Mass Casualty Incidents: An Introduction for Imagers

Mark P. Bernstein
Clinical Associate Professor, Trauma and Emergency Radiology
NYU Langone Medical Center and Bellevue Hospital

The events of the Columbine school shooting in 1999, the attacks on September 11, 2001, and the anthrax mailings the following week underscored the need for health care to be prepared to respond to acts of mass violence and bioterrorism.

Many health care systems developed disaster preparedness plans, assuming that treatment would be delivered according to established standards of care with sufficient resources and facilities to serve their communities. However, with each subsequent mass casualty event it became apparent—at least in the immediate response, referred to as the “surge”—that resources were overwhelmed and delivery of health care to established standards was compromised. Consequently, health care systems needed to review and revise their disaster management plans with newly identified issues and renewed preparations.

Mass casualty incidents (MCIs) are not defined by number of victims or severity of injuries, but rather by an imbalance of supply and demand. Therefore, the definition is fluid, dependent upon the demand for and availability of limited resources to provide optimal care for a population of casualties.

The World Health Organization defines a mass casualty incident as “an event which generates more patients at one time than locally available resources can manage using routine procedures. It requires exceptional emergency arrangements and additional or extraordinary assistance." The key message being that there is no threshold.

Multiple Casualties vs Mass Casualties

In daily operations of normal emergency care, there is an abundance of resources in relation to patient load. In this setting, health care follows our routine standard of care operations. When the emergency department experiences an influx of multiple patients in a short period of time, without overwhelming resources, this is simply a busy shift. In this multiple casualties scenario, although extra resources may be marshaled, there is no significant deviation from normal standard of care. In contrast, a mass casualty results from a rapid patient load that quickly overwhelms available resources with necessary changes to the delivery of care.

MCIs may be natural, in the form of tornadoes, hurricanes, or floods; or they may be accidental, such as a building collapse or train crash; or they may be intentional, including mass shootings, riots, or explosive detonations. What MCIs share, however, is that these events are uncommon, unpredictable, and often occur without warning. Thus, responding to these events requires planning and practice.

The Greatest Good for the Greatest Number

The goal of health care in an MCI is optimizing outcomes for the greatest number of patients. Accordingly, changes in the usual standards of care are imperative to achieve this goal. Rather than doing everything possible to save every life, it will be necessary to allocate limited resources in a different manner, due to overwhelming demand. Those resources include operating rooms (ORs), interventional radiology (IR) suites, ventilation equipment, blood products, physical space in the emergency department, and imaging equipment—to name just a few.

To that end, several considerations need to be addressed, including:

  • How should current standards of care be altered in response to an MCI to save as many lives as possible?
  • What is the minimal acceptable care?
  • What issues and principles should guide the planning of a medical response for an MCI?
  • What information, tools, and resources are available to address the needs of planners?
  • When and how are non-trauma centers integrated into the response and care for an MCI?

Many disaster management plans do not provide guidance concerning altered standards of care necessary to respond to an MCI. Allocation of limited resources should be considered and planned for to ensure that access is both clinically sound and just.

Triage: Red, Green, or Yellow?

Triage is the act of sorting patients according to severity of injury, likelihood of survival, and availability of resources. It is a dynamic process, as resource accessibility changes (e.g., running out of ORs) and as patient condition changes (e.g., patient responds to fluid resuscitation and tourniquet application; conversely, a once stable “walking wounded” patient has suddenly decompensated). Moreover, triage needs to be flexible enough to respond to changes in MCI type and magnitude.

The sorting process serves to identify those patients in need of immediate medical attention, tagged red; patients with minor injuries that can clearly wait (i.e., walking wounded), tagged green; and patients who are tagged neither red nor green. These yellow-tagged patients require urgent, though not immediate medical care, repeat physical examinations, and often benefit from imaging to improve triage accuracy.

Human resources should also be considered, along with physical resources, to ensure a prolonged supply of qualified staff. Such considerations include staff transport into and out of the facility, nourishment, protection, adequate rest, and stress management.

Avoiding the Bottleneck

Multiple studies report CT and portable x-rays have created consistent bottlenecks during MCIs. The role of imaging is to improve triage accuracy: identify life threatening injuries to determine who is most in need of critical resources, including the OR, IR suite, or other life-saving measures. Detailed diagnosis at this stage to identify each and every rib fracture is not the mission in an MCI. Keep in mind that if the purpose of casualties coming to a hospital is to access such lifesaving resources, then a process modifier, such as imaging, should not be the rate-limiting step forming a bottleneck.

Essential radiological tasks are threefold: first, identify surgical and interventional cases; second, communicate critical results; and third, reduce over-triage to the OR.

During the surge, imaging should be limited to yellow-tagged and select red-tagged patients (those awaiting OR to prioritize).

Radiography during the surge phase of an MCI should be limited to portable chest x-rays to prevent misuse of non-emergent radiographs while other patients are waiting. No other radiographs should be allowed, until clearance from the senior triage physician.

CT scanning during the surge should be limited to high-priority hemodynamically stable patients and those responding to resuscitation.

Consider limiting scan protocols to a single whole-body CT (WBCT) to eliminate variation for optimal efficiency and greatest throughput. Imaging in an MCI is a departure from daily practice. CT is a limited-resource triage modifier and should always be viewed as such to prevent a bottleneck.

Imaging strategies include: a dedicated radiologist stationed at the CT console for immediate review; use of a paper form for critical imaging results; “no frills” WBCT protocols to eliminate immediate post-processing of multiplanar reformations, in favor of volume reading on a dedicated CT workstation, where possible; and consideration of thicker image slices, if scanner processing and/or hospital network is slow. Remember that spinal precautions can be maintained until after the surge, and reconstructions can be performed later, as necessary.

It is important to recognize that although CT usage during the MCI surge will be selective and may be altogether avoided, CT volumes will predictably increase post-surge. Post-surge imaging in an MCI may take up to 72 hours to complete; ensure staff are available beyond the initial phase.

Integration Is Preparation

Mass casualty events are increasing in frequency, creating stress on the hospital system as a whole, including the radiology department. Because dealing with an MCI presents a departure from routine standard of care, radiology must be incorporated into the hospital’s overall disaster management plan. Considering and understanding the issues the radiology department faces, as well as the role radiologists play in planning for these incidents, is vital for saving lives and improving outcomes.

The question is no longer if, but rather when, your department will become involved in some capacity. The need to be prepared is self-evident, and history has shown this requirement applies to all practice types, yet the integration of imaging into the MCI response remains a relatively novel concept—and can seem like an overwhelming one.

When planning and preparing for hospital-based medical care during disasters and mass casualties, radiologists must act as subject matter experts on the crucial role imaging plays. Proper integration can help develop a ready and resilient response that optimizes efficient and effective care while conserving vital resources.

The opinions expressed in InPractice magazine are those of the author(s); they do not necessarily reflect the viewpoint or position of the editors, reviewers, or publisher.