Triage, derived from a French word meaning "to sort", originated in military medicine, but is widely used in medical situations where there is more demand for resources than can immediately be met. In the general practice of emergency medicine, patients presenting at an emergency room usually receive basic triage from a nurse, who determines who is in need of immediate care, urgent care, and care when it is available; patients are not taken to physicians on a first-come-first-served basis.
As opposed to general emergency care, triage takes on special significance in multiple casualty incidents and mass casualty incidents. These, of course, are common in battlefield situations, where the practice came into use. The goal of triage is to optimize several different factors: the severity of a patient's condition, the resources that are available, the probability that a given set of resources will produce a desirable outcome, and the overall demand on resources.
Triage, for multiple and mass casualty incidents that are within the purview of one emergency response system, often begins in the field.
Until resources start being overwhelmed and an incident changes from multiple to mass casualty, there are three main categories:
- Victims with life-threatening injuries that must be treated as soon as possible, such as in acute respiratory distress from pneumothorax or a toxic chemical
- Victims in need of definitive treatment, but who can tolerate some delay, such as fractures without hemorrhage
- Victims that may need minor care; in the military, or other environments where there are many basic-level providers, this may be called "buddy care" or "self-care".
Depending on policy, including legal, ethical, and operational considerations, there may be diversion of frightened but healthy people, and those that are clearly dead. Guidelines for determining death, in the field, vary with the training of the responder and the operational environment; it takes little training to determine that decapitation is incompatible with life, and more to attempt to reestablish breathing with various fast resuscitation measures. Mechanism of injury plays an important part, such as blunt trauma from blast. 
In less critical situations, there is more variation on the authority of paramedical personnel to declare death under field conditions. Decapitation remains a criterion, but, while a pulseless and nonbreathing victim would immediately be declared dead under mass casualty condition, more evaluation might be done if there are no other victims that can clearly be helped. For example, an increasingly large number of systems recognize that a pulseless victim of blunt chest trauma has essentially no chance of survival, while a victim of penetrating chest trauma may have some survival chance if they can be transported to a facility capable of certain immediate (i.e., as in the emergency room) surgical interventions.
|Category||Field criteria||Treatment facility criteria|
|1, Immediate, "Red Tag"||Immediately life-threatening conditions; apply available stabilization and transport. Airway obstruction; Flail chest; Tension pneumothorax; Hemorrhage||Immediately life-threatening conditions that available resources can treat effectively. Take steps necessary to prevent death in a short time (e.g., airway control, administer antidotes to suspected chemicals); highest priority for surgery or other definitive care|
|2, Urgent, "Yellow Tag"||Stabilize with minimal essential measures (e.g., establish IV access and maintain permissive hypotension in appropriate trauma victims), and transport. Fractures;
Soft tissue injuries without active hemorrhage; Head trauma;Open abdominal wounds
|Monitor, obtain imaging when necessary (typical for orthopedic injuries that will need surgery), definitive treatment after category 1 patients are treated|
|3, Deferred or Minimal, "Green Tag"||Primarily transport, pain control. Minor abrasions, burns, lacerations; Moderate anxiety; Open/closed fractures without complications ||Comfort measures while awaiting treatment|
|4, Expectant, "Black Tag"||Meet criteria of death or impending death. Do not transport. Marginal but responsive victims (e.g., breathing but possible lethal radiation exposure); Massive head or spinal injury; Third degree burns > 70% of body surface area; Injuries incompatible with lifeSome authorities say black tag is applicable only under combat conditions, but it is hard to draw the line between formal combat and major disasters or terrorist incidents.||After additional evaluation, determined to have no chance of survival under any circumstances (e.g., acute radiation syndrome of the central nervous system presentation), or no chance of survival with available resources (e.g., major burns or brain injury). Comfort measures only|
Specialized rating systems
Emergency and critical care medicine needs to use triage in non-disaster situations as events in which only minimal triage criteria are practical. Specialized methods have been developed for certain types of patients, differentiating, for example, between medical and trauma patients. One of the controversies in trauma triage is the extent to which "mechanism of injury" should be considered: is the victim of an automobile accident believed been at some value of high speed, or a gunshot wound to a certain anatomic area, to be triaged as urgent regardless of their immediate clinical presentation?
Triage for acute radiation syndrome involves both mechanism of radiation injury as well as immediate clinical presentation. Decisions may be especially difficult when the patient seems only mildly ill, but there is objective measurement data that shows a non-survivable radiation dose was received.
- Lockey, A S (2002), "Recognition of death and termination of cardiac resuscitation attempts by UK ambulance personnel", Emerg Med J 19: 345-347
- Moore, Brendan (2006), "Blast Injuries - A Prehospital Perspective", Journal of emergency prehospital care
- Allen, Robert C., ed. (Second Edition (28 February, 2001)), Parrescue Medication and Procedure Handbook, U.S. Air Force Pararescue
- South African Triage Group, SATS (South African Triage Scale)