Major incident and disaster triage

• A major incident is any event that seriously threatens the health of the community, or produces so many casualties or such unusual injuries that the emergency and health services must put special arrangements in place. ^[4]
• Triage is the allocation of limited resources during a disaster: it puts the casualty who needs immediate care first, so the greatest number survive with what is available. ^[1]
• In one UK framework, a mass casualty incident is one on a scale beyond the normal resources of the emergency and healthcare services to manage; casualties are estimated to split roughly 25% needing life-saving treatment now (P1), 25% able to wait a short while (P2) and 50% walking wounded (P3). ^[4]
• START sorts adults in around 30 to 60 seconds by walking, breathing, pulse and ability to obey commands. SALT adds a sort stage and allows simple life-saving actions at the scene. ^[1][2][3]
• Clear information is passed by the METHANE report; hospitals respond with standby, triage, surge and (where needed) decontamination. ^[4][5]
• Understanding these systems matters in a CBRN or hazardous-materials incident, where ordinary trauma triage is modified by the need to protect staff and decontaminate casualties. ^[4]

By the end of this page you should be able to:

1. Define a major incident and a mass casualty incident, and say who declares one.
2. Describe the START and SALT triage algorithms and state their strengths and limits.
3. Build a METHANE report and explain why each letter matters.
4. Outline how an NHS hospital moves from standby to a declared major incident, including surge and flow.
5. Recognise a possible CBRN scene, apply the STEP 1-2-3 PLUS safety triggers, and state the principles of decontamination and nerve-agent casualty classification.
6. Apply the NHS Ten Second Triage and Major Incident Triage Tool (MITT) priorities (P1/P2/P3/dead or not breathing).
7. Describe the WHO emergency and disaster risk management approach to health-sector preparedness.

No health system has unlimited ambulances, operating theatres, critical care beds or blood. A major incident turns that abstract fact into an immediate choice about who is treated first. The goal of triage is not to do the best for the individual casualty in front of you in isolation; it is to secure the best outcome for the greatest number with what exists. ^[1]

Triage is a dynamic process, not a decision made once. A casualty's class can change as they are reassessed, and no triage system is known to be superior to the others in all settings. ^[1] The systems that follow are therefore tools to standardise thinking and communication, not recipes that replace clinical judgement.

A major incident is any occurrence that presents a serious threat to the health of the community, or causes such numbers or types of casualties as to require special arrangements to be implemented; for the NHS this includes any event defined as an "emergency" in section 6.4 of the NHS England Emergency Preparedness, Resilience and Response Framework. ^[4]

A "mass casualty incident for UK health resources" is an incident (or series of incidents) causing casualties on a scale that is beyond the normal resources of the emergency and healthcare services' ability to manage. ^[4]

Mechanism matters. In the UK, smaller incidents can combine geographically or over time to require a mass casualty response. Specialist services (for example burns) may activate their arrangements at a lower threshold because resources are limited. ^[4]

Who declares it: the police, fire and ambulance control rooms are usually first to spot unusual activity. They notify their on-call incident manager, who decides whether to escalate. A hospital may also "self-declare" a standby if there is an unexplained surge of casualties in the emergency department, or credible news of an emerging incident. ^[4]

Three stages are recognised: ^[1]

• Primary triage is done at the scene by an emergency technician or responder, aiming for a rapid assessment and rapid transfer.
• Secondary triage is used when the incident is large and pre-hospital transfer is delayed; it is performed by a doctor or surgeon as casualties arrive at hospital.
• Hospital (third) triage prioritises which casualties receive which definitive care, including operating theatre or intensive care.

Hospital triage systems used in everyday practice (Manchester Triage System, CTAS, Australasian Triage Scale, Emergency Severity Index) should still have a disaster plan written into them; every hospital should design a programme for triage during disasters and mass casualty incidents as part of its emergency plan. ^[1]

START (Simple Triage And Rapid Treatment) was developed in California by the Newport Beach Fire and Marine Department and Hoag Hospital; sources differ on whether this was 1980 or 1983. ^[1][2] It remains the most commonly used mass casualty triage algorithm in the United States. ^[2]

Key features: ^[1]

• It is used for injured adults older than 8 years. ^[1]
• Assessment is intended to take around 60 seconds or less, preferably 30 seconds. ^[1]
• The criteria are, in order: the ability to walk, respiratory rate, capillary refill, radial pulse and ability to obey commands.
• By combining them, a casualty is tagged red (immediate), yellow (delayed), green (minor) or black (dead or unlikely to survive).

The 1996 Benson modification substituted radial pulse for capillary refill, with reported improved accuracy, especially in cold weather. ^[2] A modified version (MSTART) drops the capillary refill criterion altogether, because it is unreliable in dark or cold environments. ^[1]

Only two therapeutic actions are allowed in standard START: opening the airway and controlling bleeding with direct pressure. ^[1] START has been one of the most widely used systems, but it has never been formally validated against clinical outcomes in a randomised trial; evidence to decide which system is best is lacking. ^[1]

SALT (Sort, Assess, Lifesaving Interventions, Treatment and/or Transport) is a CDC-sponsored triage concept launched in 2008 as a proposed national standard for the United States. ^[1][3] It was developed using the best available science and consensus opinion and is compliant with the Model Uniform Core Criteria for Mass Casualty Triage. ^[3]

The sort stage: ^[1]

1. Those who can walk to a designated area.
2. Those who can only move a limb or wave.
3. Those who do not move or show life-threatening problems; this last group is assessed first.

The assess stage then checks breathing (after opening the airway), peripheral pulse, obedience to commands and evidence of control of bleeding. ^[1]

Permitted life-saving actions are broader than START: opening the airway, controlling external bleeding, giving antidotes for some poisonings, and needle thoracostomy for a suspected tension pneumothorax. ^[1]

SALT is designed to be an "all-hazards" algorithm. In chemical, biological, radiological or nuclear (CBRN) incidents, a START-based algorithm with special measures (protection of the responder and decontamination) is recommended; there is little evidence yet for SALT's performance in CBRN conditions. ^[1]

Reverse triage gives priority to patients with minor injuries, so they can be treated, discharged and return to help others; it is also used to expand emergency department capacity during a disaster by discharging patients who can safely go without treatment for at least 96 hours. ^[1]

Burn incidents use their own triage, by depth and body surface area, with higher priority for children under 5, adults over 60, pregnant women and significant burns to special areas. ^[1] Children have their own systems, such as JumpSTART (under 8 years) and the Paediatric Triage Tape, because their physiology, heart failure after respiratory failure, and inability to walk or follow commands differ from adults. ^[1]

METHANE is the common model used to pass incident information between emergency services and their control rooms, and between pre-hospital and hospital teams. Using a shared format lets information be passed quickly and consistently, whoever is involved. ^[4]

Each letter: ^[4][5]

• M - Major incident. Has a major incident been declared? (At hospital: has the major incident standby message been sent?)
• E - Exact location of the incident and the best access routes.
• T - Type of incident and (as more is learned) the mechanism of injury.
• H - Hazards. Chemicals, fire, power lines, (suspected) CBRN substances, unstable structures.
• A - Access. Which routes are best for entry and exit; for hospitals, how casualties will arrive and egress routes.
• N - Number of casualties (by priority if known), and the estimated numbers expected over time.
• E - Emergency services involved or needed (ambulance, fire, police, and for hospitals, which hospital specialties).

A hospital receiving the first message should start its standby actions and be prepared to update or repeat the METHANE report. ^[4][5]

The NHS England Emergency Preparedness, Resilience and Response Clinical Reference Group developed two newer tools in 2023. They replace the older triage-sort approach, which performed poorly compared with the Modified Physiological Triage Tool at picking out patients needing life-saving intervention. ^[5]

For anyone responding before NHS clinicians arrive (bystanders, police, fire, voluntary responders): ^[6]

• Walking: yes gives P3.
• Severe bleeding: yes gives P1 after pressure, tourniquet or packing.
• Talking: yes; if there is a penetrating injury (front or back) this is P1, otherwise P2.
• Breathing: open the airway if able; a casualty who then breathes and is placed in the recovery position is P1. A casualty not breathing receives CPR if resources allow.

For all NHS responders; a single tool for adults and children: ^[5]

• Catastrophic bleeding: yes, after pressure dressing, tourniquet or haemostatic packing, gives P1.
• Walking: yes gives P3.
• Not breathing: open the airway; dead. In children under 12 who are not breathing, if resources allow give 5 rescue breaths first when there has been submersion, immersion or smoke inhalation. ^[5]
• Responding to voice: no gives P1 after placing in the recovery position.
• Aged over 2 years: no gives P1. ^[5]
• Breathing rate 12 to 23 per minute: no gives P1. ^[5]
• Heart rate: no gives P2.

The tool also sets out the METHANE model and provides boxes to number casualties in each priority, P1 to P3 and dead, from 1 to 19. ^[5]

The emergency planning route is: control rooms usually notice unusual activity and notify the on-call incident manager; the ambulance, police or fire service requests escalation. A hospital may self-declare a standby based on an unexplained surge of casualties or on reliable news of an emerging incident. ^[4]

On a major incident standby, an NHS hospital activates departments in parallel: ^[4]

• Emergency department: call in staff, locate pre-printed major incident registration documents, and set up an external or ambulance-bay triage station.
• Critical care and wards: identify patients suitable for step-down, prepare a discharge ward, and hold trauma beds.
• Theatres: consider suspending non-essential surgery, set up a theatre coordination point, and hold a clinical coordination meeting.
• Imaging: move non-urgent cases away from the emergency department CT scanner; urgent cases stay in the emergency department.
• Resuscitation: assemble triage teams (ideally one doctor and one nurse per casualty), name roles, set checkpoints and move spare trolleys to the department. ^[4]

Casualties are expected to be a mix of about 25% P1 (immediate life-saving interventions), 25% P2 (interventions that can wait a short while) and 50% P3 (walking wounded or minor injuries). A major trauma centre should expect mainly P1 casualties, a trauma unit mainly P2, and other facilities P3, but a mix should be planned for because transfers between sites may not be possible in the first 24 hours. ^[4]

Ideally, P3 walking wounded patients should not enter the emergency department but are directed to a separate area, given a clinic appointment or directed to another treatment facility. ^[4] A hospital should agree a pre-determined patient dispersal (casualty regulation) plan, showing where casualties go and how many each site accepts in the first hour. ^[4]

Children under 12, or those within the paediatric triage tape, are directed to a paediatric major trauma centre, with priority for the smallest children. Casualties over 12 go to an adult major trauma centre or trauma unit. ^[4]

Careful attention is needed to avoid a reverse flow of minor casualties arriving in the resuscitation area; decontamination, if needed, should occur before entry, but life-saving interventions are not delayed for formal decontamination. ^[4]

Once a major incident is declared, hospitals update and receive METHANE information, run the clinical impact assessment call and complete patient summary sheets, manage theatre and critical care, and protect the psychosocial care of casualties and staff. The Newcastle principle holds that the guidelines are written for the occasional trauma team: a trauma unit that has to accept a P1 or deteriorating P2 patient during a surge. ^[4]

The hospital guidelines blend pre-hospital and military trauma practice for civilian NHS use: ^[4]

• Catastrophic haemorrhage control comes first (jumping the usual ABC sequence if needed), using direct pressure, wound packing or tourniquet for compressible bleeding.
• Airway with spinal protection as needed; definitive airway for inability to maintain or protect the airway.
• Breathing: treat tension and open pneumothorax, massive haemothorax and flail chest.
• Circulation: two large-bore intravenous lines, permissive hypotension (systolic target around 80 to 90 mm Hg where there is no head injury, or about 90 mm Hg by other guidance), balanced blood products and, within 3 hours, tranexamic acid.
• Disability: Glasgow Coma Scale, pupils and glucose.
• Exposure and warming, because hypothermia below 34 degrees Celsius worsens coagulopathy.

Debrief formally; hot and cold debriefs are held, a post-incident report is produced covering the nature of the incident, agency involvement, strategic management actions and a chronology, and care aftercare (bereavement, psychological support, rehabilitation). Hospitals should build these into their emergency plan before an event occurs. ^[4]

A CBRN or hazardous-materials incident is a major incident in which the threat to casualties and to staff comes from the substance rather than the trauma alone. The characteristics and priorities differ by exposure type; chemical exposures usually give more acute symptoms (minutes to hours), whereas biological and radiological exposures may be delayed and less obvious. ^[4]

Emergency personnel should be alert to the safety triggers: ^[4]

• Step 1: one person incapacitated with no obvious reason; manage with standard protocols and standard precautions.
• Step 2: two people incapacitated with no obvious reason; manage with caution using standard protocols and personal protective equipment.
• Step 3: three or more people in close proximity, incapacitated with no obvious reason; manage in a safe, well-ventilated area, considering disrobing before handover. ^[4]

The PLUS actions: evacuate (remove the patient, other patients or non-essential staff where needed), communicate (tell staff, management and/or emergency services), disrobe (at minimum remove clothing from P1 casualties) and decontaminate (appropriate type and extent, but life-saving interventions are performed first where practicable). ^[4]

Unusual pointers include mass eye or airway symptoms, non-thermal burns, an unusual smell or mist, dead animals, unexpected laboratory findings, or symptoms in staff. ^[4]

CBRN casualties are managed on the general trauma principles, modified by contamination. Priorities depend on exposure, the presence of contamination and the contagion hazard. Assistance is obtained quickly: in the UK, via the Emergency Co-Ordinated Scientific Advice system (ECOSA, 0300 3033 493) and the National Poisons Information Service (0344 892 0111). Comprehensive guidance is available from Public Health England (now the UK Health Security Agency). ^[4]

Where formal decontamination cannot be achieved quickly, life-saving haemorrhage control, airway opening or needle decompression are still done before or during it; do not let decontamination delay resuscitation. ^[4]

Nerve agents are organophosphorus compounds producing a cholinergic toxidrome. A triage screen (CRESS) classifies casualties by signs into three priority groups: ^[4]

• P1 (severe): unconscious, convulsing, respiratory distress or arrest, profound bradycardia (under 40 beats per minute), cyanosis, not walking. ^[4]
• P2 (moderate): excessive secretions, confusion, not obeying commands, wheezing, incontinence.
• P3 (mild): walking, with pinpoint pupils, dimmed vision or eye pain.

Management is symptom-directed: antimuscarinic (atropine), oxime (pralidoxime) and benzodiazepine anticonvulsants, with a ventilation strategy suited to high airway pressures. ^[4]

The UK routine approach to radiation emergencies uses a similar principle: triage is by signs and symptoms and may be performed as "walking, waving, still", since there is no equipment to measure internal contamination at the scene. ^[4] Biological risks require isolation, identification and infection-control precautions. Across all hazards, protecting the responder (appropriate personal protective equipment, distance, time and shielding) and accurate information (METHANE) are as important as treating the casualty. ^[4]

The World Health Organization Health Emergency and Disaster Risk Management Framework (2019, 31 pages) treats emergencies as a whole-system issue: prevention, preparedness, readiness, response and recovery across sectors, with communities at the centre and particular attention to the most vulnerable. ^[7]

Its scale is sobering: every year more than 170 million people are affected by conflict and another 190 million by disasters, with impacts on health and on universal health coverage. ^[7]

WHO mass casualty guidance describes common gaps: many countries have not yet developed mass casualty management plans, and communities are often left to prepare without guidance from higher levels. ^[7] The preparedness actions that follow are practical translations of that: plan, train, test.

• A major incident is any event that needs special arrangements; the first priority of triage is the greatest good for the greatest number. ^[4]
• Standby can be external or self-declared on the basis of a surge or credible news.
• START sorts adults in around 30 to 60 seconds by walk, breathe, pulse and command; the 1996 Benson change substituted radial pulse for capillary refill; only airway opening and direct-pressure haemorrhage control are allowed. ^[1][2]
• SALT is an all-hazards algorithm with a sort stage, broader permitted actions and the same four colour categories; its CBRN performance is uncertain. ^[1][3]
• Reverse triage and burn and paediatric systems adapt triage to specific populations. ^[1]
• METHANE carries Major incident, Exact location, Type, Hazards, Access, Number of casualties and Emergency services needed. ^[4][5]
• Hospital response: standby activation, external triage, separate P3 flow, planned casualty regulation, triage categories, decontamination as required and debrief. ^[4]
• Expected mix of casualties: roughly 25% P1, 25% P2, 50% P3. ^[4]
• NHS Ten Second Triage and MITT (2023) provide P1/P2/P3 and breathing checks; MITT derives from MPTT-24 with reported better sensitivity. ^[5][6]
• CBRN: STEP 1-2-3 PLUS for safety, life-saving care before formal decontamination, nerve-agent triage into P1/P2/P3 and antimuscarinic/oxime/anticonvulsant therapy. ^[4]
• WHO EDRM (2019) frames health-sector preparedness as prevention, preparedness, readiness, response and recovery across all hazards. ^[7]

• Trauma: primary survey and initial trauma assessment
• Haemorrhagic shock and damage control resuscitation
• Mass casualty and trauma triage (START, Sieve, TST, MITT)
• Chemical incident and nerve agent poisoning
• Decontamination and personal protective equipment in emergency care
• NHS Emergency Preparedness, Resilience and Response (EPRR) framework