KEY DEFINITIONS

A mass casualty event is defined as a situation in which the number of patients and the severity of their injuries exceed the capability of the facility to deliver care in a routine fashion. The appropriate initial response is to treat patients sustaining major injuries with the greatest chance of survival first so that valuable resources are not expended on patients with little hope of survival.

A multiple casualty event is defined as a situation in which the facility can mobilize additional resources in response to a large number of patients so as to continue to deliver care in a relatively routine fashion. The optimal field management of a mass casualty event is to convert it into a multiple casualty event for each receiving hospital. If appropriate distribution of victims to facilities occurs, the number of patients and the severity of their injuries will not exceed the ability of a facility to render care.

Triage refers to the medical sorting of patients according to their need for treatment and the available resources. In a mass casualty event, conventional standards of medical care cannot be delivered to all victims. The goal of triage is to optimize care for the maximum number of salvageable patients.

Patients are triaged into four categories at the scene: minor, delayed, immediate, and dead. In military triage systems, a fifth category, expectant care, is used for patients with a small chance of survival who would use scarce resources to such an extent as to adversely affect the chance of survival of other more salvageable patients. This category is rarely used in civilian situations as mobilization of additional personnel resources is usually possible. Numbers, colors, or symbols may be used to denote the categories (Table 1). “Undertriage” refers to assignment of patients to a level of care inadequate for their level of injury. An under-triage rate greater than 5% is unacceptable as it may lead to unnecessary morbidity and mortality in severely injured patients. “Overtriage” refers to assignment of patients to a level of care greater than required for their level of injury. An overtriage rate of 50% is considered acceptable to minimize undertriage. Excessive overtriage at the scene threatens the response of the entire system due to expenditure of limited resources on the wrong patients.

Table 1 The Four Colors of Triage

Adapted from Los Angeles Community Emergency Response Team.

PREHOSPITAL CARE IN MASS CASUALTY EVENT

The response to a mass casualty event requires the coordinated effort of many agencies with disparate cultures, command structures, and even communications equipment (Figure 1). Appropriate agencies should submit to the authority of the incident field commander at the scene. Prior joint training can break down these barriers and improve overall response to the event.

Figure 1 Components of disaster response.

Whether the event is caused by an accident, an intentional attack, or a natural disaster, the area of the event must be secured. In the event of a terrorist or military attack with conventional weapons, additional enemy operatives must be identified and neutralized. The area must be searched for additional unexploded ordinance and if found it must be either disarmed or exploded in a safe area. If these principles are not followed, the probability of a “second hit” is significantly increased.

Victims must be extracted, concentrated in a safe area, and triaged. Immediate care patients should be transported first, but often require management of airway, breathing, and circulation problems.

Transportation of victims from the scene to the hospital does not always occur in formal ambulances. Buses and private vehicles are sometimes used. Worried well persons and patients with minor injuries sometimes self-triage to hospitals without the knowledge of the incident field commander, leading to increased confusion and inundating the receiving hospitals.

Crowd control at the scene is a major problem. Multiple volunteers with various skills arrive to help and hinder. The triage area should optimally be secured and individuals inserted to help at the discretion of the triage commander.

HOSPITAL TRIAGE

If either a large number of casualties suddenly arrive without warning, or the hospital is informed of their impending arrival, the hospital should initiate its mass casualty plan. In a true mass casualty event, all area hospitals must participate in the care of victims to avoid exhaustion of the resources of any one facility. The common goal is salvaging as many lives as possible. A contingency plan for patients not involved in the mass casualty event must be in place as part of emergency preparedness. This plan permits the hospital to convert to mass casualty mode in a short period of time.

In preparation to receive and care for multiple victims, all elective surgery must be cancelled. Rapid disposition of pre-existing patients in the emergency department (ED) is required. Depending on the size of the event, hospitalized patients who are fit may be discharged and patients transferred within the hospital if required to maximize the availability of surgical beds.

The initial hospital triage (Figure 2) should occur outside the ED as patients arrive by ambulance. Ideally, ambulances should pass through a security checkpoint prior to entrance to the hospital grounds to identify terrorists or ordinance that may be on board. Initial triage need not be done by a surgeon, but should be done by a highly experienced clinician. If possible, the walking wounded should be escorted through a separate entrance.

Figure 2 Initial triage stations.

As soon as stretcher patients enter the ED, a senior surgeon should triage each patient to either immediate or delayed care (see Figure 2). The immediate treatment area should be reserved for salvageable patients with life-threatening problems. This area should have enough space for equipment and provide a one-way flow of traffic. The following personnel should be present at each bed in the immediate care area: a senior surgeon for decision making, an anesthesiologist to provide airway control, two ED or critical care nurses, and a junior surgeon for vascular access and tube thoracostomy as necessary.

Treatment in the immediate care area is based upon the principles of advanced trauma life support. The goals of therapy in the immediate care area are airway control, ventilation, cessation of external hemorrhage, vascular access, and rapid transfer of the patient to the next appropriate treatment station, usually the intensive care unit (ICU) or the operating room (OR), for completion of the primary and secondary surveys and further diagnostic or therapeutic interventions. Factors affecting the decision as to where to perform the secondary survey and the patient’s ultimate disposition include the patient’s condition and the number of immediate care patients (Figure 3). This decision should be made by a senior surgeon.

Figure 3 Intra-hospital traffic flow.

Prior arrangements should be made to expand the ICU. The postanesthesia care unit is an ideal venue for expansion of ICU services. Since most victims do not require immediate access to the OR (unless they have penetrating trauma due to shrapnel, or traumatic amputations), even empty ORs could be used to temporarily manage critically ill patients in an unusual situation.

Patients with significant but non–life-threatening injuries are triaged to delayed care. A junior surgeon and nurse should be assigned to each of these delayed care patients. A senior surgeon, however, should be in charge of the delayed care area and the area designated for the walking wounded in order to provide advice and correct any errors in triage that may have been made.

Many of the walking wounded from a mass casualty event are not transported by emergency medical services. Civilian transport can make up as much as 80% of victims arriving at hospitals, often causing overtriage at the closest hospitals to the event. Most of the walking wounded patients can be discharged from the ED. Many of these patients require psychological counseling and support and should be screened for psychological trauma.

HOSPITAL EMERGENCY INCIDENT COMMAND SYSTEM

The Incident Command System in the United States was developed in the 1980s in order to improve command and control of firefighters in complex operations. An adaptation of that system, the Hospital Emergency Incident Command System (HEICS), is quickly becoming the standard for hospital disaster management. The goal of any disaster management scheme is to create an efficient system of care that will both save lives and return the hospital to routine function as soon as possible. The advantages of the HEICS include a predictable chain of command and a common language to facilitate communication among disparate agencies coordinating the response to the event.

The basic principle of HEICS is that one individual supervises no more than five people and reports to only one person. A senior surgeon is the ideal incident commander. This system allows for efficient and manageable lines of communication and easy accountability. There are four main section chiefs: planning, logistics, finance, and operations. The operations chief has overall responsibility for the triage of victims and their clinical care, and potential coordination with other area hospitals (Figure 4).