A Scoping Review of the Essential Components of Emergency Medical Response Systems for Mass Casualty Incidents

Abstract Objective: Emergency medical (EM) response systems require extensive coordination, particularly during mass casualty incidents (MCIs). The recognition of preparedness gaps and contextual priorities to MCI response capacity in low- and middle-income countries (LMICs) can be better understood through the components of EM reponse systems. This study aims to delineate essential components and provide a framework for effective emergency medical response to MCIs. Methods: A scoping review was conducted using 4 databases. Title and abstract screening was followed by full-text review. Thematic analysis was conducted to identify themes pertaining to the essential components and integration of EM response systems. Results: Of 20,456 screened citations, 181 articles were included in the analysis. Seven major and 40 sub-themes emerged from the content analysis as the essential components and supportive elements of MCI medical response. The essential components of MCI response were integrated into a framework demonstrating interrelated connections between essential and supportive elements. Conclusions: Definitions of essential components of EM response to MCIs vary considerably. Most literature pertaining to MCI response originates from high income countries with far fewer reports from LMICs. Integration of essential components is needed in different geopolitical and economic contexts to ensure an effective MCI emergency medical response.

effectiveness is necessary to assess preparedness for MCIs. Accordingly, the study team sought to answer the question: What are the essential components of an emergency medical response system in the immediate aftermath of an MCI?

Methods
As a guiding strategy, we focused on manmade MCIs, excluding events that did not leave an intact health system, given the disproportionately increasing number of manmade MCIs in LMICs. [13][14][15]

Search Strategy and Databases
A search strategy for peer-reviewed sources was developed in collaboration with a university informationist and modified for different databases. English language articles highlighting emergency response components, and relevant assessments, were identified through structured searches of PubMed, Embase, Global Health, and Scopus spanning a 20-year period from 2000 to 2020. Combinations of search terms, including medical subject headings and keywords, were organized in 3 groups: (1) mass casualty and emergency disasters; (2) response, preparedness, and planning; (3) instruments, measurements, evaluations, and assessments. Human subjects, year, and language restrictions were applied. The detailed search strategy adapted for each electronic database are included in the Supplementary Text S1. The "similar articles" section of the PubMed website and reference lists of the identified articles were also examined to capture other potentially relevant articles. All references were exported to Covidence (Melbourne, Australia) and duplicate studies were excluded. 16 This review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) format ( Figure 1).

Inclusion and Exclusion Criteria
Articles included in this review encompassed peer-reviewed English language studies, guidelines, tools, and instruments focused on outlining essential components and measures for evaluation of MCI response at the prehospital, hospital, city, and national levels. The inclusion criteria for citations were intentionally broad, capturing scientific publications, committee reports, evaluations, tools, organizational and governmental guidelines, and emergency preparedness plans and exercises. For the purposes of this review, MCIs that compromised the structural integrity of an emergency medical system or disrupted the ability to deliver emergency care through workforce attrition were not considered. Accordingly, large-scale public health emergencies, infectious outbreaks, and complex protracted humanitarian emergencies were excluded. Articles without full text available in English language were excluded from further analysis. Criteria of eligible studies are outlined in Table 1.

Data Abstraction
Seven team members (A.U., A.M., S.R., A.E., A.A., O.A., and J.D.) independently screened the titles and abstracts of all retrieved studies to identify the relevant studies according to the eligibility criteria, with each title and abstract screened by 2 separate reviewers. Conflicts were resolved by consensus among the reviewers during weekly research meetings, while remaining unsettled votes were arbitrated by the lead author (A.U.). After title and abstract screening, the studies underwent full-text review by the same independent reviewers. Studies were evaluated by the type of study, location, year of publication, key response components addressed, and methods of evaluation. Data extraction was performed using a data extraction sheet developed by 2 team members (A.U., A.M.). Included articles were organized by authors' name and year of publication with an indication of whether the article outlined response activities from a high-income country (HIC) or LMIC. The World Bank classification of countries by income was used to define low-income, lower middleincome, and middle-income countries; this classification is based on gross national income (GNI) per capita. 17

Data Analysis
Thematic analysis was performed by 2 team members (AU and AM) using traditional content analysis to evaluate the full text of each included article. 18 Emerging themes pertaining to the essential components and evaluation of emergency medical response systems were included. Domains or components of emergency medical responses most frequently mentioned and discussed within the included studies were designated as essential. Included studies were characterized according to the essential components explored (Supplementary Table S2), with quality assessment of the articles conducted with guidance from the Institute of Medicine Standards for Systematic Reviews. 19

Results
Of 20,456 screened citations, 181 articles were included in the qualitative analyses ( Figure 1). A large number of studies were observational and approximately a third of all articles included reports and resource documents as shown in Table 2. Most of the included studies, 165 of the 181, were in HIC contexts ( Figure 2). Seven major themes emerged from the content analysis as essential domains of an emergency medical response system: (1) communication; (2) safety and security; (3) human resources; (4) planning, policy, and procedures; (5) command, control, and coordination of the disaster response; (6) care delivery; and (7) health finance for disaster planning and response. Additionally, 40 sub-themes were found to support the essential components of an MCI response as shown in Table 3. A large number of publications focused on care delivery (67%), leadership and coordination (30%), communications (23%), and human resources (19%). Safety and security, as well as planning, policy, and procedures to execute response and assist recovery were also important domains identified in the literature. Each identified

Safety and Security
Safety and security must always be prioritized with any MCI, recognizing that some incidents, such as terror attacks or chemical hazards, require containment and pose a greater security threat than others. 13,32,34,37,39,47,54,59,62,75,[77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92] Moreover, security officials maintain the law and order at the scene and at the hospitals receiving injured patients, controlling access points, and restricting it to only authorized personnel, monitoring for suspicious activities, and preventing crowds from interfering with emergency operations. 13,32,34,39,40,47,49,59,62,73,81,87,[91][92][93][94] Deploying a safety officer to identify potential threats and implement appropriate safety procedures is essential in virtually all MCIs. 13,36,39,47,56,75,81,93 In response to the safety and security challenges adopted in some settings is the introduction of Tactical medicine, in which outof-hospital care is provided by specially trained practitioners, many with military and/or law enforcement training, who operate in hostile environments. 33   Care Delivery Care delivery is an umbrella term that covers a variety of operational and logistical activities. Approximately two-thirds of the articles, or 67%, covered clinical medical response for MCIs in the pre-hospital and hospital setting, discussing rational use of resources, triage, decontamination, surge capacity, stockpiles of medical supplies and equipment, bottlenecks in providing critical services, care of pediatric patients and other special populations, specialized management of burn injuries, and the unique considerations of chemical, biological, radiological and nuclear (CBRN)-related MCIs.

Disaster Medicine and Public Health Preparedness
Health Finance Seven of the included articles directly addressed the financing of MCI response. Financial resources, largely determined by the fiscal budget of the city government, determine the extent at which MCI response activities can be operationalized in an effective and timely manner. 20,27,29,44,87,89,96,104,124,126,130,132,151 Recognizing that there are many competing priorities for municipal funds, local government officials should perform annual hazard analyses to allocate resources corresponding to level of risk. 20,27,32,44,55,100,104,110,124,126,130,132,143,147,165

Discussion
With the premise that an effective and timely response saves lives, the immediate aftermath of an MCI deserves special attention. An effective MCI response minimizes chaos, misinformation, and delays in care. However, defining effectiveness is met with considerable variability. Here, we sought to characterize the essential domains and components of an emergency medical response, specifically pertaining to MCIs. The observed heterogeneity and complexity of emergency medical response system components during an MCI are by and large a function of the scope of the event on the affected population. System-level tools and assessments exist to improve disaster readiness but fall short of comprehensively capturing crucial activities in an MCI emergency medical response framework. 1,[199][200][201][202][203] The World Health Organization's (WHO) Emergency Response Framework (ERF) is geared toward emergencies with public health consequences that are outside of the definition of this study's defined MCI (eg, natural disasters, bioterrorism events, or pandemics) and limits its framework to the activities of the WHO. 201 Other frameworks such as the mass casualty management systems framework summarize comprehensive strategies and guidelines for building health sector capacity at the national level, provincial/state level, community and local government level, and health-care facility level. 203 Using the thematic analysis in this study, an Integrated Framework of MCI Response with the essential domains and components is presented in Figure 3. The framework highlights the connections and interrelatedness of different components, which is sometimes overlooked when studying one aspect of the MCI response. It is, therefore, imperative to remember how each of these component influences and shapes the other. Best practices pertaining to MCI response commonly emerge from real-world contexts and are often anecdotal. Real-world experience could better inform practices through more systematic collation and rigorous analysis. Few studies based on experimental design pertaining to MCI response were found in this review, likely attributable to the largely unpredictable nature of MCIs. Another notable observation was the predominant focus of literature on process outcomes, such as early MCI activation, EMS response time, shortened transit from scene to facility time, early injury identification, and efficient injury management. In contrast, only a few included articles presented data linking process improvements to improved health outcomes. 38,107,156,176,190 This suggests that further research is needed to explore how health and other impact outcomes are affected by improvements in process indicators. Furthermore, despite LMICs carrying the global burden of death and disability from MCIs, evidence concerning emergency response from these settings remain sparse. 204 The majority of the studies in this review are from high-income countries, potentially limiting generalizability to LMICs. The essential domains and components of an organized approach to MCIs can be adapted to LMICs but is not representative of the unique challenges facing low-resourced environments and, therefore, should be applied with caution. For instance, very limited information is available on the key responders representing institutions not typically involved in response in HICs. Additionally, many identified components of the emergency medical response were found to hinge upon the preparedness of regional medical centers and the presence of health-care infrastructure capable of providing emergency care services, which often is not as developed in LMICs. 205,206 More research taking into consideration the perspective of MCI response in LMIC settings is warranted. The predominance of descriptive, observational, and case studies provides lowquality of evidence related to education, training, clinical care, and in some instances, policy recommendations.

Limitations
Although this review focuses on the response phase of the disaster management cycle, it is recognized that effective emergency response cannot be separated from preparedness, mitigation, and recovery. Studies pertaining to these other phases were designated as outside of the scope of this review. The selected focus of this review centered on the subset of manmade MCIs due to their increasing frequency and high relevance to understanding emergency medical response capacity and may not necessarily be applicable to other events that are subacute or of a protracted nature. As stated in our findings, the literature on MCI is largely from high-resource settings, despite a relatively higher burden in LMICs. We believe the basic characteristics of a response system would remain the same irrespective of the setting and the specific roles of the individual institutions. Finally, MCIs of catastrophic proportions that resulted in complete disruption of health systems were not examined, and accordingly, findings may have limited generalizability outside of the scope of this review.

Conclusions
This study identified significant gaps in the available evidence on emergency health system response for MCIs, with much of the literature characterized as anecdotal. Most existing literature is also from high income countries, with far less evidence from low resource, particularly LMIC, settings. We identify 7 essential domains, 40 sub-components of an emergency medical response system, and introduce an Integrated Framework of MCI Response to highlight the interconnectedness of an MCI emergency response. The framework for MCI response is limited if it is not evaluated and implemented by key stakeholders in the immediate aftermath of an MCI. Further research on emergency response capacity for MCIs tailored to the LMIC context is greatly needed.