of their volume is often not recognized. In fact, demonstrating a relationship between volume and quality of care is important in bringing resources to bear in solving the crowding issue, as well as improving the ability to meet quality benchmarks.15 In the meanwhile, patient suffering, prolonged wait times, deteriorating levels of service and the ability to retain experienced staff in an ED are all ill effects of this ongoing problem.2–5 Despite increased political, administrative and public awareness, ED overcrowding situations continue to rise in frequency and severity.5

It should be noted that hospital administrative units must realize that overcrowding is not solely an ED problem, and governments must realize that this is a public health crisis and allocate resources accordingly because it is a serious patient-safety issue. However, allocation of resources and reimbursement rates do not reflect this.1

A preliminary search of the JBI Database of Systematic Reviews and Implementation Reports, the Cochrane Database of Systematic Reviews, Prospero, CINAHL and Medline revealed that there are currently no systematic reviews (neither published nor in progress) on the effects of ED overcrowding on outcomes of admitted patients. There are several literature reviews about this issue; however, they present relevant methodological limitations such as non-existence of two reviewers independently searching studies and grading each article for the strength of the evidence, risk-of-bias, too restricted inclusion criteria (e.g. only English language), lack of search in grey literature and single database searched.3,4,19

Therefore, it is necessary to perform a systematic review to determine the effects of ED overcrowding on outcomes of admitted patients, which involves an intense critical analysis based on scientific evidence because it affects the performance on measures of quality of care. For that reason, it is possible that EDs may need to revise their operations to meet the growing challenge of delivering time-sensitive treatments for trauma, sepsis, stroke and acute coronary syndrome patients.

Inclusion criteria

Types of participants

This review will consider studies that include adult patients, aged 18 years or more' in ED settings only.

Types of exposure

This review will consider studies that evaluate the exposure of admitted patients to ED overcrowding.

Overcrowding in the ED is defined as “a situation in which the demand for emergency services exceeds the ability of an ED (ED) to provide quality care within appropriate time frames”.5(p.1)

We will exclude overcrowding related to disasters/catastrophies.


This review will consider studies that compare adult patients in overcrowded ED units versus not crowded ED units. Studies without comparator will also be included.


This review will consider studies that include the following outcome measures:

  • Primary outcome – mortality
  • Secondary outcomes – hospital length-of-stay, time to antibiotic, time to thrombolysis and time to analgesic.

Types of studies

This review will consider epidemiological study designs and prospective and retrospective cohort studies, before and after studies, case-control studies and analytical cross-sectional studies for inclusion.

Search strategy

The search strategy aims at finding both published and unpublished studies. A three-step search strategy will be used in this review. An initial limited search of MEDLINE and CINAHL will be undertaken, followed by an analysis of text words in the titles and abstracts, and of the index terms used to describe the article. A second search using all identified keywords and index terms will then be undertaken across all included databases. Third, the reference list of all identified reports and articles will be searched for additional studies. Studies published in Portuguese, English and Spanish will be considered for inclusion in this review. Studies published from 1989 (this was the year ED crowding was first described20,21 and first studies started to appear according to our preliminary database search) will be considered for inclusion in this review. Studies in another language or date of publication will be excluded.

The databases to be searched include:

  • MedicLatina
  • CINAHL Complete
  • MEDLINE Complete
  • Cochrane Central Register of Controlled Trials
  • Scielo – Scientific Electronic Library Online

The search for unpublished studies will include:

  • ProQuest – Nursing and Allied Health Source Dissertations
  • Banco de teses da CAPES (
  • RCAAP – Repositório Científico de Acesso Aberto de Portugal
  • OpenGrey – System for Information on Grey Literature in Europe

Initial keywords to be used will be: emergenc*, critical care, crowd*, occupancy, capacity, congest*, mortality, length of stay, time to treatment.

Assessment of methodological quality

Papers selected for retrieval will be assessed by two independent reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI) (Appendix I). Any disagreements that arise between the reviewers will be resolved through discussion or with a third reviewer.

Data extraction

Data will be extracted from papers included in the review independently by two reviewers, using the standardized data extraction tool from the JBI-MAStARI (Appendix II). Data extracted will include specific details about the interventions, populations, study methods and outcomes of significance to the review question and specific objectives. For missing information or to clarify unclear data, the authors of primary studies will be contacted. Any disagreements that arise between the reviewers will be resolved through discussion or with a third reviewer.

A draft charting table was developed at the protocol stage to record the key information on which type of data we expect to find and how we intend to evaluate them; however, this may be further refined for use for at the review stage. Some key information that may be charted is as follows: author(s); year of publication; setting (country); study methods; aim/purpose; intervention/types of exposures; effect of ED crowding on main outcomes (mortality incidence proportion, hospital length-of-stay, time to antibiotic, time to thrombolysis, time to analgesic) and conclusions.

Data synthesis

Quantitative data will, where possible, be pooled in statistical meta-analysis using the JBI-MAStARI. All results will be subject to double data entry. Effect sizes expressed as odds ratio (for dichotomous data), weighted mean differences (for continuous data) and their 95% confidence intervals will be calculated for outcome analysis. Heterogeneity will be statistically assessed using the standard Chi-square and also explored using subgroup analyses on the basis of different quantitative study designs and types of participants, included in this review. Where statistical pooling is not possible, the findings will be presented in narrative form including tables and figures to aid in data presentation.

Appendix I: Appraisal instruments

MAStARI appraisal instrument


Appendix II: Data extraction instruments

MAStARI data extraction instrument



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Critical care; crowding; emergency medical services; outcome assessment (health care); patient safety

© 2016 by Lippincott williams & Wilkins, Inc.