System Resilience In Mass Casualty Incidents: Graceful Extensibility

Mass casualty incidents (MCIs) are, mercifully, rare. But when they arrive, they don’t knock—they tear the doors off. Whether it’s a natural disaster, an act of terror, or the steady violence of war, these events reveal what healthcare systems are truly made of. Protocols offer only partial maps; it is the capacity to adapt in real time, to stretch without snapping, that determines whether a system holds or folds.

Responding to MCIs is as much a test of institutional resilience as it is of human ingenuity, a quiet reckoning that plays out in hallways, triage tents, and operating rooms, far from the public eye. In this first of a 3-part commentary, we start by getting a flavor of what makes a work system resilient, by reflecting on an organization's capacity to continue functioning in the presence of abnormal stress and disturbances.

Sunrise Hospital & the 2017 Las Vegas Shooting

The New York Times has compiled a timeline of the Las Vegas shooting, based on online videos stitched together.

On the night of October 1, 2017, the Las Vegas desert air buzzed with panic and gunfire. Positioned high above a country music festival, a gunman opened fire, sending thousands fleeing and hundreds bleeding. Sunrise Hospital, just a few miles away, was suddenly transformed from a busy emergency department into the frontline of the deadliest mass shooting in modern U.S. history.

Manning the emergency department (ED) was Dr. Kevin Menes was on duty at the emergency department (ED) that night. He and his colleagues took a "non-standard" approach even before the first patient arrived. The hospital's response to this MCI could be mapped onto four key abilities of resilient systems described in many resilience engineering literature.

Response was dynamic and expansive. The emergency department operated at more than four times its usual capacity, with staff improvising triage stations in parking lots and hallways, reassigning roles across specialties, and repurposing stretchers and barricades as gurneys. With only four ED doctors and one trauma surgeon on duty that night, all off-duty nurses, doctors, and support staff were mobilized.

Monitoring was strategic and continuous. Clinicians utilized a modified triage color code to track and proactively catch deteriorating patients in real time. As resources such as manpower and services kept changing, the team worked to stay aware of and coordinated their deployment. Dr Menes periodically scanned the whole operation for choke points, and reassigned staff to keep the flowing moving.

Anticipation began with Dr Menes listening to the police radio and recognizing the sound of automatic gunfire, triggering early action before formal notification. He focused on opening and staffing more operating rooms so that patients did not deteriorate in an ED bottleneck. Buffets of etomidate, succinylcholine, and O- bloods were made available to by-pass the automated medication dispensing machines. Patients were cannulated during triage, since they will eventually undergo surgery. The early IV access also allowed for quick response when they decompensated. All this created a sense of timely proactiveness.

Learning emerged both during and after the event. Staff drew on prior military or trauma experiences, as well as recognized how team cohesion and prior preparedness shaped their effectiveness and the overall performance outcome. Everyone adjusted previously-defined plans in response to new information and unfolding realities.

Four Basic Potentials of Resilient Performance

These four abilities reflect a system's potential to be resilient: knowing what to do, what to look for, what to learn and improve, and what lies ahead. They are deeply entangled capacities, each sharpening the other, and forming the scaffolding for a successful, resilient performance. They thus are good starting points to analyze whether an organization's MCI response were due to deliberate design, training, and foresight, or merely the fortunate alignment of improvisation, individual heroics, and chance.

The Four Abilities of a Resilient System can be mapped out using the FRAM model to reflect their interdependence. Source

One might argue that a team’s ability to "wing it" is a mark of resilience. But true resilience is rarely accidental. It is less about emergency brilliance and more about the quiet groundwork that makes improvisation possible: the drills no one remembers, the mental models refined and rehearsed, the trust that builds over years of ordinary work. In the crucible of a mass casualty event, it’s not heroism that carries the day—but preparation, pattern recognition, and the ability to act with fluid precision. Resilience is not the absence of surprise, but the ability to meet it with something more than luck.

Graceful Extensibility

At the heart of Sunrise Hospital’s response was what resilience engineers call graceful extensibility, the capacity to stretch just enough to absorb the unimaginable without falling apart. It’s what allowed this 52-bed emergency department to hold hundreds, through a combination of modified protocols, MacGyver-like resourcefulness, and swift reactions at the systems level. Graceful extensibility isn’t just about scaling up, but about holding together.

And yet, that stretch should remain the exception, not the expectation. A system built to bend in crisis is not meant to live in a constant state of tension, endlessly compensating for chronic insufficiencies. When resilience becomes routine, it stops feeling heroic and starts feeling like survival. Over time, even the most flexible system fatigues, the most cohesive teams fray.

In the end, resilient performance should not hang by a thread, fearing the arrival of the proverbial back-breaking straw. Nor should it feel like “another day, another disaster.” MCIs offer a rare, if painful, opportunity to test, improve, and prepare. A system intentionally designed to safely accommodate surges becomes a quiet assurance, reminding us that even in the most unthinkable moments, we are not merely bracing for impact, but ready to rise.