Community Medicine — Disaster and Mass Casualty Management, NMC MBBS licence examination syllabus (Nepal Medical Council).
Disaster and Mass Casualty Management
Everything you have been taught about prioritising the sickest patient stops applying the moment casualties exceed capacity.
The defining feature of a mass casualty situation is not that many people are hurt. It is that the need exceeds what is available — not enough staff, not enough theatres, not enough blood, not enough time.
That single fact changes the ethical arithmetic of medicine, and it is the reason this topic is taught separately rather than as an extension of emergency care.
The rule that reverses
In ordinary practice the sickest patient is treated first. That works because resources are adequate: treating the critically ill patient does not prevent anyone else from being treated.
When resources are inadequate, that principle produces the worst outcome. The most severely injured patient may absorb an entire operating theatre, the surgical team and the available blood — and still die — while five people who could have been saved with far less deteriorate untreated.
So the governing principle becomes the greatest number who can be saved. This means a patient who would receive full resuscitation on a normal day may instead receive pain relief and comfort. That is not abandonment and it is not a judgement about their worth — it is arithmetic, applied under conditions nobody would choose.
Why does this need saying explicitly? Because it runs against every clinical instinct that training builds, and it is psychologically very hard to do. Doctors who have not thought about it in advance default to treating the patient in front of them, which is exactly the failure mode described below.
The four groups
Triage sorts casualties along two axes at once: how urgent and how salvageable.
Immediate. Life-threatening problems that a short intervention can fix — an obstructed airway, compressible haemorrhage. These are the highest priority because the return on effort is enormous.
Urgent. Serious injuries that will deteriorate without treatment, but not within the next several minutes. They can safely wait while the immediate group is dealt with.
Delayed. The walking wounded. Frequently the largest group, they can wait a long time — and some of them can help, carrying stretchers, comforting others, or applying pressure to wounds.
Expectant. Injuries not survivable with the resources available. The crucial qualifier is "with the resources available": the same injury might be survivable in a well-staffed hospital on an ordinary day.
Expectant does not mean abandoned. These patients receive analgesia, comfort, and where possible someone to stay with them. Failing to provide that is a failure of care, not an unavoidable consequence of triage.
💡 Exam angle: this chapter gives no specific physiological cut-offs or colour codes, deliberately. Triage systems differ between countries and institutions, and applying one system's numbers under another's protocol causes miscategorisation. Learn the protocol used where you work. What examiners test — and what transfers between systems — is the reasoning: urgency against salvageability, and the reversal of the usual priority.
Triage is repeated, not decided once
A triage category is a snapshot of one patient at one moment with one set of available resources. All three change.
Patients move in both directions. Someone initially categorised as delayed may have a slowly expanding haematoma and deteriorate. And an expectant patient may become salvageable when a surgical team arrives or a helicopter lands — which is why the expectant group must be reassessed rather than written off.
The commonest operational failure is simple and human: the triaging clinician stops to treat someone. The moment they do, nobody is sorting the remaining casualties, and the whole system reverts to first-come-first-served. Triage should be done by the most senior available clinician precisely because that judgement is difficult — and that person must keep moving.
What actually kills after the first week
Public attention focuses on the rescue phase, but in most disasters the deaths from crush injury and trauma are concentrated in the first hours and days. What follows is a public health emergency, not a surgical one.
Displacement is the driver. People are crowded into camps or temporary shelters with inadequate clean water, poor sanitation and no privacy — conditions that produce diarrhoeal disease, respiratory infection, measles outbreaks, and malnutrition among children and the elderly.
The interventions that save the most lives in this phase are correspondingly unglamorous:
Water and sanitation above everything else.
Shelter and food.
Measles vaccination, because crowding plus unvaccinated children produces outbreaks quickly, and measles kills malnourished children efficiently.
Disease surveillance, so an outbreak is detected while it is still small.
And chronic disease does not pause for a disaster. People with diabetes, epilepsy, hypertension, tuberculosis and HIV lose access to medication when pharmacies are destroyed and clinics close. Deaths from interrupted treatment are entirely preventable and are routinely overlooked in favour of visible trauma.
💡 A persistent myth worth correcting, and a favourite examination point: dead bodies do not cause epidemics. Victims of trauma were not infectious at the moment of death, and the organisms of decomposition are not epidemic pathogens. The urgency around mass burial is driven by distress and by belief rather than by infection risk — and rushed anonymous burial causes lasting harm, because families cannot identify their dead and legal processes such as inheritance and death registration become impossible. Bodies should be handled with dignity and identified where possible. The epidemic risk lies with the living survivors' water, sanitation and crowding.
Preparedness
The quality of a disaster response is largely fixed before the disaster happens.
A plan nobody has rehearsed is not a plan. Written procedures filed in an office fail on the day, because staff do not know their own role, cannot find equipment, and have never practised working with people they do not normally work with. Rehearsal is what converts a document into a capability.
The hospital has to survive the event. A hospital that collapses in the earthquake, floods, or loses power and water converts a disaster into a catastrophe — it removes the response capacity at the moment of maximum need. Structural safety of health facilities is a public health intervention.
Command and communication. Someone must be in charge, everyone must know who, and there must be a plan for when the phones stop working. Confusion about who is deciding wastes the early hours, which are the ones that matter.
One fact reframes the whole subject: most rescues are performed by local people in the first hours, using their hands and whatever is nearby, long before any organised team arrives. Community preparedness and basic first aid training therefore save more lives than the arrival of external specialists — which is an argument for investing in the population rather than only in the hospital.
Putting it together
A mass casualty event is defined by need exceeding capacity, and that reverses the usual priority to the greatest number who can be saved.
Four groups: immediate, urgent, delayed, expectant — and expectant means comfort care, never abandonment.
Re-triage constantly, and do not let the person triaging stop to treat.
After the first week the killers are water, sanitation, crowding and interrupted chronic treatment, not trauma.
Dead bodies do not cause epidemics. The living survivors' conditions do.
Rehearsed plans, a surviving hospital, clear command — and local people who can help in the first hour.
No triage cut-offs, colour codes or event statistics are quoted here. Triage protocols differ between institutions and must be learned locally — applying another system's numbers causes miscategorisation.
Syllabus points
Why the usual clinical priority reverses
The four triage groups; what expectant means
Re-triage; why the triaging clinician must not stop
The second wave — water, sanitation, crowding, measles
Interrupted chronic disease treatment
Dead bodies do not cause epidemics
Rehearsed plans, a surviving hospital, clear command
Local people perform most rescues
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