Surge Capacity and Mass Casualty Incidents Preparedness of Emergency Departments in a Metropolitan City: a Regional Survey Study

Surge capacity refers to the ability to deal with the rapidly increasing patients who need to be admitted and use available resources in the event of a disaster or multiple injuries.1, 2 Surge capacity can be divided into three categories: the public health system's total capacity, the community's capacity, and a specific facility's capacity according to the host.3 Individual health care institutions play the role of “the first tier” in the earliest stages of a health care disaster response.4 Emergency departments (EDs) are always faced with ensuring patient safety by managing critical supply/demand mismatch, which is the main portal into the healthcare system.5

Measurement standards for surge capacity have not yet been developed, but there is a consensus on the main components, known as “4S's” for “staff,” “stuff,” “space,” and “systems.”6 It is difficult to measure a disaster surge objectively; most previous studies have proposed conceptual calculation methods based on theory and assumptions.7 It is difficult to define hospital surge capacity standardly as various studies have reported that it can increase up to 5 to 35% of hospital beds.8 Some consensus statements recommend raising the intensive care unit (ICU) expansion goal to 200% of usual capacity during a crisis.9

Several studies have quantitatively calculated surge capacity. In these studies' early paper, an increase by 3% of the number of beds per hour was suggested as hospital treatment capacity.10 In a study that calculated the surge capacity of a specific level 1 trauma center through computer modeling, the number of critical patients who could be treated per hour rose from 4.6 to 7.1.11 In another study, surge capacity was estimated by surveying the actual number of patients treated during the same day at 133 trauma centers.12 In studies benchmarking the above quantitative studies, hospital acute care surge capacity was defined as the number of ED beds divided by the ED time (2.5 hours).13

To date, qualitative and quantitative studies on surge capacity assume that the hospital's capacity can be maximized in case of a disaster or multiple casualty incidents (MCIs). Actual surge capacity can be severely limited due to overcrowding in hospitals and EDs, as it is currently required to maintain treatment continuity for all other patients.5 Therefore, enquiring EDs in a specific region about their official surge capacity and preparedness for MCIs can help measure the entire community's actual surge capacity and capability. We investigated the surge capacity of the specific number of accommodatable patients and overall preparedness at EDs in a metropolitan city. Moreover, we tried to estimate the city's surge capacity and analyze the hospital variables that affect surge capacity.

In this regional survey study, 31 regional and local EMCs were asked about the number of patients that could be accommodated within one hour in case of a disaster or multiple accidents. Assuming that KTAS 1–3 were emergency patients, about 300 patients (10 per hospital) were acceptable in the conventional phase. This number increased by 2.5 times in a crisis phase, with about 850 emergency patients (25 per hospital) throughout the city. To the best of the authors' knowledge, this is the first study in South Korea to investigate the surge capacity and preparedness for each hospital in a specific region when MCI or disasters occur.

In South Korea, regional EMCs play the role of disaster-based hospitals. The main task of such hospitals is dispatching DMATs to the scene; however, there is a dearth of focus on hospital preparedness and the surge capacity of each hospital.19 The Emergency Medical Response Manual for Disasters published by the Ministry of Health and Welfare is the primary basis for the disaster medical assistance system in South Korea.17 In this manual, a chapter is devoted to the hospital disaster response. However, it does not explicitly mention the definition and calculation method of surge capacity. It remains difficult to properly implement the even transfer of multiple casualties from the field to hospitals.20 Since 2014, the Disaster Emergency Medical Services Situation Room operated by the National Emergency Medical Center has been intermediating communication between the field and the hospital. When any MCI occurs, the situation room quickly checks the capacity of hospitals around the scene. The number of patients that can be accommodated is reported by each emergency medical facility, considering various resource situations. A method of checking directly with the person in-charge of each institution was selected in this study because each EMI determines its surge capacity in the actual situation.

There were no significant differences in the number of accommodatable patients in ordinariness or crisis conditions between regional EMCs and local EMCs. Regional EMC has more resources than local EMC, but the number of ED doctors remains the same. Several studies have shown that even if there was sufficient capacity for multiple casualties and disasters, a lack of medical personnel caused a decrease in staff occupied beds.21, 22 Patients generally begin to arrive approximately 15 to 30 minutes at EMCs, 50% of patients arrive within approximately an hour and 80% within 90 minutes.23, 24 Moreover, the hospital begins to suffer from a lack of medical resources within two hours.25, 26 It takes some time to activate the disaster plan and convene a medical team to respond to disasters and multiple casualties. Initially, EMCs have no choice but to cope with their existing medical staff. Therefore, despite the sufficient medical resources in regional EMCs, the absence of a difference in the number of medical staff (especially doctors) working in EMCs may have caused these results. As shown in Fig. 2, regional EMCs and local EMCs have different resources. Therefore, there is a possibility that regional EMCs will have more free space. However, there was no statistically significant difference in surge capacity for at least the first hour. If a surge occurs continuously for more than several hours, regional EMCs with more free space or resources could show higher surge capacity than local EMCs.

Because of limited surge capacity within an hour to accommodatable patients, the number of KTAS 1–3 patients that each regional and local EMCs can accommodate is smaller than expected. In a crisis, all regional and local EMCs in Seoul can accommodate 848 emergency patients. Several studies showed that although Surge capacity may vary slightly depending on each hospital's situation, it can increase the number of beds by 20%–30% quickly.3, 13, 27, 28 Initially, space is secured by moving patients in EMCs to the wards, using emergency space, and discharging patients hospitalized via the reverse triage.28, 29 In the United States, the Department of Health and Resources announced at least 500 beds for every one million residents for surge capacity to use in the event of a disaster.30, 31 In addition, the surge capacity is affected by the rate of occupied beds of the ward.30, 31, 32 According to the results of the 2016 survey in Korea, the percentage of occupied beds is almost 98% on average.33 The institutions that participated in this study had 800 beds to prepare for MCIs and disasters (about 82.5 beds per million people). Therefore, these high rates of occupied bed and lack of prepared space available for surge capacity may lead to a decrease in the number of accommodatable patients.

Misclassification and misallocation at the pre-hospital level significantly impact the patient's survival rate in a crisis.34, 35 There is at least one regional EMC and four local EMCs in one region, Seoul. Regional EMCs accommodate a minimum of 34 patients in crisis conditions, including at least two KTAS 1 patients and two KTAS 2 patients. Local EMCs also accommodate a minimum of 18 patients in these conditions, including the same KTAS 1 and KTAS 2 patients in regional EMCs. Therefore, when there are approximately 100 or more patients, it becomes beyond one area's capacity. Since regional EMCs and local EMCs can accommodate at least two KTAS l and KTAS 2 patients to help clarify the severe patients' allocation, patients can be distributed and transferred at the pre-hospital level one by one to regional and local EMCs. In this study, the scale of multiple casualty accidents or disasters was not simulated. The surge capacity was measured based on the increase in the frequency of simple visits. It was surveyed that all hospitals in Seoul can accommodate more than 300 KTAS 1 or 2 patients in the crisis phase. Therefore, it is theoretically possible to accept all severely injured patients from very large-scale disasters in Seoul. However, this assumes that the disaster emergency medical system works ideally. The development of sophisticated guidelines for on-site patient distribution and hospital accommodation is needed to apply them to real-world situations.

Hospital resource-related variables that can affect surge capacity were analyzed through multivariate regression analysis. The total number of hospital beds was only found to be significantly related to surge capacity. The number of ED beds and the number of doctors and nurses in the ED or hospital were highly correlated with hospital beds. Therefore, it can be interpreted that the overall hospital resources and surge capacity are related. Regulations on each hospital or role of EMC in a disaster situation did not seem to correlate significantly with surge capacity. Public support is needed so that hospitals with larger surge capacity can play a more important role in a disaster, or disaster-based hospitals can accommodate more casualties.

We did not analyze the quality of care in EMCs according to the size of the patient surge. However, as the size of the patient surge increases, the quality of care may decrease due to insufficient supply, which may result in poor clinical outcomes. For example, the quality of care in ordinariness and crisis may be different. In future studies, it is necessary to consider the quality of care provided according to the size of the patient surge.

This study has several limitations. First, the participants of this study were limited to regional and local EMC in Seoul. The resource situation of local EMI in Seoul may be different. For MCIs and disasters, the ED and other departments in the hospital will respond together. Therefore, even within the same hospital, departments other than the ED may have different opinions. Second, the surge capacity was measured by the official opinion of the ED director in this study. A third party did not objectively measure the surge capacity of the institution as only little is known about how to measure surge capacity easily. In actual MCI situations, the Disaster Emergency Medical Services Situation Room uses a method of directly asking each ED about the type and number of patients acceptable. Therefore, we think that the surge capacity measured in this study was quite close to reality. We propose a simulation study method to contact all EDs within a specific area on the same day to investigate acceptable patients. Third, it is not easy to match the field severity classification (e.g., SALT or START) with the KTAS classification. The surge capacity calculation formula was proposed through expert discussion within the committee, however, additional validation is needed. Fourth, this study mainly measured the hospital's capacity and did not measure the capability of the medical staff. Capabilities between hospitals of similar size may differ. Fifth, when measuring surge capacity, the number of patients the clinical workforce can handle per hour is essential. Unfortunately, this study did not investigate this variable separately. In this study, we assumed that patients due to multiple casualties occurred simultaneously. In this scenario, all patients were transferred to the hospital within the first hour, and the on-site situation was terminated. In the case of a catastrophic surge that spans hours or days, the incident command center of the hospital should consider the hospital's ability to handle it per hour. Finally, since this study was conducted in South Korea's largest metropolitan city, it has limitations in its generalization. It may not be easy to apply this study's results to other regions of South Korea or other countries.

In conclusion, at an average level of MCI, in which less than 20 immediate casualties occur in Seoul, it can be accommodated while maintaining the standard of routine care in each region. In the event of a greater level of MCI or disaster, EDs in the region may have to enter the crisis response stage. The surge capacity of a specific area can be estimated using the method used in this study. More detailed follow-up studies are needed to prepare a surge capacity protocol in the community.