Trauma, 7th Ed.

CHAPTER 8. Disaster and Mass Casualty

Eric R. Frykberg and William P. Schecter

INTRODUCTION

The term disaster is subject to a variety of interpretations and misperceptions that typically relate to one’s background and experience, but there are specific characteristics on which most would agree. An essential feature of a disaster involves a major disruption of the infrastructure of a community or geographic region and its inhabitants. Another is that the magnitude of destruction exceeds that of routine emergency situations to such an extent that the response to it must be entirely different in order to restore some semblance of order and normalcy. Approaching a disaster with the mindset of simply doing more of the same, using the same methods as routine emergencies, is generally doomed to failure and tends to extend rather than curtail the adverse consequences.1

True disasters are rare. Very few events in a century result in more than 1,000 casualties, and only about 10–15 events each year throughout the world result in more than 40 casualties.2 Because they are rare, as well as unpredictable, random, sudden, and unexpected, their successful management requires established and well-rehearsed plans that anticipate necessary consequences, procedures, and needs.24

The feature that best distinguishes the medical response to a disaster from the routine medical care of patients is that resources are overwhelmed by the casualty load. The receiving hospital is therefore unable to provide each casualty with the optimal level of care that is standard in routine medical management.5,6 External assistance is necessary to manage the event. This has significant impact on the approach to medical care and the associated ethical considerations, as, by definition, the limited resources must be rationed according to who most merits care so as to avoid squandering these resources and leaving many other casualties without care that may be more effectively applied in terms of overall casualty salvage. This means that some casualties who would ordinarily be treated may have to be denied full care for the sake of saving many more. These altered standards of care that must prevail in true disasters tend to be unfamiliar and morally repugnant to health care providers, and they are not taught in medical or nursing schools or residency training. This emphasizes the necessity of education and training in these principles if a medical response is to succeed.7 This response cannot just be more of the same, but an entirely different approach to care. The longer it takes to learn this as a medical response unfolds, the more property and lives will be lost unnecessarily.1

multiple casualty event is one in which hospital resources are strained, but not overwhelmed, by the patient load, as we experience on busy nights in urban trauma centers and emergency rooms. All patients are ultimately fully treated according to our standard principle of the greatest good for each individual, although the costs include extra personnel, financial losses, delays in care, and difficulty in finding beds, operating rooms (ORs), and equipment. A mass casualty event is distinctly different, referring to casualty loads that overwhelm available resources, preventing optimal individual care. This requires a paradigm shift in focus on a new principle of the greatest good for the greatest number. A disaster response must revolve around the population rather than the individual, with all the difficult ethical implications of rationed care.7,8 The average medical provider may never see a true mass casualty disaster in an entire career, which all the more emphasizes the importance of education and training to prepare for them.

CLASSIFICATION OF DISASTERS

Several classification schemes (Table 8-1) have been applied to disasters.3 The number of casualties is often used to define a mass casualty event and its severity, although it is a relative measure that does not necessarily reflect the magnitude of an event. Five victims of a motor vehicle crash could be handled easily at a major urban trauma center, while this could overwhelm a small rural hospital and be seen there as a true mass casualty disaster. Classification according to mechanism, such as tornados, hurricanes, earthquakes, fires, floods, shootings, or bombings, natural or man-made, allows identification of distinct patterns of damage, injury, and logistical demands. Classification according to injury type similarly allows distinction of these patterns to facilitate response planning, such as burns, blast injuries, and chemical or radiation poisoning.

TABLE 8-1 Disaster Classification Schemes

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Extent and timing of a disaster may be a useful means of classification in view of the very different types of response required for specific geographic and time course considerations. A closed disaster refers to a single event occurring in a specific location, with a clearly defined scene, such as a building collapse. Closely related to this are finite disasters, which occur within a defined and usually short period of time with a clear beginning and end, such as tornados or terrorist bombings. The response challenges in terms of resources and personnel would be quite different in open disasters occurring over a wide geographic area, such as hurricanes, and in ongoing disasters, in which destruction occurs over a prolonged and uncertain time period, such as aftershocks following an earthquake, disease pandemics, or armed conflicts and wars.

The most useful classification scheme groups events according to the level and extent of response and resources necessary to manage the destruction of people and property. A common system involves three levels of response, from local to regional to statewide, national or international. This tends to work best and is widely used because it corresponds to the most basic disaster characteristic of overwhelmed resources, and magnitude is reflected by the extent of external assistance that is needed.

PLANNING

Plans are nothing. Planning is everything.

Dwight David Eisenhower

The word disaster is derived from the Latin words for “evil star,” suggesting that these events are random and unpredictable acts of God for which anticipation and preparation is futile. In fact, the very rarity and unpredictability of disasters make advance preparations essential for a successful response to occur, as the complexity and very different approaches of such a response tend to be counterintuitive and cannot be cobbled together at the time of the event. Furthermore, there are patterns of property damage, bodily injury, behavior, response elements, and pitfalls that are common to all disasters. Once such patterns can be identified (Fig. 8-1), preparation and planning are entirely possible, and moreover are the most essential factors that lead to a successful outcome in terms of minimizing the loss of infrastructure and lives.4,912

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FIGURE 8-1 Graphic comparison of the range of Injury Severity Scores (ISS) of survivors of the terrorist bombings of the train station in Bologna, Italy, in 1980 and the U.S. Marines barracks in Beirut, Lebanon, in 1983,6,19,63showing the common pattern seen in most disasters of only a minority with critical injuries. (From Frykberg ER. Disaster and mass casualty management. In: Britt LD, ed. Acute Care Surgery. 2007:235, Fig. 16-2, with kind permission of Springer Science+Business Media.)

Disaster planning begins with education. Knowledge of the abundant published reports of past disasters and of basic principles of disaster response is necessary for the formulation of a realistic and workable disaster plan. The plan must be based on valid assumptions derived from actual experience so as to accurately anticipate the most likely injury patterns, resource requirements, human behavior, and threats.13Without this knowledge, plans tend to be based on imagination rather than reality. It is common for plans to assume model behavior, rather than incorporate how people actually behave in this setting.2,13

The problems and lessons learned in past disasters serve as an important planning tool that allows the plan to avoid their repetition (Table 8-2), and to thus be more useful in future events. Failure of communications has been the most common and consistent pitfall of disaster responses, due to damage to telephone, cellular phone, and radio infrastructure, and to overloading of that infrastructure by overuse. Communication is the thread that weaves the complex fabric of a disaster response together. Its breakdown impairs the coordination and interoperability of this response. Without redundant systems in place to maintain this interoperability, the response will falter. Another major pitfall of most disaster responses is the uncertainty of who is in charge, which must be designated and understood by all responders in advance to avoid a loss of command and control. Failure of security at the disaster scene and in the hospital increases the dangers to casualties, responders, and medical providers. The system of medical care for mass casualties must be workable to optimize their outcomes. The control of volunteers, the worried well, families, and the media is necessary to prevent confusion of roles, misinterpretation of instructions and messages, and mass confusion by these well-meaning but uninformed and untrained entities. Finally, the original disaster plan has consistently been found to be unworkable very early into the response of virtually every reported disaster, demonstrating a widespread failure of valid and effective planning.14

TABLE 8-2 Common Pitfalls in Disaster Response

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Disaster plans and the process of planning must integrate the many multidisciplinary entities that will contribute to the disaster response and work toward the common goal of recovery (Table 8-3). Plans should be developed by the people who will be executing them. The formulation of a plan should begin with an assessment of the most likely threats that may give rise to a disaster event in any given community or region, which is known as a hazards vulnerability analysis (HVA). The plan should then be built around such threats. Examples include radiation leaks from a nearby nuclear reactor, airplane crashes near airports, floods near major bodies of water, frequent clusters of large numbers of people such as in a sports stadium or theme park, and common weather events such as tornados or hurricanes.

TABLE 8-3 Key Stakeholders in Disaster Planning

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Disaster plans should follow an all-hazards approach, which refers to the creation of only one generic plan encompassing those factors common to all disasters. This is far more effective than multiple plans for each specific type of disaster, as these are unlikely to all be read and remembered by responders and providers. A robust all-hazards plan will have the necessary flexibility to adapt to the unique challenges of each specific event. An example of how to provide such flexibility is to attach appendices to the generic plan for such categories as burns, radiation or chemical poisoning, and blast injuries. The basic premise of all-hazards planning is that all disasters should have the same broad principles of response.4

The planning process is more important than the written plan, which often sits on a shelf unread. The collective interaction of the many different response elements in this process allows all participants to understand the capabilities and needs of each other, and thus how everyone fits into the overall disaster response (see Table 8-3). This provides flexibility and adaptability to the unique exigencies of any specific event, which is independent of the written plan and allows a response to proceed despite an unrealistic written plan. This process helps to prevent the paper plan syndrome, or the false sense of complacency that a written plan may confer even though it is not read or tested.

Once formulated, disaster plans must be tested regularly through both hospital drills of a single facility and community-wide exercises that integrate multiple response elements. These simulations are meant to test the plan for its ability to guide the response to actual events, and should be as realistic as possible in order to confirm its effectiveness and uncover weaknesses that should be improved.4,15

A postevent analysis of all drills and actual disasters is another essential element of disaster planning. This should involve all key participants in the response and should occur within 24–48 hours of the event while memories are fresh. Documentation of all parts of the disaster response should be objectively and comprehensively reviewed to identify those things that worked and those that did not. The plan should then be revised and strengthened accordingly to make it more workable and successful the next time. Disaster planning must be a dynamic process. It is also important to disseminate the lessons learned so as to extend the existing knowledge base.14 Such a postevent critique of the New Orleans response to Hurricane Katrina in 2005 showed a number of weaknesses in the disaster plan despite its thoughtful formulation and testing.16

COMMAND AND CONTROL

In order to coordinate the complex structure of a disaster response, there must be a recognized prevailing authority to exert command and control. The absence of clear authority is one of the most common barriers to a successful disaster response (see Table 8-2), as each of the many participating agencies and personnel tends to believe that it is in charge, and is reluctant to yield its individual missions, agendas, and independence to an overriding command element. This, of course, prevents the smooth coordination and interoperability of all these entities that is necessary to achieve a common goal, as none of these entities have the perspective to appreciate the “big picture.” It is clear that the longer it takes to exert effective command and control of a disaster scene, the longer will chaos, and destruction of property and lives, persist.9,14,17,18

An effective disaster response command structure incorporates three widely recognized command principles. Unity of command refers to a designated hierarchy in which all personnel have specific roles and responsibilities with regard to the common goal. Chain of command refers to the reporting process in this hierarchy, in which each person reports to one supervisor, and no more than five to seven people report to one person (span of control). Unified command refers to the consolidation of all response elements under a single authority who determines the overall mission and objectives toward which all efforts are directed in a coordinated fashion. Deviation from these principles, such as bypassing the chain of command, weakens the structure as a whole by impairing the commander’s situational awareness, and thus the ability to properly execute the mission. This weakness has manifested in a number of major disasters. In New York City on September 11, 2001, no clear authority existed to coordinate the independent actions of multiple response elements following the collapse of the World Trade Center. This same problem was evident following Hurricane Katrina in New Orleans in 2005, and following the earthquake in Haiti on January 12, 2010. The result in these and many similar events was large-scale confusion over the roles of responders, loss and waste of equipment and supplies, lack of enforcement of safety precautions with exposure of responders and medical providers to safety risks, and delays in provision of food, water, shelter, and medical care.

Following a series of wildfires in California in the 1970s, the problem of poor coordination of multiple response units from multiple jurisdictions was identified. The Incident Command System (ICS) was developed as a management tool to address these command and control issues in the setting of major disasters, by incorporating all response elements under a single Incident Commander (IC). ICS is based on functional requirements that are allocated among five major management activities carried out by a general staff—command, planning, logistics, operations, and finance/administration. The operations section is directly responsible for the nuts and bolts of the response, including casualty care, and all other sections support this element. A command staff directly supports the IC with interaction with the media and the public, assurance of safety, and facilitating coordination of all elements, through a Public Information Officer, a Safety Officer, and a Liaison Officer, respectively. The ICS incorporates the three command principles described above to be highly flexible and adaptable to any form of disaster or emergency (Fig. 8-2). Its success and effectiveness is demonstrated by its adoption as the official model for disaster response in the United States and many other countries. All participants in a disaster response must learn this system and their specific role within it.18

FIGURE 8-2 The structure and major functional elements of the Incident Command System.

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TRIAGE

The sorting and prioritization of casualties according to their needs is known as triage. This is generally a minor consideration in routine medical care, where there are essentially unlimited resources and all may be provided optimal treatment. However, in austere environments and in mass casualty events, the process of triage assumes major importance because, by definition, resources are limited, and must therefore be allocated, or rationed, according to the principle of the greatest good for the greatest number. This is a major departure from routine standards of medical care, as necessary considerations of salvageability and resource availability must enter into these decisions.7 The most severely injured casualties with the lowest chance of survival, yet with the greatest resource requirements, may have to be put aside and treated last, if at all, rather than first, in order to conserve the limited resources for the greater number who will most benefit. Rapid identification of this expectant category of casualties provides the best opportunity for maximizing casualty salvage.3,6,9,1922

Image Triage Accuracy

The challenge of triage lies in the very consistent pattern of injury severity found in most mass casualty disasters (see Fig. 8-1), in which a large majority of survivors are not critically injured and therefore do not require immediate care or even hospitalization.6,19,21,23 The rapid identification of that small minority (10–20%) who are critically injured is vitally important in order to direct the limited resources where they are most needed, and not squander them on those not in need. This is the key challenge of health care providers.

The two errors of triage include undertriage, or the inappropriate assignment of critically injured casualties to a delayed, nonurgent category, and overtriage, or the assignment of noncritical casualties to immediate, urgent care. Undertriage is always considered a medical problem that results in preventable mortality, because necessary care is delayed. In routine medical care, overtriage is more of a logistical, economic, and administrative problem, resulting in strained financial, personnel, supply, and equipment resources, but does not impact patient outcomes. However, in a mass casualty setting, when large numbers inundate a hospital all at once, overtriage impairs the ability to detect the critically injured minority who require early lifesaving interventions, and could therefore be as much a threat to casualty survival as undertriage. Hirshberg et al. have provided data to support this contention with a computer modeling study of mass casualty events24 that demonstrates a diminishing capability to optimally care for critical casualties as the rate of overtriage, or influx of noncritical casualties, increases (Fig. 8-3). They have extended this finding with another recent computer model25 showing an improvement in the ability of hospital trauma teams to manage an increasing influx of critically injured mass casualties as triage accuracy increases (Fig. 8-4). That this degradation in care may lead to increased mortality among critically injured mass casualties, as most appropriately measured by the critical mortality rate (CMR), is suggested by a meta-analysis of published data from 14 major terrorist bombing disasters comprising 3,105 casualties (Table 8-4).6,19,23,26 Graphic depiction of these data confirms a highly consistent linear relationship (r = 0.92) between overtriage and CMR (Fig. 8-5).

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FIGURE 8-3 Effect of increasing overtriage (arrival rate of noncritical casualties, non-cm3/h) on hospital capability to optimally care for arriving critical casualties, or surge capacity (cm3/h). (From data in Hirshberg A, Scott BG, Granchi T, et al. How does casualty load affect trauma care in urban bombing incidents? A quantitative analysis. J Trauma. 2005;58:686–695, with permission of Lippincott Williams & Wilkins.)

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FIGURE 8-4 Computer model of mass casualty hospital management showing improving surge capacity (arrival rate of critical casualties) at which trauma teams can provide optimal care (time to saturation of teams) with improving triage accuracy (% correct decisions), with reference surge capacity at 6 critical casualties/h. (From Hirshberg A, et al. Triage and trauma workload in mass casualty: a computer model. J Trauma. 2010;69:1074–1081. Wolters Kluwer Health, Lippincott Williams & Wilkins, with permission.)

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FIGURE 8-5 Relationship of overtriage and critical mortality rate in mass casualties from 14 terrorist bombing events (in black) and 3 nonbombing events (in red), from data in Table 8-4. (Adapted from Frykberg ER. Medical management of disasters and mass casualties from terrorist bombings: how can we cope? J Trauma. 2002;53:201–212, Wolters Kluwer Health, Lippincott Williams & Wilkins, with permission.)

TABLE 8-4 Relation of Overtriage to Critical Mortality in Survivors of 14 Terrorist Bombings and 3 Nonbombing Mass Casualty Events

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This same relationship holds true with the application of data from 3 additional nonbombing mass casualty disasters with a total of 301 surviving casualties—the 1987 Keystone, Colorado, chairlift accident,27the 2003 Station nightclub fire in Rhode Island,12 and the 2007 mass shooting at Virginia Tech.28,29 This overall analysis of 3,406 casualties from 17 disasters (see Table 8-4 and Fig. 8-5) demonstrates that the adverse effect of overtriage is not confined to any one disaster mechanism, but relates to the common pattern of all disasters, regardless of mechanism, in which the inundation of hospitals with a sudden large casualty load interferes with the delivery of urgent medical care.

It is clear that triage accuracy, which involves minimizing both undertriage and overtriage, is essential to the success of a disaster medical response. In fact, it is the one element of a disaster response in which medical providers can directly impact casualty outcomes in the initial aftermath of a disaster. The triage officer who makes these decisions therefore has an important role in this setting. This person must be experienced in the types of injuries that each disaster is likely to cause, and should also be trained in the unique standards that must be applied to mass casualty care in order to optimize triage accuracy, and thus casualty survival. Who should be designated as the triage officer is dependent more on training and experience than on professional background, and it need not even be a physician. It is important to recognize that this position involves only decision making and not treatment, and therefore any physician or surgeon in this role is being removed from casualty care. Available resources must thus impact the decision as to who should be in this position. In some events, nurses or prehospital personnel may best perform this duty. In unconventional disasters, such specialists as infectious disease or public health personnel, radiation biologists, or toxicologists may be the most appropriate triage officer. However, most disasters result in bodily injury, in which setting surgeons and emergency medicine physicians are best in this role because of their experience with the acute care of trauma victims.5,6,9,12,17,21,30 Whoever assumes this role must have the leadership qualities to exert authority and make prompt and firm decisions that will be followed, and must have situational awareness of evolving conditions and resource constraints to make accurate decisions.

Image Triage Decisions

Triage decisions must be rapid as well as accurate in order to move casualties along to accommodate the continuing influx of more casualties. The greater the casualty load, the more rapid must this process be. Therefore, these decisions must be as simple and abbreviated as possible. It should not be surprising that the many complex triage methodology schemes currently in vogue, which require assessment of multiple physiologic and anatomic parameters on each casualty, prove unworkable in true disasters.31 Those who are most experienced in mass casualty triage consistently assert that decisions must derive from no more than a clinical judgment, or gestalt, after a quick look at the victim for a few seconds.5,17,3236 Casualty dispositions must also be simple. In the prehospital sector, all that is necessary is to determine if a casualty is alive or dead, and, if alive, whether hospitalization is warranted or not. Those judged to require hospitalization are then moved on, and at the hospital the decision is made as to entrance or not. Once in the hospital, the basic decision is whether the casualty requires one of the critical resources of OR, intensive care unit (ICU), or not. Further segregation into delayed and minimal categories may be made at this point, but it should be noted that if minimally injured casualties are in the hospital, there was a failure in the triage process to keep them out, as they should not be burdening this critical resource. Those casualties judged as expectant should also be kept out of the hospital to avoid wasting resources. The dead should be recognized and segregated from the living to avoid unnecessary application of resources on their resuscitation.17

What constitutes an expectant casualty cannot be specifically defined in advance, as it will differ for each specific disaster according to such variables as casualty numbers, type and severity of injuries, and available resources. The leaders of the medical care operations should agree on this determination in the earliest phases of the disaster response, when the magnitude and needed resources can best be assessed. Examples of determining factors include the number of mechanical ventilators, availability of electrical power, the presence of toxic contamination, and the number of available ORs and surgeons.9,2022

Triage must be a dynamic process that involves continued reassessment at each successive echelon of care, precisely because injury is dynamic and the status of casualties could change over time. Casualties put aside into delayed or expectant categories should be closely monitored for changes that may warrant reassignment to other levels of urgency. This monitoring is an essential backup mechanism for any triage errors made by the triage officer at any point along the casualty care continuum. Errors must be expected in major mass casualty events, but anticipating them, and instilling flexibility in the system to mitigate their adverse consequences, creates error tolerance. Once the casualty influx subsides, resources can be reevaluated, and expectant and delayed casualties may be reconsidered for immediate treatment or other change in status.5,17

MEDICAL CARE OF CASUALTIES

Image Prehospital Considerations

Disaster responses typically evolve through four phases—chaos, initial reorganization, site clearing, and recovery.17 The initial chaos that characterizes all disaster scenes is brought to order with the arrival of the first responders and their establishment of command and control. Protection of first responders must be the priority at this point, to prevent them from becoming secondary casualties and thus depriving the response of their necessary skills. Responders must adhere to the use of personal protective gear and avoid potentially unstable settings that may result in a “second hit” phenomenon that then kills or disables them, such as leaking gas mains that may later explode, damaged buildings that may later collapse, or second bombs that explode later in terrorist events.6,10,15,17,19 As the command structure becomes organized in the initial reorganization phase, a needs assessment is performed, which guides the mobilization and transport of necessary resources. The initial triage and evacuation of surviving casualties from the scene occurs simultaneously with search and rescue and scene stabilization.

Casualties should not be transported directly to hospitals from the scene, but should go to one or more casualty collection areas (CCAs), where medical providers may further assess and decide on the need for hospitalization. Without the early establishment of a command authority and CCAs, all casualties tend to go, or be sent, to the nearest hospital, which then becomes overwhelmed and unable to render proper care. This is called the geographic effect. It is best avoided by a systematic distribution of casualties among all available hospitals, called leapfrogging, thereby converting the mass casualty event into many more manageable multiple casualty events at each hospital.9,18,34,36,37 This process must be rapid as well as organized, as the time from injury to definitive treatment is a major prognostic factor for casualty survival.6,19

These prehospital phases of response typically play out over a longer period of time following major natural disasters, such as earthquakes, floods, and destructive weather events. In this setting, early medical care is often nonexistent, due to destruction of medical infrastructure, and the opportunity to save critically injured casualties in the initial aftermath is lost. The needs assessment of these scenes is approached from a long-term relief perspective, targeting food, shelter, sanitation, and long-term care of medical problems. In the early phases, surgical interventions most commonly involve the management of complex limb trauma, including crush syndrome, amputations, and wound care. Longer-term issues include definitive limb rehabilitation, wound healing, and rebuilding medical and surgical infrastructure.38

Image Hospital Considerations

The hospital care of the most seriously injured casualties is among the most important elements of a disaster response. Most other response elements revolve around the support of this key function, with the goal of saving lives. In order to best achieve this goal, hospitals must rapidly organize a command structure and implement the disaster plan for casualty care and resource mobilization. In the United States, the most commonly utilized command structure is the hospital version of ICS, termed HICS, in view of its modular structure around the same five key elements as ICS (see Fig. 8-2) that provides the flexibility to adapt to all forms of emergency events.18

Surge

In most disasters, there is no standard method for notification of a hospital to which casualties are being transported. It is not uncommon for hospital personnel to first become aware of a disaster and imminent casualty arrival from the news media, or even from the arrival of the first casualties without warning. Hospitals should expect no more than 10 minutes of warning before casualties arrive following most urban disasters.17 In this time the most urgent preparation that must be made in order to avoid an uncontrolled inundation is a rapid development of space for the casualties (surge capacity), and a rapid mobilization of resources such as stretchers, medical supplies and equipment, and medical and nursing personnel to care for the casualties (surge capability). The priority for this surge must be in the three most needed and utilized hospital units in mass casualty events, the emergency department (ED), where all casualties are initially evaluated, the OR, and the ICU.39 Other spaces should also be cleared for less urgent casualties. Surge capacity requires the discharge or movement of existing patients in these areas to the greatest extent possible, using the process of reverse triage to determine priorities.40,41 Without established and rehearsed hospital disaster plans in place, this immediate mobilization of resources would not be possible, and chaos would soon overwhelm the facility with the incoming casualties.

Perhaps the most appropriate functional definition of surge capacity has been provided in the previously discussed computer modeling study by Hirshberg et al.,24 as the arrival rate of critically injured casualties per hour permitting optimal care to still be provided to individual casualties. Once this is exceeded, degradation in individual quality of care must occur, at which point the welfare of the population must prevail over that of the individual as altered standards of care must be applied. As discussed in the section “Triage,” the sigmoid curve that describes this relationship (Fig. 8-6) is moved to the left with increasing overtriage (see Fig. 8-3), while effective planning and efficient casualty evaluation moves it to the right to increase the casualty load that can be optimally treated. The downslope portion of this curve therefore represents a true mass casualty event in which resources are overwhelmed, while the upper flat portion represents a multiple casualty event in which standard medical care is still effective. It should not be surprising that the relationship of triage accuracy to trauma team workload is also described by a sigmoid curve (see Fig. 8-4), as this workload is an appropriate surrogate for quality of care. The relationship of overtriage to critical mortality discussed in the section “Triage” (see Fig. 8-5) indicates that the result of this degradation of care with increasing casualty loads is death. Together these studies emphasize the essential dependence of casualty outcomes on triage accuracy and efficient casualty throughput.

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FIGURE 8-6 Computer model of mass casualty hospital influx using data from 22 urban terrorist bombings to demonstrate diminishing quality of care with increasing critical casualty load, defining surge capacity as the highest arrival rate (critical casualties/h) at which at least 90% of the optimal level of care can still be delivered to each casualty. (From Hirshberg A, Scott BG, Granchi T, et al. How does casualty load affect trauma care in urban bombing incidents? A quantitative analysis. J Trauma. 2005;58:686–695, Wolters Kluwer Health, Lippincott Williams & Wilkins, with permission.)

Resource Utilization

Disaster plans must be formulated around realistic expectations of casualty flow patterns and hospital resource utilization following disasters, which are derived from published experiences. Only a minority of 10–15% of casualties will be critically injured (see Fig. 8-1 and Table 8-4), and the less seriously injured tend to be the first to arrive. Triage accuracy is essential to avoid overtriaging these casualties into the hospital and wasting the limited resources where they are not needed, leaving the second critical casualty wave with nothing.5 Within the first hour, 50–65% of all casualties to be admitted will arrive at the hospital, during which time a strong command authority and organized system of care is most important. In urban bombing disasters, which could be considered a universal model for all disasters, OR utilization peaks within 1.5 hours but may continue for 48 hours or longer. Anesthesiologists and general, thoracic, and vascular surgeons are in immediate demand, while orthopedic and plastic surgeons are required later. Of all casualties requiring surgery, 36% went directly to the OR from the ED. Approximately one third of all hospitalized casualties were admitted to the ICU, 31% directly from the ED, and as many as 73% required mechanical ventilation.34,39

Principles of Casualty Care

Mass casualty needs are best accommodated by an efficient and organized system of care. ED personnel should be organized into small teams around each stretcher to provide rapid assessment, triage decisions, necessary urgent interventions, and adequate documentation, followed by rapid movement of the casualty onward to successive echelons of care to make way for the next wave of incoming victims.6,12,14,19 Imaging and laboratory tests must be minimized if used at all during this phase of acute casualty influx, to facilitate rapid forward flow of casualties with no backward movements that would create traffic gridlock and chaos.5,6,17 Records must be brief and should be kept with the casualties as they move onward, where they are progressively added so as to provide each new echelon of care sufficient information to allow the appropriate interventions and treatment to proceed. ED, OR, and ICU supervisors, or controllers, should be designated, who are not directly involved in care, to oversee the proper and expeditious movement of casualties to assure an organized response and prevent bottlenecks and confusion.5,6,17,34,42,43 Designated case managers who are assigned to individual casualties as their advocate, to assure continuity of care and proper treatment, have been shown to improve mass casualty care and throughput in this potentially chaotic process.44

Blood utilization tends to be greatly overestimated in disaster casualties, resulting in large amounts of waste of this critical resource as misguided calls go out for donations.14 In fact, it has been shown that only about 1 U of blood is necessary on average for each casualty of smaller disasters, and about 2 U for larger events, which fall well within the normal surge capability of blood banks.45 In both combat and civilian mass casualty events, most blood products that are used tend to be given to a small number of victims.45,46

External and internal security of the hospital facility is an essential component of the disaster medical response and optimal casualty care.14 The priority of a hospital disaster response must be the safety of its staff and physical structure before all else. The hospital should undergo a lockdown as soon as possible to restrict entry to all except staff and those casualties allowed by the triage officer, to prevent its inundation by the media, worried well, families of victims, minimally injured casualties, and volunteers, all of whom consistently flock to the hospital due to its perception as a safe haven for all. A lockdown contributes to reducing overtriage into the facility. Another component of lockdown is to establish a perimeter around the facility to keep people and vehicles away from the actual entrance as an added measure of safety.15 Internal security is also necessary to prevent the critical patient care areas from being overwhelmed and rendered ineffective by the inevitable influx of well-meaning but misguided medical providers who have no role in these areas. Hospital personnel must also be prevented from leaving to run to the scene to “help,” where they have no role and no training, and will become an added burden and possibly secondary victims.17

There should be provision for ongoing care of those routine emergencies that will continue to arrive at any hospital even during a mass casualty event, such as acute chest or abdominal pain, urgent labor in pregnant women, and motor vehicle crashes. The best system for managing these patients is to consider them as casualties and have them get in line and undergo triage and treatment according to the same priorities as the disaster casualties. Without this provision, routine emergency patients will tend to be ignored.

Once the acute casualty influx subsides, all triage and care dispositions can be reassessed in the light of what resources remain. The quality of care can return to normal medical standards. Expectant casualties may now be rendered care if still alive, and all injuries can undergo definitive treatment. Secondary casualty distribution to other hospitals with greater capacity may now occur to expedite definitive and long-term treatment measures.5,6

PATHOPHYSIOLOGY AND PATTERNS OF INJURY FOLLOWING DISASTERS

There are distinct patterns of injury that result from mass casualty disasters, in terms of mechanism and severity. Approximately 80% of all disasters have resulted in bodily injury, emphasizing the importance of surgical leadership in disaster planning and management.5,6,36,43 Furthermore, trauma centers and trauma systems should be the foundation of all local, regional, state, and national disaster response systems, as they have the personnel, equipment, liaisons, and daily experience with managing large numbers of injured patients and rapid decision making that are so necessary in disasters.6,27,37 However, the trauma community has only rarely been confronted with those mechanisms and agents that commonly result in mass casualty disasters, and have little education and training in their detection and management.47 The following section reviews the mass casualty mechanisms most likely to confront health care providers.

Image Explosive Mass Casualty Events

Explosions, whether accidental or deliberate, have a demonstrated capacity for severe injury of large populations. In addition to the devastation of accidental blasts, they are currently the most common weapons of war and terrorism in view of how easily and inexpensively they can inflict immense destruction (Table 8-5).48,49 Of the 93 major terrorist attacks that occurred globally between 1991 and 2000, 88% involved explosions.50

TABLE 8-5 Major Global Terrorist and Accidental Explosive Events

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Blast Physics

A high-energy explosion results from the virtually instantaneous conversion of solids or liquids into gas in the process of detonation. This releases a large amount of energy in a condensed volume, which creates a high pressure in the surrounding medium that propagates radially at hypersonic speeds of 3,000–8,000 m/s as a blast wave. An intense fireball typically surrounds the immediate blast source, representing the strongest energy field, before degrading into the blast wave, and finally into the lower amplitude of sound waves that provides the sound of the explosion. The energy of the blast wave dissipates rapidly in air according to the cube of the distance from the source. In the greater density of water, blast waves propagate three times more powerfully and farther. However, in confined spaces the blast wave magnifies, rather than dissipates, due to its reflection off floors, walls, and ceilings, resulting in a greater magnitude of destruction and injury.51 Terrorist bombings in crowded buses have resulted in mortality rates of 48%, while in open air they have a mortality of only 3–8%.52 An explosion inside a building may collapse the structure, further magnifying injury and death beyond the confined-space effects of the blast alone (see Table 8-5). The Murrah Federal Building in Oklahoma City was partially collapsed by its bombing in 1995. All 163 immediate deaths among 759 total casualties (21.5%) were occupants of this building. Furthermore, among the 361 building occupants, 94% of immediate deaths were in the collapsed portion of the building.53

Blast Pathophysiology

These characteristics of high-energy blast waves cause significant destructive forces on exposed living organisms. Air-containing organs are most susceptible to injury due to the pressure differentials and inertial mismatches at air:liquid interfaces, where turbulence known as spalling shears tissues. A number of studies have shown blast injury to be more severe than routine trauma, with higher ISS, more complex and extensive injuries that require more surgical procedures, longer ICU and hospital stays, and higher mortality. Children tend to be more susceptible to these injuries than adults.22,5456 There are 4 categories of blast injury:

Primary blast injury (PBI) results from the effects of the blast wave traversing the body, and is characterized by the absence of external signs of injury. The air-containing organs—lungs, GI tract, and ears—are most commonly injured, and may take hours to days to manifest this injury.57 Tympanic membrane rupture is a sensitive marker of exposure to the blast wave, but does not correlate well with the severity of injury.58,59 Over 99% of PBI victims are immediately killed, and the small minority of survivors have a relatively high risk (10–20%) of mortality. Immediate deaths are usually due to fatal air emboli from disruption of the alveolar:vascular barrier characteristic of blast lung injury (BLI). Late deaths among survivors are due to intractable respiratory failure. Another marker of severity among victims of PBI is traumatic amputation, which is also characterized by most victims being immediately killed and a high mortality among survivors.6,19,48

Secondary blast injury refers to the impact of objects and debris secondarily stirred up by the blast wave on the body.

Tertiary blast injury results from the body itself being thrown into objects by the force of the blast wave, and is more commonly seen in children due to their lighter weight. Glass shards from shattered windows are a common form of secondary blast injury.60 These are the most common injuries in survivors of blasts, and they are typically noncritical skeletal and soft tissue trauma, though more complex and severe than gunshot wounds and routine trauma as a result of the large magnitude of energy involved.61 A more destructive pattern of terror-related secondary blast injury has been seen in recent years with the inclusion of metal fragments in bombs.54,62

Quaternary blast injury includes miscellaneous forms of tissue damage only indirectly related to the blast. This includes severe burns from exposure to the fireball in the immediate vicinity of the blast source, which also serves as a marker of proximity to the blast and the potential for PBI and multisystem critical injuries that kill most victims immediately, and is associated with a high mortality among the minority of afflicted survivors. Among the survivors of the 1983 suicide bombing of the U.S. Marine barracks in Beirut, 57% of late deaths were from burns.63 Following the Madrid train bombings in 2005, 17.4% of hospitalized survivors suffered thermal burns, of which 64% were second and third degree.59 Other forms of quaternary blast injury are complex extremity and crush injuries from structural collapse, and inhalation injuries from toxic dust and chemicals. Among survivors of the 1993 terrorist bombing of the World Trade Center in New York City, 93% were afflicted with such inhalation injures. The dissemination of biological, chemical, or radiological agents through dirty bombs is included in this category. Both casualties and responders are susceptible to psychological sequelae of major blast events. Early and aggressive mental health interventions for acute stress reactions may prevent the development of long-term problems with post-traumatic stress disorder (PTSD).64 The organic effects of blast injury on the brain may mimic the manifestations of PTSD.59,65

Implications for Mass Casualty Management

An understanding of the pathophysiology of blast injury allows effective planning for its distinct injury patterns. Recognition of the markers of severity, including BLI, thermal burns, penetrating torso injuries, and traumatic amputation, should facilitate accurate triage decisions, and promote effective utilization of hospital resources in the mass casualty setting typically created by major explosions. The prognostic factors that affect the severity and outcome of casualties afflicted by blast injury are essential for meaningful disaster planning and casualty triage and care (Table 8-6).

TABLE 8-6 Prognostic Factors for Explosive Disasters

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Image Biological Mass Casualty Events

Bioterrorism is defined as the intentional infliction of disease and death on large populations through the use of microorganisms or their toxins. In the fall of 2001, separate anthrax attacks on the news media, political figures, and government institutions using letters contaminated with anthrax spores resulted in 5 deaths, 30 documented exposures, and 13,000 people placed on prophylactic antibiotics. A mass casualty event due to a biological pathogen or toxin is therefore a significant risk. This could occur as a result of a viral pandemic or weaponization of bacteria, viruses, or certain toxins produced by microorganisms. Although the skin, mucous membranes, and gastrointestinal tract are potential portals of entry, the respiratory tract is the most efficient avenue for disease transmission. Exposure of the respiratory tract to certain aerosolized biological products (e.g., anthrax, plague, Q fever, and staphylococcal enterotoxin B) causes primarily a pulmonary syndrome. Aerosolization of botulinum toxin and most viruses, on the other hand, produces systemic disease. The number of possible victims is dependent on the type of agent, its virulence, the susceptibility of the population to infectious or toxic effects, and the degree of exposure of the population.66

The US Centers for Disease Control and Prevention (CDC) has defined three categories of biological weapons, classified according to their likelihood and success of use in a terrorist attack.67 Category A weapons have a high potential for large-scale dissemination, adverse effects on public health, and a high mortality rate. In decreasing order of concern, these include anthrax, smallpox, plague, botulinum toxin, tularemia, and viral hemorrhagic fevers. Category B weapons are moderately easy to disseminate, cause significant morbidity and mortality, and require special diagnostic tests. Category C weapons are emerging pathogens that could be weaponized in the future, and include Nipah virus, hantavirus, tick-borne encephalitis (TBE) viruses, yellow fever virus, and multidrug-resistant Mycobacterium tuberculosis. Frontline medical providers who will most likely be confronted with these casualties must know the clinical manifestations of these agents and maintain a high index of suspicion for their occurrence in order to contain any outbreak most rapidly.68

Delayed recognition of a biological event causing mass casualties is a major problem that most distinguishes it from other forms of disaster. In contrast to other conventional and non-conventional weapons, there is usually no obvious scene of attack, and the slower time course of the evolution of the outbreak leads to a slower disaster response that may play out over days to weeks rather than minutes to hours. Victims are often unaware of their exposure and symptoms may take hours or days to develop because of the incubation period required for disease to manifest after the initial exposure. In the interim, the disease may unknowingly be spread to multiple contacts. The patient may first seek help at a doctor’s office, a freestanding medical clinic, or an emergency room risking further spread of the disease to the medical and nursing staff.

The principles of management of a naturally occurring epidemic and an attack with a biological weapon are similar and include: (1) rapid detection and strict isolation of patients, (2) identification and treatment of contacts, (3) strict hospital infection control possibly including hospital lockdown, (4) avoidance of funeral practices allowing close contact with bodies, and (5) vaccination of the at-risk population. An effective system of syndromic surveillance is necessary to rapidly detect patterns of illness over a wide area in order to identify and contain the disease outbreak most expeditiously. These essential community-based public health measures take time and are difficult to achieve. In the meantime, hospitals have to deal with large numbers of patients requiring care. Most or all of these patients will become infected via the inhalation route.69

Routine reverse isolation is sufficient for most diseases except the highly contagious viral hemorrhagic fevers that require strict isolation. Staff must use a Level A protective ensemble in this situation including a self-contained breathing apparatus.

ICU beds, critical care medical and nursing staff, and ventilators will be the critical resources limiting hospital response to seriously ill patients with respiratory failure following mass casualty events of all kinds.34,39 The CDC maintains a supply of 6,000 ventilators in the Strategic National Stockpile, which has recently been augmented by an additional 3,900 LTV 1200 ventilators in October 2009 as recommended by the American Association of Respiratory Care. However, effective use of these unfamiliar ventilators, and the time required to disseminate them for clinical use by ICU staff in afflicted hospitals, represents major challenges. Lack of experience with a biological mass casualty event in the modern era, lack of functional personal protective equipment permitting effective intensive care, and lack of experience with rapid deployment of stockpiled ventilators are limiting factors to an effective medical response to a biological mass casualty event.68

Image Chemical Mass Casualty Events

Toxic chemicals have a well-demonstrated potential to cause severe morbidity and mortality among large populations from either unintentional or intentional release. The worst chemical disaster in history was caused by the accidental release of 40 tonnes of gaseous methyl isocyanate from the Union Carbide plant in Bhopal, India, in 1984, resulting in 6,000 deaths and 400,000 injuries.70 Poison gases caused over 1 million casualties in World War I. The bomb that exploded in the World Trade Center in New York City in 1993 contained enough cyanide to contaminate the entire building, but was destroyed by the blast.71Sarin nerve agent attacks by the Aum Shinrikyo Japanese cult in Matsumoto, Japan, in 1994 (7 deaths and 240 hospital visits) and the Tokyo subway in 1995 (12 deaths and 5,000 hospital visits) resulted in a relatively small number of deaths and a large number of unexposed but worried citizens flooding the health care system. There was also an attempted cyanide release in the latter attack that was unsuccessful.72

There are five types of chemical weapons that could be used in a terrorist attack or otherwise give rise to a mass casualty disaster: nerve agents, blood agents (cyanide), vesicants (blistering), incapacitating agents, and pulmonary agents. Nerve agents and cyanide are the most likely chemicals to be used. Medical providers must have a working knowledge of the clinical manifestations and treatment of these agents if mass casualties are to be most effectively managed (Table 8-7).

TABLE 8-7 Potential Chemical Terrorism Agents

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Nerve agents are organophosphate compounds that inhibit the action of cholinesterase at the postsynaptic and neuromuscular junctions resulting in excess acetylcholine causing a cholinergic crisis.73 Most insecticides are in this category. The symptoms and signs of a cholinergic crisis are due to the muscarinic (postsynaptic nerve cell membrane, smooth muscle cell, and secretory glands) and nicotinic (skeletal muscle and postsynaptic ganglia) effects of acetylcholine. The muscarinic effects involve hypersecretion and an overall wet patient, and may be classified according to the DUMBBELS mnemonic (diarrhea, urination, miosis, bronchorrhea, bronchospasm, emesis, lacrimation, salivation). The pulmonary effects result in a low pulmonary compliance. The nicotinic effects include fasciculations, flaccid paralysis, tachycardia, and hypertension. The heart rate may vary during a cholinergic crisis due to the opposing actions of the nicotinic and muscarinic effects. These patients tend to die of respiratory failure.

The overwhelming majority of casualties who arrive at the hospital will have either mild or no exposure to the nerve agent. Patients who are comatose, seizing, or apneic are classified as severely injured. Supine patients who are wheezing, fasciculating, or incontinent are classified as moderately injured. Ambulatory patients are classified as mildly injured.

Five nerve agents have been produced as weapons in increasing order of toxicity (see Table 8-7). The G and V designations are from NATO nomenclature. G agents are water soluble and tend to wash off more easily, and are therefore less toxic than the more oily and persistent V agents. VX is so toxic that a fraction of one droplet on the skin could kill an adult human. There are two separate antidotes for a cholinergic crisis caused by these chemicals. Atropine blocks the muscarinic effects of acetylcholine by competitive inhibition of acetylcholine at the postsynaptic cholinergic receptors. Atropine, however, does not block the nicotinic effects because it has no effect on the neuromuscular (striated muscle) end plate. The antidote for the nicotinic effects is pralidoxime chloride (2-PAM), a drug that functions like a “molecular crowbar” separating the organophosphate nerve agent from cholinesterase thereby enabling metabolism of the acetylcholine. Unfortunately irreversible binding between the organophosphate and cholinesterase occurs with time, a phenomenon known as aging. The aging time varies from 2 minutes for soman to several hours for sarin. 2-PAM must be given prior to the onset of aging in order to be effective. Its efficacy will obviously depend on how quickly after initial exposure it is administered.72

The recommended initial antidote is atropine 2 mg IM and 2-PAM 600 mg IM for mild to moderate nerve injury and atropine 6 mg IM and 2-PAM 1,200 mg IM for severe injury. Subsequent doses of atropine in hospital should be titrated to control the muscarinic symptoms.72

Blood agents are basically forms of cyanide, which is a highly effective chemical weapon when used in a closed space such as the “gas chambers” of the Nazi concentration camps. It is a highly volatile gas and disperses rapidly, making it unsuitable as a military or terrorist weapon in an open area.

The cyanide ion has a high affinity for the ferrous ion in the mitochondrial cytochrome system. Oxidative phosphorylation is interrupted when cyanide binds to cytochrome A3 rapidly leading to anaerobic metabolism and lactic acidosis. The cyanide ion is generated by two chemicals: hydrogen cyanide and cyanogen chloride. The portals of entry for both are the respiratory tract, the GI tract, and the skin.74

The signs of moderate or severe exposure are a bright red appearance of the skin and venous blood, metabolic acidosis, and the odor of “bitter almonds,” although these tend to be very late and premorbid signs not likely to respond to treatment. Severe exposure causes coma, apnea, and cardiac arrest. Patients exposed to cyanide should be brought into open air and well-ventilated spaces as soon as possible. They are treated by inhalation of a 0.3-mL ampule of amyl nitrite or 10 mL of 3% sodium nitrite (300 mg) IV over 3 minutes. The goal is to produce methemoglobin that binds to the cyanide ion creating cyanomethemoglobin. Following nitrite administration, 50 cm3 of a 25% solution of sodium thiosulfate (12.5 g) should be administered IV to convert cyanomethemoglobin to the inactive thiocyanate ion that is excreted in the urine. Protective clothing and masks should be used by the treatment teams, and treatment should be carried out in open and well-ventilated spaces.

Vesicants are liquid chemical weapons that cause burns to the skin and mucous membranes after initial exposure and long-term bone marrow suppression. The principles of management include decontamination to remove the agent and minimize time of exposure, and treatment of the burn wound and hematologic abnormalities. Large-scale use of vesicants during World War I and the Iran–Iraq War in the 1980s resulted in tens of thousands of casualties. However, it is unlikely that vesicants will be used in a terrorist attack because of the difficulty in deploying the weapon on a large scale.

Chlorine and phosgene are pulmonary agents that cause pulmonary edema and respiratory insufficiency. Exposure to these chemicals causes chest tightness progressing to cough, hoarseness, stridor, and hypoxia over a period of 2–4 hours. The pulmonary injury is similar to the effects of inhalation of smoke from burning plastic. Chlorine binds with the water of the respiratory tract’s mucous membranes to form hydrochloric acid, creating severe injury. It tends to only involve the upper respiratory tract as it is so noxious that it will be expelled before reaching the lower tract. Phosgene tends to injure the pulmonary parenchyma of the lower tract. Terrorist deployment of pulmonary agents would be difficult because a large volume of gas is required to cause a mass casualty event unless the gas is released in a closed space.

A chemical mass casualty event requires specific alterations to the hospital response. If a nerve agent or pulmonary agent is used in the attack (the most likely scenarios), the result will most likely be a “mass hysteria” rather than “mass casualties.” Most of the severe cases will die in the field in view of how rapidly the symptoms progress to respiratory failure, making more of a mass mortality rather than mass casualty event. Therefore, the preparation for treatment of mass casualties from these agents is largely futile, as the treatment regimens described above for single patients will not be amenable to dozens, hundreds, or thousands of casualties within the short time period required to treat those most at risk of death. Treatment facilities would also be unlikely to have enough ventilators or ICU capacity and capability immediately available to manage mass casualties. A large number of worried well and mildly exposed patients will flood the hospital as happened after the Aum Shinrikyo sarin attacks in Japan. Hospital security and hospital lockdown are critical elements in response to a chemical event to prevent contamination of the facility and the hospital staff, as happened in Tokyo where many casualties were hospital personnel.72 Decontamination showers complete the process.

Decontamination outside of the hospital is important. Early decontamination protects the patient from further exposure. Late decontamination protects the medical staff. Simple removal of clothing, or gross decontamination, eliminates 80% or more of most contaminants and can be done quickly to allow treatment and hospital admission of the most seriously injured. More thorough technical decontaminationinvolves a thorough washing with soap and water and shaving of hair. All clothing and effluent from this process must be carefully collected for proper disposal to prevent further spread. Patients in a cholinergic crisis require resuscitation by health care personnel wearing personal protective equipment in the decontamination zone. Well-ventilated spaces are important for this process to prevent off-gassingof fumes from the casualties that may afflict providers.

Efficient resuscitation of large numbers of casualties in cholinergic crisis or with cyanide or pulmonary agent poisoning by unpracticed staff wearing bulky protective clothing is unrealistic. The decontamination process cannot involve treatment to any clinically relevant extent. Surgeons and anesthesiologists should be aware of the potentiating effects of nerve agents on neuromuscular blockade in the event that surgery is required to treat a trauma patient exposed to nerve agents.

Image Radiological Mass Casualty Events

The dispersal of radioactive agents to inflict injury and death on large populations is theoretically possible, and has occurred in a limited number of documented instances. However, the fears of mass casualty events from radiological agents are far out of proportion to actual risks, making this more of a weapon of mass hysteria than mass destruction. There are three types of radiological mass casualty events: a “dirty” bomb, an attack or accident at a nuclear facility (including nuclear-powered ships and submarines), and the detonation of a nuclear bomb in an urban area. The clinical and social consequences of these three scenarios differ significantly.75

A “dirty” bomb is a conventional explosive device mixed with radioactive powder or pellets. The explosion results in dispersion of a radioactive plume to the surrounding area. The blast effect depends on the size of the bomb. The radioactive contamination is usually clinically insignificant and limited to the immediate area surrounding the blast. Although a “dirty” bomb is not a “nuclear” device, the “radioactivity” associated with the explosion is likely to create panic sending a large number of uncontaminated worried well patients to the hospital. Most of the injuries will be due to the blast effects of the explosion. A small fraction of the patients will require radioactive decontamination.75,76

The accident at the Chernobyl nuclear reactor in the Ukraine on April 26, 1986, was caused by a chain of human errors and technical malfunctions causing a series of explosions ultimately expelling 25% of the reactor core. Two people died from blast injury, 1 from a myocardial infarction, and 28 from massive radiation exposure. Two hundred and thirty-eight survivors had acute radiation syndrome (ARS). Many of these patients had cutaneous burns. Thousands of people in Northern Europe were exposed to the radioactive fallout with long-term adverse health consequences.76

The casualty profile of a nuclear reactor incident includes some patients with blast injury, a group of patients with lethal radiation exposure, and a larger group of survivors with burns and ARS. The magnitude of such an incident depends on whether or not the integrity of the reactor is breached.

The explosion of a nuclear bomb results in massive release of energy in the form of heat, light, air pressure, and radiation after either fission (splitting of uranium-235 or plutonium) or fusion of the hydrogen isotopes deuterium and tritium. A large fireball occurs at the center of the explosion vaporizing everything including soil and water. The radioactive material is thrust high into the atmosphere creating the “mushroom” cloud. This material, carried by the prevailing winds, solidifies and eventually falls to the ground creating radioactive fallout.

Two types of nuclear devices are of concern: a tactical nuclear weapon in the form of an artillery shell (“suitcase bomb”) and a strategic nuclear bomb. A tactical nuclear device can be delivered and detonated by a single person causing an explosion ranging in power from 72 tonnes to 15 kilotonnes of TNT. The power of strategic nuclear weapons ranges from hundreds of kilotonnes to megatonnes of TNT.

Following explosion of a nuclear device, there will be a zone of destruction extending several kilometers from ground zero depending on the size of the device. There will be very few, if any, survivors in the zone of destruction. The electromagnetic pulse accompanying the explosion will likely destroy all electronic equipment inactivating cars, cell phones, computers, and other devices.

The treatment of blast and burn injuries following a nuclear explosion is based on the accepted principles of trauma care. Radiation injury is uniquely associated with a nuclear incident, and is caused by any form of ionizing radiation. This damages living tissue through its immediate direct energy, as well as indirectly from the long-term creation of toxic hyperoxide molecules. The rapidly dividing tissues of the gastrointestinal tract and bone marrow are most susceptible to injury. The factors that determine the severity of the biological effects are time of exposure, distance from the source, and degree of shielding.75,76

It is important to distinguish radiation exposure from radiation contamination, as only the latter poses any level of risk to health care workers, and usually that risk is minimal. Radiation exposure does not make a person “radioactive.” ARS is a series of incremental symptoms after exposure to at least 0.7 Gy (1 Gy = 100 rad of absorbed radiation). It is characterized by an initial prodromal phase of rapid onset of nausea, vomiting, and malaise. This is followed by a latent phase. After approximately 1 week GI symptoms develop. Bone marrow depression can develop within 6 weeks after radiation exposure.7578

Exposure to 6–8 Gy results in bloody diarrhea after a latency period of several days. All of these patients develop bone marrow depression. Initial treatment includes fluid and electrolyte replacement. Although there are a number of isotope-specific treatments that have been used, including potassium iodide, chelating agents, binders, and purgatives, none of these have any substantial benefit. Even bone marrow transplant has shown disappointing results in casualty outcomes. A dose of 10 Gy is the maximum survivable absorbed dose of radiation. Exposure to 20–40 Gy of radiation results in hypotension, coma, and seizures. Death typically occurs within 3 days of exposure even with maximal medical therapy. This dose of radiation is so great that victims would be unlikely to survive the blast effect. However, any victims with the neurovascular syndrome who do survive should receive comfort care only.77,78

Time to first emesis and time to first lymphocyte depression are very reliable triage tools as they directly correlate with the absorbed radiation dose. Emesis or diarrhea within 1 hour indicates an expectant patient who will die even with maximal medical treatment and should be given comfort care only. Onset of these symptoms within 2–4 hours indicates potential salvageability and should have immediate treatment, while longer onset should indicate minimal treatment. Clinically apparent bone marrow depression begins 10 days to 6–8 weeks following exposure. A 50% drop in the lymphocyte within 24 hours indicates significant radiation exposure and an expectant triage assignment. Treatment options include hematopoietic growth factors, prophylactic antibiotics, and bone marrow transplantation. Early severe bone marrow depression is a bad prognostic sign and has important implications for triage in a mass casualty situation.75,76

Casualties must undergo initial decontamination outside of the ER. Gross decontamination with removal of clothing and a soap and water shower eliminates more than 90% of the radioactive contamination. The clothing should be placed in plastic bags. This allows initial triage and evaluation to proceed with minimal risk to the health care team. Technical decontamination should then be done for stable patients. This procedure involves a thorough scrubbing of the body with bleach products, shaving or washing all hair, and covering all open wounds after cleansing to prevent them from becoming portals of entry for radioactive material. The results of technical decontamination should be monitored with dose-meter devices. All water, clothing, and other products of decontamination should be collected and stored in plastic bags to prevent contamination of the environment. The US Department of Energy maintains a 24-hour hotline for questions about radiation exposure at the Radiation Emergency Assistance Center/Training Site (REAC/TS) in Oak Ridge, Tennessee (865-576-1005).77

Unstable patients should not have necessary hospital admission or immediate lifesaving treatment delayed for radiological decontamination as there is no danger to the hospital or health care providers as long as standard universal precautions are practiced. Medical care trumps decontamination in this setting.77

SUMMARY

Disasters and mass casualty events pose unique challenges in surgical management. Surgeons will be among the most prominent first receivers of casualties from most disasters. They should be leaders in the disaster planning process, and must understand the altered approaches to medical care, and the importance of being a part of a larger team framework, which are necessary to optimize casualty outcomes in these settings.43 Trauma centers and trauma systems have the necessary infrastructure, in terms of supplies, equipment, personnel, liaisons, and experience for disaster management, and should serve as the foundation for local, regional, and national disaster systems.27,36,37

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