Figure 1.

Reactive critical care response to mass casualty event. The figure provides an integrated overview of the reactive response to an event producing critically ill or injured individuals. A reactive response is required when there is little or no pre-event warning, thus limiting the ability of the system for augmentation prior to the surge. Working from left to right in the diagram. Trigger thresholds: these represent points when criteria are met for activation of various tools such as mass critical care (MCC) and triage. Tiers: this graphic component of the diagram describes the tiers of the response. Based on the magnitude of the event, higher tiers will be activated. Graphical figures illustrate hospitals, jurisdictions (ie, a city), states, and a nation. The circle and slash denotes that the associated resource is overwhelmed. From bottom up: Row 1: Individual facility response occurs either early in an event as the first receiving hospitals are impacted or in events with smaller magnitudes. Row 2: Health-care coalition response occurs when several local area hospitals are overwhelmed. Row 3: Local jurisdictional response occurs when the resources of an entire jurisdiction are drawn on due to direct impact or via mutual aid responses. Row 4: State responses are activated to support events occurring in multiple jurisdictions or if the entire state is impacted. Row 5: Interstate regional responses draw on the resources of neighboring states as entire states are overwhelmed. Row 6: Federal responses are required for large events usually involving a wide geographic area. Response: At tier 1 usual surge strategies are employed including activation of mutual aid agreements with neighboring hospitals. At tiers 2 to 4, as it is recognized that multiple hospitals or jurisdictions are overwhelmed and due to the sudden nature of the event there is insufficient time to decant patients or effectively augment the response in a timely manner, reactive mass critical care strategies may be employed temporarily until either of these are accomplished or 24 h has elapsed, at which time permission may be obtained from the appropriate authorities to continue mass critical care. Should a sudden event overwhelm resources to the tier 5 or tier 6 level, mass critical care will likely be required. Resource allocation strategies will be employed as part of mass critical care strategies in tiers 1 to 5, but critical care triage protocols should only be employed if resources are overwhelmed beyond the tier 5 level. Casualties: This is an illustrative graphic of critically ill casualties generated by an event. The impact of an event is not solely dependant on the absolute number of casualties but also the specific medical needs of the casualties and the available resources.