A disaster is an event that overwhelms the ability of a community or health system to respond with its usual resources. Disasters may be natural (typhoons, floods, earthquakes, volcanic eruptions, pandemics) or human-made (transport crashes, explosions, chemical releases, terrorism, armed conflict). A mass casualty incident (MCI) is any event in which the number or severity of casualties exceeds immediately available resources.

The disaster cycle

Core principles of mass casualty care

• Safety first — rescuer, team, then survivors. An injured responder becomes another casualty.
• Do the greatest good for the greatest number — care shifts from the individual to the population.
• Crisis standards of care may apply when resources are critically short; decisions follow pre-approved protocols, not individual judgment alone.
• Unified command and clear communication through the incident command system (ICS).
• Documentation continues, even in simplified form (triage tags, casualty tracking).

Incident Command System (ICS): a standardized, scalable management structure with an Incident Commander and sections for Operations, Planning, Logistics, and Finance/Administration. Each person reports to one supervisor (unity of command) and has a defined role. The hospital version is the Hospital Incident Command System (HICS).

Scene size-up (first actions on arrival)

1. Is the scene safe? Fire, structural collapse, secondary devices, traffic, electrical hazards, chemical odors or clouds, multiple people collapsing without obvious cause (suggests a chemical agent).
2. Report to the incident command post and receive an assignment; do not self-deploy into the scene.
3. Estimate the number of casualties, the mechanism, and the resources needed.
4. Begin triage (see Topic 91): START or SALT for mass casualties.

Injury patterns by hazard

Psychological responses

• Most people show normal distress reactions: fear, sadness, sleep problems, poor concentration.
• Acute stress disorder: symptoms lasting 3 days to 1 month after the trauma (DSM-5-TR).
• Post-traumatic stress disorder (PTSD): intrusive memories, avoidance, negative mood, and hyperarousal lasting more than 1 month.
• Screen for suicidal thoughts, substance use, and inability to meet basic needs.

In disasters, "diagnostics" are mainly planning and assessment tools.

Hospital surge response

• Activate the EOP and HICS; establish a command center
• Create surge capacity: cancel elective procedures, early discharge of stable clients (reverse triage), open alternate care areas, call in staff
• Set up a decontamination area outside the emergency department entrance to prevent contaminating the building
• Establish family information and reunification areas and a media point

CBRNE basics

Personal protective equipment levels

Hospital nurses normally work in the warm or cold zone; entry into the hot zone is for trained hazmat responders.

Drug safety in CBRNE care

Listed in priority order.

1. Protect yourself and the team
   • Assess scene safety before approaching; wear PPE matched to the hazard; stay within your assigned zone
2. Triage and life-saving interventions
   • Rapid triage; control major bleeding (tourniquet), open the airway, decompress tension pneumothorax, give antidotes; then move on
   • Crush injury: start IV isotonic fluid (normal saline) before or during extrication and continue at high rates after release; avoid potassium-containing fluids; cardiac monitoring for hyperkalemia; aim for a high urine output
3. Decontamination when chemical or radiological exposure is suspected
   • Remove clothing and jewelry, bag and label them, rinse skin with water and mild soap; protect privacy and keep clients warm
4. Ongoing care and reassessment
   • Re-triage frequently — conditions change; track casualties to prevent lost clients
5. Shelter and public health
   • Adequate ventilation, hand-washing stations, and safe water and sanitation; separate or isolate clients with fever, cough, diarrhea, or rash; no shared personal hygiene items
   • Maintain chronic medications (insulin, antihypertensives, dialysis access, oxygen); identify vulnerable people (older adults, pregnant women, infants, people with disabilities)
   • Safe food handling; warn about carbon monoxide from generators and cooking indoors
6. Psychological first aid (PFA)
   • Provide safety, calm, and comfort; meet basic needs (water, food, shelter, information)
   • Listen without pressure; do not force people to describe the event
   • Connect people with family and support services; promote self-efficacy
   • Single-session psychological debriefing is not recommended
7. Staff well-being — rotate shifts, rest, peer support, recognize compassion fatigue

• Build a household emergency plan: meeting place, contact person outside the area, evacuation routes
• Prepare a "go bag": water, food, flashlight, radio, batteries, first-aid supplies, copies of documents, and at least several days of prescription medications with a written list
• Follow official warnings and evacuate early when advised
• Avoid wading in floodwater; wear boots; clean wounds promptly and seek care for fever after flood exposure
• Boil or treat drinking water when supply is unsafe; wash hands often
• Stress reactions after disasters are common and usually improve; seek help if sleep, mood, or daily function does not improve after several weeks or if thoughts of self-harm occur

• First action at any disaster scene: assess scene safety
• Disaster cycle: mitigation → preparedness → response → recovery
• MCI goal: greatest good for the greatest number
• HVA identifies and prioritizes hazards for planning; HICS is the hospital command structure used to run the response
• ICS sections: Operations, Planning, Logistics, Finance/Administration
• PPE: A = SCBA + vapor-tight suit; B = SCBA, less skin protection; C = air-purifying respirator (hospital decon); D = work clothes
• Decontamination: remove clothing first, then soap and water; decon area outside the ED
• Radiation: treat life threats before decontamination; time, distance, shielding
• Nerve agent: atropine titrated to dry secretions + pralidoxime
• Shelters: ventilation, hand hygiene, isolate febrile clients — not routine antibiotic prophylaxis (exception: Department of Health–advised doxycycline prophylaxis after flood exposure in the Philippines)
• PFA: safety, comfort, basic needs, connection; never force retelling
• PTSD requires symptoms lasting more than 1 month