A Mass Casualty Incident (MCI) occurs when the number and severity of injuries overwhelm the immediate ability of local emergency medical services (EMS) to deliver comprehensive care. Unlike typical emergencies, an MCI requires a systematic delay in transport to organize the chaos and prioritize resource allocation. The immediate goal is to establish order and determine who requires the most urgent attention from the limited resources available. This systematic approach ensures that transport, when it begins, is efficient and targeted toward maximizing the number of survivors.
Establishing Patient Priority Through Triage
The initiation of transport is contingent upon the completion, or near completion, of the initial rapid assessment process known as triage. Triage is a sorting method used to categorize patients based on their immediate need for treatment and their likelihood of survival. The most common system is Simple Triage and Rapid Treatment (START), which allows first responders to quickly assess patients in 30 seconds or less.
This process focuses on basic physiological indicators like respiration, perfusion, and mental status, rather than complex medical procedures. The outcome of this assessment is the assignment of a color-coded priority tag to each patient. These tags include Immediate (Red), Delayed (Yellow), Minor (Green), and Deceased/Expectant (Black).
The physical movement of patients toward the transport area only starts once the Triage Unit Leader provides the Incident Command with a reliable count of the highest-priority patients. This primary assessment determines the true scope of the incident’s demands. The tags serve as the foundation for all subsequent treatment and transport decisions.
The Command Decision to Initiate Movement
The decision to begin transport is governed by the established framework of the Incident Command System (ICS). Transport is a deliberate, authorized step, not one that starts simply when the first ambulance arrives. The Incident Commander leads the overall management of the incident, overseeing all operational elements, including the medical response.
A Transportation Unit Leader (TL) must be established under the ICS structure to manage all patient movement logistics. The TL’s first action is to secure a safe and functional Ambulance Staging Area for incoming transport vehicles. The TL must also confirm open communication with receiving hospitals to understand their capacity and capabilities.
Transport is authorized when the Triage Unit Leader reports the total number of patients, especially Immediate (Red) and Delayed (Yellow) categories, to the Command Post. Once the TL confirms the readiness of the loading zone and the receiving hospitals, the Command Post authorizes the movement of patients from the Treatment Area. This procedural trigger ensures patients are moved only when the system is ready to receive them.
Sequencing Transport by Priority Category
Once the command decision is made, the sequence of transport strictly follows the priority categories assigned during triage. The goal is to move the highest-priority patients first to maximize their chances of survival. Immediate (Red tag) patients, who have life-threatening injuries but a high potential for survival with rapid intervention, are loaded onto ambulances first.
Following the departure of the Immediate patients, the Delayed (Yellow tag) patients are prepared for transport. These individuals have serious injuries that are not immediately life-threatening, meaning their medical status is not expected to deteriorate significantly over several hours. This sequencing ensures that resources are focused on the most compromised patients first.
Finally, the Minor (Green tag) patients, often referred to as the walking wounded, are transported. These individuals have minor injuries and can often be moved in larger groups, such as by bus, to a dedicated medical facility. This structured, sequential approach is foundational to effective MCI management.
External Factors Influencing Transport Timing
Even after procedural approval from the Command Post, transport timing is influenced by external and logistical realities. The most significant factor is the availability and arrival time of transport assets, such as ground ambulances and air medical helicopters. Delays in vehicle deployment can substantially prolong the overall pre-hospital time for all patients.
The physical environment of the incident scene, including its accessibility and safety profile, dictates when and how transport can begin. Challenging incident locations or ongoing safety concerns can lead to pre-hospital time delays of two hours or more. The capacity of regional hospitals to accept specific patient types, especially trauma patients, also acts as a constraint.
The Transportation Unit Leader must communicate with a Medical Communications Coordinator to manage patient distribution. This ensures that hospitals are not overwhelmed by a sudden surge of patients. Coordinating patient destinations based on injury type and hospital capability is a continuous process that affects transport timing. These logistical barriers often determine the practical moment of transport initiation.