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.

Compare this with the harms experienced as a result of crowding, which are often probabilistic (e.g., patients in crowded EDs are at increased risk for delays, but not all patients experience delays), distributed (e.g., in crowded EDs, some patients may experience reduced privacy in hallway beds whereas, others do not), and hard to distinguish from a non-crowded baseline expectation (e.g., harms from a 30-minute delay in antibiotic administration might be invisible to both the patient and the care team).

It appears much easier for people and institutions to justify extraordinary action to address the highly acute, visible, and life-altering harm of the MCI than the pernicious, less visible and sometimes theoretical harm of ED crowding. The ethical underpinnings for this difference, supported by appeals to distributive justice and consequentialism, hold that when health care resources are limited, those whose needs are greatest should receive priority.⁷ In short, the needs of victims of an MCI are generally more acute than the needs of those experiencing ED crowding, and so vigorous plans to address their needs are potentially justified.

Rarity Versus Frequency

A second significant difference is in their relative frequency. It seems difficult for systems to justify extraordinary efforts to ameliorate the supply/demand mismatch of crowding because the mismatch itself is created by the misaligned economics of health care against which hospitals struggle to survive.⁸ Given the rarity of MCIs, extraordinary measures are viewed as feasible to implement whereas for everyday crowding they are not.

The same ethical precept that justifies extraordinary responses to MCIs—that when health care resources are limited, those with the greatest need should be prioritized—also justifies significant responses to crowding. This is because acutely ill or undifferentiated ED patients are generally in more significant need of diagnostic testing and advanced care than other patients who outcompete ED patients for resources, i.e., elective surgical patients for whom inpatient beds are held or inpatients who overstay their need for acute care.⁴

Moreover, although health systems may find it easier to justify extraordinary efforts for MCIs, this does not justify the lack of action to benefit the crowded ED patients—especially as most effective evidence-based strategies to combat crowding are uncomplicated and relatively inexpensive, including off-hours availability of both ambulatory and ancillary inpatient services, smoothing elective admissions and surgeries, inpatient hallway boarding, and active bed management.⁸

Ultimately, we agree that the same moral urgency, operational innovation, and resource allocation that is devoted to MCI response by health systems should also be applied to crowding.⁹ Process changes used to extend ED capacity during MCI events should be implemented continually when the crowding is at a crisis proportion. Algorithms should be developed that help hospital and ED operational leaders know what actions to take based on ED census and need for additional resources, regardless of whether they are caused by an MCI, or other acute influx of ED patients, or the hospital being over its inpatient capacity. MCIs are inherently unpredictable and EDs that proactively manage patient flow across the continuum ensure timely access to resources, including space, equipment, and staff, during acute disasters.

Vignette Closure 

Your ED received 23 blast injury patients, and although it was disruptive, the disaster plans that were in place were enacted, and the ED was able to make space to care for the patients from the MCI. After seeing how this MCI was handled, hospital and ED administrators started to work with the ED leadership to develop high capacity plans similar to disaster plans and to seek to enact them all the time so that the ethical issues of disparate patient care are addressed.

Dr. Marshall is vice chair of operations and associate professor of emergency medicine at the University of Kansas Medical Center.

Dr. Leigh is an associate professor of emergency medicine and palliative medicine at Cleveland Clinic Akron General in Akron, Ohio. 

Dr. Sauder is a community emergency physician, practicing in the Dayton, Ohio, area. 

Dr. Bookman is vice chair and professor of emergency medicine at the University of Colorado School of Medicine.

References

1. Hendrickson RG, Horowitz B. Disaster Preparedness. In: Tintinalli JE, Ma O, Yealy DM, Meckler GD, Stapczynski J, Cline DM, Thomas SH. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 9e. McGraw-Hill Education; 2020. 
2. Andress K, Hanfling D. Disaster Planning and Response. In: Strauss & Mayer’s Emergency Department Management. ACEP; 2021.
3. ACEP. Crowding (policy statement). https://www.acep.org/patient-care/policy-statements/crowding.
4. Moskop JC, Sklar DP, Geiderman JM, et al. Emergency department crowding, part 1–concept, causes, and moral consequences. Ann Emerg Med. 2009;53(5):605-611.
5. Moskop, JC, Geiderman, JM, Marshall KD, et al. Another look at the persistent moral problem of emergency department crowding. Annals of Emerg Med. 2019;74(3):357-364.
6. Moskop JC, Sklar DP, Geiderman JM, et al. Emergency department crowding, part 2–barriers to reform and strategies to overcome them. Ann Emerg Med. 2009;53(5):612-617.
7. Moskop JC, Iserson KV. Triage in medicine, part II: Underlying values and principles. Ann Emerg Med. 2007;49(3):282-287.
8. Kelen GD, Wolfe R, D’Onofrio G, et al. Emergency department crowding: the canary in the health care system. NEJM Catalyst. https://catalyst.nejm.org/doi/full/10.1056/CAT.21.0217. Published September 28, 2021. Accessed June 14, 2025.
9. McNeilly BP, Lawner BJ, Chizmar TP. The chronicity of emergency department crowding and rethinking the temporal boundaries of disaster medicine. Ann Emerg Med. 2023;81(3):282-285.