ArticlesReduction in critical mortality in urban mass casualty incidents: analysis of triage, surge, and resource use after the London bombings on July 7, 2005
Introduction
The multiple bomb explosions in London on July 7, 2005, resulted in the largest mass casualty event in the UK since World War 2. By contrast with multiple casualty incidents, a mass casualty event taxes emergency systems, hospitals, and community infrastructure, and exceeds the capability of available resources to provide optimum trauma care.1 Mass casualty events such as the New York World Trade Center attack in 20012 and the Madrid commuter train bombings in 20043 have high numbers of injured casualties and test disaster contingency plans to the full.
As modern warfare shifts towards civilian arenas, millions of people are now living with the threat of terrorism, while around the world the number of natural and man-made disasters continues to rise.4 Emergency service, hospital, local, and regional disaster plans are being revised to respond to these new and increasingly likely events. Much of this planning is done in a relative vacuum of information detailing how and when different parts of a trauma system are tested by the resource consumption of casualty surge.
The two fundamental aims of a disaster response are rapid evacuation of all casualties from a hazardous incident scene and to reduce the mortality of critically injured patients.1 Rapid evacuation of all casualties is vital where there is the potential for structural collapse or secondary explosive devices. However, reducing critical injury mortality needs careful assessment to identify the severely injured patients among the large numbers of non-critical casualties. Overtriage—assigning non-critically injured casualties to a high priority for early evacuation and treatment—inappropriately assigns constrained resources and impairs the management of the critically injured.5 Studies of previous terrorist bombing incidents have identified a linear relation between the over-triage rate and critical mortality.6 Thus there are conflicting priorities between the requirements for rapid scene clearance and reducing overtriage. Scene clearance should therefore be highly organised and efficient to optimise casualty triage and survival.
Rapid scene clearance creates a surge in the rate that casualties arrive at receiving institutions. A fundamental issue in mass casualty care is not simply the number of patients that need treatment, but also the rate at which they arrive and use available resources. The ability to maintain standards of trauma care is reduced by this casualty surge, and the ability to provide high-level trauma care under these circumstances is the surge capacity.7
We describe how critical mortality in mass casualty events can be reduced, despite a high scene over-triage rate, by the efficient management of surge at every stage of a disaster response. This study therefore analyses the prehospital and in-hospital response to this mass casualty event to identify the critical mortality and the over-triage rate. We then analyse surge by describing patient flow and resource use at key stages in the disaster response. Specifically, we examined the emergency department, radiology, blood bank, operating rooms, and critical care areas. We then identify system processes that optimise use of resources and reduce critical mortality in the face of maximum surge and high over-triage rates.
Section snippets
Methods
London's major incident plan is developed and organised by the London Emergency Services Liaison Panel.8 A major incident can be declared by any member of the emergency services, either on-scene or in the control room. Response command and control is organised around a Gold (strategic), Silver (tactical), and Bronze (operational) structure.9 Inter-agency discussions at Gold level escalate a local incident to London-wide status, coordinated from a dedicated Gold control operations centre. Gold
Results
At 0850 h on Thursday July 7, 2005, three bombs exploded on trains at three different locations on the London Underground system. A fourth bomb exploded on a double-decker bus at 0947 h. Edgware Road station was the first site to be declared a major incident at 0912 h followed by King's Cross station at 0919 h, Aldgate station at 0924 h, and Tavistock Square at 0957 h. Initial reports were confused as to the nature and number of explosions, not least because of casualties emerging from stations
Discussion
This study presents a detailed analysis of critical mortality, casualty flow, and the medical response to an urban mass casualty event. We identified a relatively low critical mortality and showed how triage errors and surge can be reduced by trained, experienced decision-makers working in their usual environments. Finally, we showed how damage-control principles can be applied to a mass casualty response to reduce resource use and optimse surge capacity.
In assessing the effectiveness of a
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