It is a busy Saturday evening in your emergency department (ED). Every bed is filled, including those in the hallways. The waiting room is packed, with some of the wait times exceeding six to eight hours. A stricken nurse hands over the phone, and a pressured voice comes through saying, “There was a bombing at a music festival. We don’t know how many, but ready the ED.”

A mass casualty incident (MCI) is defined as an event in which the number of patients overwhelms the resources of the hospital or local health care system. In other words, an event in which the ability to provide safe and timely care is exceeded by demand.^1,2 This definition bears remarkable resemblance to the concept of ED “crowding,” which ACEP defines as occurring “when the identified need for emergency services exceeds available resources for patient care in the ED, hospital, or both.”³

The similarity between crowding and MCIs makes it striking to compare the response plans and actual hospital responses to MCIs against the typical actions (or perhaps, inaction) hospitals take to respond to ED crowding.

Demand Exceeds Capacity

Crowding has been a regular problem for EDs for more than 30 years. Despite crowding and its mitigation being the subject of study, intervention, and advocacy at all levels of health care administration and policy, it remains endemic.^4-6 Crowding is harmful to patients, yet there is limited governmental or institutional will to meaningfully assist the patients being harmed. In contrast, health care systems generally stand prepared for MCIs with extensive plans.

Moreover, as a rule, MCIs in the United States are marked by extraordinarily effective responses, not only by physicians, but by the very health care systems and government agencies whose responses to ED crowding have proven so feeble. In fact, in some cases these remarkable MCI responses provide temporary relief to EDs marked by intractable crowding right up until the moment an MCI occurs (whether in ED decompression, extra staffing, or both).

If both patients involved in an MCI and patients in crowded EDs share the same moral feature of needing care when demand for care exceeds capacity, and justice includes the principle of treating people similarly when they share relevant features, is it unjust that these patients receive such dissimilar attention?

Although both crowding and MCI conditions share a core feature of supply/demand mismatch, they are different in key ways. The first key difference is in the types of harms caused to patients. MCIs cause harm that is both acute and visible, whereas crowding causes harm that is less visible, usually less acute, and mostly distributed and probabilistic. The harms experienced by patients in an MCI are injuries or illnesses that are a threat to their life or quality of life, are highly apparent compared with their pre-MCI baseline, and are amenable to timely treatment.