Mass Casualty Incidents, Disaster Management & the Hospital's Role

Definitions and Taxonomy

Mass Casualty Incident (MCI)

A mass casualty incident is any event in which the number of casualties overwhelms the capacity of the local healthcare system to provide usual standards of care. Critically, MCI is defined not by absolute numbers but by the ratio of casualties to available resources. An MCI in a regional hospital with limited surge capacity may involve 10-15 patients; the same event near a major trauma centre may be manageable without activating full MCI protocols.

Disaster Classification

CBRN Subcategories

National and Hospital Disaster Frameworks

The PPRR Model

Australian emergency management is structured around four phases:

$$\text{Disaster Management} = \underbrace{Prevention}{\text{risk reduction}} + \underbrace{Preparedness}{\text planning} + \underbrace{Response}{\text{activation}} + \underbrace{Recovery}{\text{restoration}}$$

The ED is primarily involved in Response but must also contribute to Preparedness (staff training, drills, equipment stockpiles) and Recovery (ongoing surge capacity, psychological support).

Hospital Emergency Operations

Hospitals activate a Hospital Incident Command System (HICS) or equivalent during an MCI. Key components include:

• Hospital Incident Controller (often a senior medical administrator or ED director)
• Operations Section: clinical care coordination
• Logistics Section: equipment, pharmacy, blood bank
• Planning Section: situational awareness, resource tracking
• Finance/Administration: cost capture, media liaison

The ED Medical Director must understand their role within this hierarchy, typically leading clinical operations in the Emergency Department while maintaining communication upwards to the incident commander.

Triage in Mass Casualty Events

START Triage (Simple Triage and Rapid Treatment)

The primary field triage tool. Assesses three parameters in sequence:

Secondary Triage: SALT and SIEVE

Within the hospital, more detailed triage occurs at the entrance and in the ED using structured tools. The SIEVE and SORT approach (used in many Australasian systems) applies physiological parameters:

$$\text{Revised Trauma Score (RTS)} = (0.9368 \times GCS_{\text{coded}}) + (0.7326 \times SBP_{\text{coded}}) + (0.2908 \times RR_{\text{coded}})$$

An RTS < 7.84 predicts significant injury requiring immediate attention.

Triage Categories

The expectant category is the most ethically challenging for ED clinicians. Allocating a patient to expectant means withholding immediate life-saving intervention despite signs of life, because the resources required would deprive multiple others of survival. This is a fundamental departure from routine ED practice and requires explicit authorisation within the hospital's disaster plan.

Hospital Surge Capacity

The Four S Framework

Surge Levels

ED Operations During an MCI

Immediate ED Actions on Activation

1. Clear the ED: Accelerate discharge of existing patients; admit stable patients to wards
2. Establish triage point at the ambulance bay, not inside the department
3. Create work zones: resuscitation area (T1), urgent area (T2), minor treatment area (T3)
4. Activate blood bank and pharmacy protocols: pre-position O-negative blood, MTP activation
5. Don PPE appropriate to threat (standard precautions minimum; full CBRN for relevant incidents)
6. Establish command and communication: appoint ED triage officer, ED clinical coordinator, documentation officer
7. Maintain situational awareness: regular structured briefings to incident command (e.g. every 30 minutes)

Decontamination

For chemical, biological or radiological incidents:

• Hot zone: scene, not hospital responsibility
• Warm zone: decontamination corridor, typically outside ED at hospital perimeter
• Cold zone: clean area, inside ED post-decontamination
• All patients from CBRN incidents must be considered contaminated until cleared
• Secondary contamination of staff and other patients is a critical risk
• Decontamination involves clothing removal (removes ~80% of surface contamination), copious water irrigation, and specialist decontamination showers

CBRN-Specific Management Principles

Chemical Agents

Radiation

• Acute Radiation Syndrome (ARS) occurs at whole-body doses > 1-2 Gy
• Dose thresholds:

• ED management: ABC resuscitation, anti-emetics, barrier nursing, haematology liaison for G-CSF and bone marrow support
• Potassium iodide only for radioiodine (thyroid protection, given within 4 hours of exposure)

Communication and Coordination

Internal Communication

• Clear chain of command: triage officer → ED coordinator → hospital incident commander
• Closed-loop communication mandatory in high-noise, high-stakes environments
• Structured handover using ISBAR (Identify, Situation, Background, Assessment, Recommendation) adapted for MCI pace
• Regular timed updates to command (avoid continuous interruptions)

External Communication

• ED liaises with:
  • Ambulance command: casualty numbers, categories, ETAs
  • Other hospitals: load distribution, specialty availability, diversion decisions
  • Public Health Unit: for biological/CBRN events
  • Police / Fire / Emergency Services: scene safety, casualty access
• EMPLAN (or state-equivalent): the overarching emergency management framework that coordinates inter-agency response
• Media: all media communication via hospital media liaison, clinicians must not make independent public statements

Patient Tracking and Documentation

• MCI patient tracking systems (paper-based or electronic triage tags) must link field tag number to ED record
• Dedicated documentation officer reduces cognitive load on treating clinicians
• Facilitates family liaison, missing person identification, and medicolegal documentation

Ethical Dimensions of MCI Response

Utilitarian vs. Rights-Based Ethics

MCI triage is explicitly utilitarian, the greatest good for the greatest number. This conflicts with the individual patient-centred model of routine ED practice.

Key ethical tensions:

• Withholding CPR from cardiac arrests during MCI (standard practice, CPR consumes disproportionate resources with low yield in multi-casualty settings)
• Expectant categorisation of survivable but resource-intensive patients
• Allocation of scarce ventilators, blood products, or operating theatre time
• Equity of care across sociodemographic groups under stress

Do Not Attempt Resuscitation in MCI

During a declared MCI, most protocols recommend:

• No CPR for traumatic cardiac arrest unless isolated penetrating torso injury with very recent arrest
• No ROSC attempts for unwitnessed arrests in the field
• Explicit written policy in the hospital disaster plan provides legal and ethical cover for treating clinicians

Psychological Impact on Staff and Patients

Clinician Wellbeing

• MCI events carry high risk of acute stress reactions and post-traumatic stress disorder among responders
• Structured psychological first aid should be available immediately post-event
• Formal defusing (within hours) and debriefing (24-72 hours) should be planned, not ad hoc
• Team leaders must monitor for signs of cognitive overload, decision fatigue, and emotional numbing during prolonged events

Survivor and Family Needs

• Dedicated family liaison area, separate from clinical areas
• Consistent, accurate information flow
• Access to social work, chaplaincy, mental health liaison
• Medicolegal identification processes (police liaison)

ACEM Fellowship Implications

Written Examination Considerations

Candidates should be able to:

• Define MCI and distinguish from routine major trauma responses
• Accurately describe START triage and the rationale for expectant categorisation
• Apply the Four S surge framework to a clinical scenario
• Describe CBRN decontamination principles and specific antidote regimens (particularly organophosphate poisoning)
• Articulate the ethical framework underpinning MCI triage decisions

OSCE / Hot Case Application

In a disaster management OSCE station:

• Demonstrate systematic thinking: scene safety → decontamination → triage → command structure → resource allocation → communication
• Explicitly name the ethical conflict when asked about expectant categorisation, do not avoid it
• Identify that cardiac arrest management changes during an MCI and justify this decision
• Discuss the ED Medical Director's specific responsibilities: clinical coordination, surge activation, communication with incident command, and staff welfare
• Reference the hospital disaster plan as the enabling document for non-standard clinical decisions (e.g. withholding CPR, expectant tagging)

Governance and Preparedness

• Regular disaster drills (including unannounced in-situ simulations) are required to identify latent system failures before a real event
• After-action reviews and root cause analysis following drill activations drive system improvement
• ED physicians should be involved in disaster plan development and revision, not merely plan recipients
• Credentialing and scope-of-practice documents must account for extended roles during declared disasters (e.g. nurses performing triage, registrars leading resuscitation streams independently)
• Know your hospital's specific MCI activation thresholds, communication trees, and role assignments, these are examined in ACEM assessments and are life-critical in practice

Sources

• ACEM policy documents
• ANZCOR / ARC Resuscitation Guidelines