Field triage guidelines. Knowledge of injury, mechanism, and existing co-morbid factors are keys to optimal trauma triage. Unfortunately, no single factor will guarantee triage success. The following have been developed by the Centers for Disease Control and Prevention (Table 9-1):

Field triage scoring. Several trauma-scoring techniques determine the severity of injury of trauma victims both in the hospital and in the field. Examples include the Trauma Score, CRAMS Scale, Prehospital Index, and Trauma Triage Rule. Accurate trauma scoring is dependent on diagnostic skills and the availability of adjunctive testing, and is limited by field conditions, patient intoxication, and compensatory physiologic mechanisms masking major injuries. Trauma-scoring systems typically look at combinations of the following:

The first EMS personnel to arrive on scene initiate mass casualty triage. Providers first ensure scene safety and relay basic information regarding the incident to dispatchers, so additional resources can be mobilized and hazards mitigated. The responsibility for patient triage is assigned to more experienced personnel when they arrive. Field triage works best when victims are limited to a small geographic area. Large disaster sites (such as earthquakes and floods) or disasters with geographically distinct areas (such as either side of a train crash, when mobility between and access to the two sides is limited by the wreckage) can require multiple triage sites.

Principles. While it is generally taught that the most critically injured patients are transported first, empiric data are lacking to support this principle. Triage is a continuous process, with frequent reassessment of patient status and resources. Patients are typically re-triaged on arrival at the hospital.

Simple triage and rapid treatment (START) is the most commonly used mass casualty triage system in the United States. Patients who are ambulatory are first removed from the area. Next, patients are classified as “expectant” if obviously dead or if not breathing after one attempt to reposition the airway. Remaining patients are categorized as “immediate” or “delayed,” on the basis of the evaluation of respiratory rate, perfusion, and mental status. An abnormality

in any one parameter places the victim in the “immediate” category (Table 9-2).

Triage tags are often used to identify needs in both large and small multi-victim incidents.

Over-triage (false positives) occurs when a patient who does not require a trauma center or high level of immediate care is assigned to and transported to a trauma center. When resources are not constrained, this results in some degree of wasted resources if activation of the trauma team occurs unnecessarily. In a mass casualty situation, over-triage may limit the ability of a trauma center to provide optimal care for those who need it.

Under-triage (false negatives) occurs when a patient who may benefit from trauma center/higher level of care is transported to a setting with fewer resources. This can affect ultimate outcomes; in a mass casualty incident, under-triage may be unavoidable as trauma centers become saturated.

While it is commonly stated that 50% over-triage is acceptable to achieve 10% under-triage, there are no outcome data to support this supposition.

Likelihood of survival. The research on this topic often includes a mixture of clinical conditions, making interpretation difficult. A few general guidelines can be gleaned from the available data.

Injury obviously incompatible with life (e.g., decapitation, incineration)

Absent signs of life (no respiratory effort, no pupillary response or eye movement, no response to deep pain) and ECG rhythm of asystole

Documented, untreated pulselessness and apnea for 15 minutes (e.g., prolonged entrapment, hazardous scene) in a normothermic patient

Rigor mortis or dependent lividity

Transport time to an ED or trauma center of more than 15 minutes after the onset of cardiopulmonary arrest

Electrical shocks or lightning. Since arrest is usually caused by a cardiac dysrhythmia and may be reversible, aggressive resuscitation should be attempted. In cases of multiple casualties from an electrical incident, defibrillation of those in ventricular fibrillation or pulseless ventricular tachycardia arrest should be given first priority.

Drowning or hanging. Arrest is usually caused by asphyxia in these situations. Although appropriate trauma care, such as spinal immobilization, should be instituted, the decision to resuscitate can be based on criteria for “medical” arrests. Hypothermia should be considered in drowning victims.

Hypothermia. The presence of hypothermia (core temperature below 35°C) can result from or lead to a traumatic event. Hypothermia can make it difficult to detect signs of life. Patients who are severely hypothermic should generally undergo active core rewarming before cessation of resuscitative efforts unless injuries are clearly incompatible with life. Refer to Chapter 43 for more details on this illness and treatment.

Arrest secondary to medical cause. It can be a challenge to recognize patients who may have suffered trauma or cardiac arrest because of a medical condition, such as the driver of an automobile who develops ventricular fibrillation with a resultant crash. Unless evidence suggests a fatal injury, a patient whose mechanism of injury does not correlate with the clinical condition should typically undergo resuscitative efforts similar to any other non-traumatic arrest patient. Following return of spontaneous circulation, these patients should undergo a complete trauma evaluation to exclude further injury followed by treatment of the medical condition that precipitated the arrest.

At the scene. Time on scene (excluding extrication) should be as short as possible—often targeted for 10 minutes maximum, absent extrication concerns or other operational delays.