Chapter 8: Disaster and Mass Casualty

No one can predict the time, location, or complexity of the next disaster. The management of the medical effects of contemporary disasters, whether natural or man-made, is one of the most significant challenges facing medical providers today. Disaster medical care, including trauma care, is not the same as conventional medical care. Disaster medical care requires a fundamental change (“crisis management care”) in the care of disaster victims in order to achieve the objective of providing the “greatest good for the greatest number of individuals.”^1,2,3,4,5 The demands of disaster medical care have changed over the past decade, both in the scope of medical care, the type of threats, and the field of operations (Fig. 8-1). Mass casualty incidents (MCI) are events causing numbers of casualties large enough to disrupt the health care services of the affected region. This is in contrast to multiple casualty events in which medical resources are strained (prehospital and/or hospital resources) but not overwhelmed. Demand for resources always exceeds the Supply of available resources in a disaster.

Natural disasters may be classified as sudden-impact (acute) disasters or chronic-onset (slow) disasters.⁶ Sudden-impact natural disasters generally cause significant mortality and morbidity immediately as a direct result of the primary event (eg, traumatic injuries, crush injuries, drowning).⁷ Chronic-onset disasters cause mortality and morbidity through prolonged secondary effects (eg, infectious disease outbreaks, dehydration, and malnutrition). Earthquakes, tsunamis, landslides, and wildfires are examples of sudden-impact disasters. Chronic-onset disasters include famines, droughts, and infectious disease epidemics.

Man-made disasters may be unintentional or intentional (terrorism).^1,8,9,10 The spectrum of agents used by terrorists is limitless and includes conventional weapons, explosives, and weapons of mass destruction (biological, chemical, and radioactive agents). Over 70% of terrorist attacks involve the use of explosive weapons. Improvised explosive devices (IEDs) are a particular concern for trauma providers (Fig. 8-2). Such incidents present a significant challenge due to the complexity of injuries (primary, secondary, tertiary, and quaternary blast injuries).^{1,7,8,9,10,11} Responders must also be aware of the potential for secondary strikes directed at harming medical personnel. Terrorists do not have to kill people to achieve their goals. They just have to create a climate of fear and panic to overwhelm the health care system (examples: sarin/anthrax attacks).

Principle 1

Medical providers cannot utilize traditional command and control structures when participating in disaster response. The Incident Command/Management System is the accepted standard for all disaster response. Functional requirements, not titles, determine the organizational structure of the Incident Command/Management System.

Principle 2

All disasters are not different. Disaster response includes basic concerns (similar to the ABCs of trauma care) that are the same in all disasters (Table 8-1). A single emergency operations plan for many different situations is more effective than multiple separate disaster plans (all hazards approach).^1,2,3,4,11 The difference in disasters is the degree of disruption of the medical and public health infrastructures and the amount of outside assistance (regional, national, international) that is needed to meet the needs of disaster victims. Rapid assessment by experienced disaster responders will determine which “functional capacities” are needed to meet the demands of the acute phase of the disasters.

Principle 3

Effective “surge capacity” is not based on well-intentioned and readily available volunteers. Disaster responders must understand the basic principles of disaster response (ICS, disaster triage, gross decontamination) to be effective members of the disaster teams.

Principle 4

Trauma care in disasters is not the same as conventional trauma care. Disaster care of traumatic injuries requires a fundamental change in the approach to the care of victims (“crisis management care”). The objective of conventional trauma care is the greatest good for the individual patient. Severity of injury/disease is the major determinant of medical care. The objective of disaster trauma care is the greatest good for the greatest number of victims. Determinants of care are severity of injuries, likelihood of survival and available resources (personnel, logistics, evacuation assets).^1,4,7,9

Medical providers cannot utilize traditional command structures when participating in disaster response. The Incident Command System (ICS) is a modular/adaptable system for all incidents and facilities and is the accepted standard for all disaster response. The Hospital Incident Command System (HICS) is an adaptation of the ICS for hospital use, allowing effective coordination in disaster preparedness and response activities with prehospital, public safety, and other response organizations. The trauma system is an important component of the ICS.

Functional requirements, not titles, determine the ICS hierarchy (Fig. 8-3). The organizational structure of the ICS is built around five major management activities—incident command, operations, planning, logistics, and finance/administration.^1,10,11 Key activities of the five categories are listed in Table 8-2.

The structure of the ICS is the same regardless of the nature of the disaster.^1,10,11,12 The difference is in the particular expertise of key personnel. An important part of disaster planning is the identification of the incident commander and other key positions before a disaster occurs (24 h/d–7 d/wk). Each person within the command structure should supervise only 3–7 persons. This is quite different from conventional prehospital/hospital command structures. All medical providers must adhere to the structure of the ICS in order to integrate successfully into the disaster response team and avoid many negative consequences including

• Death of medical personnel due to lack of safety and training

• Lack of adequate medical supplies to provide care

• Staff working beyond their training or certification

• Lack of coordination

Search and Rescue

Many countries, including the United States, have developed specialized search and rescue teams as an integral part of their national disaster plans (Fig. 8-4).^1,13,14

Members of these teams, who receive specialized training in confined space environments, include the following:

• A cadre of trauma specialists

• Technical specialists knowledgeable in hazardous materials, structural engineering, heavy equipment operation, and technical search and rescue methodology

• Trained canines and their handlers

Triage

Triage is a dynamic decision-making process of matching patients’ needs with available resources. Triage is the most important and psychologically challenging aspect of disaster medical response, both in the prehospital and hospital phases of disaster response. Disaster triage is significantly different from conventional trauma triage. The major objective and challenge of disaster triage is to identify the small minority of critically injured patients who require urgent lifesaving treatments, including damage control surgery, from the larger majority of noncritical casualties.

Critical patients having the greatest chance of survival with the least expenditure of time and resources are prioritized to be treated first. Review of the literature from major disasters estimates that 15–25% of victims are critically injured, and the remainder of victims are noncritical casualties.^1,4,7,11

Triage Errors

Triage errors, in the form of undertriage and overtriage, are always present in the chaos of mass casualty events. Undertriage is the assignment of critically injured casualties requiring immediate care to a “delayed” category. Undertriage leads to treatment delays with increased mortality and morbidity. Overtriage is the assignment of noncritical survivors with no life-threatening injuries to immediate urgent care. The higher the incidence of overtriage, the more the medical system is overwhelmed with increased mortality and morbidity. The level of acceptable over/undertriage in a MCI and the best method for evaluation of triage effectiveness in a MCI are controversial.

Levels of Triage

Three levels of disaster medical triage have been defined. The level of disaster triage utilized at any phase of the disaster will depend on the ratio of casualties to capabilities. Many mass casualty incidents will have multiple levels of triage as trauma patients move from the disaster scene to definitive medical care.^{1,2,3,4,12,15,16}

Field triage (level 1) is the rapid categorization of victims potentially needing immediate medical care “where they are lying” or at a casualty collection center. Victims are designated as “acute” or “nonacute.” Color coding may be used.

Medical triage (level 2) is the rapid categorization of victims by experienced medical providers at a casualty collection site or fixed/mobile medical facility.^15,17 Victims are classified into the following categories:

• RED (urgent). Lifesaving interventions (airway, breathing, circulation) are required (Fig. 8-5).

  YELLOW (delayed). Immediate lifesaving interventions not required.

• GREEN (minor). Minimal or no medical care or psychogenic casualties.

• BLACK. Deceased victims.

Expectant Category of Triage Victims

The “expectant” category of victims is unique to mass casualty incidents. Victims are classified as “expectant” if they are not expected to survive due to the severity of injuries (massive crush injuries or burns) or underlying diseases and/or limited resources. The expectant category of triage was first developed given the threat of weapons of mass destruction (biological, chemical, radioactive) during military conflicts but is now utilized in all disasters. Traditionally this category of disaster casualties has been classified as “yellow or delayed” category. Currently many triage systems classify expectant victims as a separate category with a different color designation. Classification of the expectant category of disaster victims remains controversial. Many models have been proposed based on severity of injury, age, underlying diseases, and hemodynamic stability of victims at time of rescue.^1,2,5,7 Criteria that are currently utilized as guidelines for the expectant category are

• Cardiac arrest on scene

• Severity of comorbid diseases

• Requirement for intubation and ventilation on scene

• Head injuries

• Massive burns (>80% total body surface area)

Evacuation triage (level 3) is often a neglected area of disaster preparedness. Priorities for transfer to medical facilities are assigned to disaster victims using the same color classification as medical triage.

Definitive medical care refers to care that will improve, rather than simply stabilize, a casualty’s condition. Maximally acceptable care for all trauma patients is not possible in the early stages of the disaster given the large number of victims in a MCI. In the initial stage of the disaster, only minimally acceptable trauma care to provide lifesaving interventions is possible.^1,14,15,16

Damage control surgery is an important component of crisis management care. Damage control surgery limits trauma interventions to control of hemorrhage and contamination. Damage control surgery was initially developed for abdominal trauma with uncontrolled hemorrhage but has expanded to all other trauma specialties in disasters.^18,19,20 Spinal and regional anesthesia, as well as intravenous sedation and intraosseous infusions, are important adjuvants to trauma care in disasters.

Evacuation may be useful in a disaster to decompress the disaster area and provide specialized trauma care for specific casualties, such as those with burns and crush injuries. Trauma providers with expertise in critical care are increasingly valuable resources in disasters.

Special considerations during evacuation include¹:

• A decrease in cabin pressure occurs as altitude increases. Tapped gas in any body cavity can cause serious complications as it expands on ascent. Special attention must be paid to trapped gas within the thorax, cranium, eye, and the gut in the presence of an ileus. Patient care appliances, such as endotracheal tube cuffs, are also susceptible.

• The partial pressure of oxygen in the ambient air decreases with increasing altitude. Monitoring with pulse oximetry is important.

• Takeoffs and landings present unique challenges, especially with head injury patients.

• Young children, burn patients and postsurgical casualties are particularly susceptible to temperature changes during evacuation.

Disasters involving weapons of mass destruction (WMD), whether accidental or man-made (terrorism), are a significant challenge for medical providers for several reasons^1,10,16:

• WMD have the potential to produce casualties in numbers large enough to overwhelm health care systems, including surgical capacities.

• WMD may produce large numbers of expectant victims.

• WMD may produce a “contaminated” environment. Trauma providers must be able to perform triage, initial stabilization, and possible definitive surgical care outside traditional health care facilities.

• WMD produce significant numbers of “psychogenic” casualties, greatly complicating rescue and triage efforts.

Biological terrorism is the intentional use of microorganisms or toxins to kill or injure humans. Exposure to biological agents may be accidental or intentional (terrorism).^1,10 Agents believed to have the greatest potential as bioterrorism weapons are listed in Table 8-3.

Routes of Exposure

The route of exposure of most concern with biological agents is inhalation of the agent. Oral exposure to biological agents may occur directly or secondarily after an aerosol attack. Agents with the highest potential for person-to-person transmission (pneumonic plague, smallpox, and viral hemorrhagic fevers) constitute the greatest hazard. The most effective and important protection against biological agents is physical protection. Removal of clothing will eliminate greater than 85% of the agents. Any dermal exposure should be treated immediately by gross decontamination with soap and water.

Prophylaxis and Therapy

Medical defenses against some biological agents are limited. Vaccines are available to protect against some biological agents (anthrax, smallpox) and antibiotics may be effective against bacterial agents such as anthrax, plague and tularemia if given early enough. Disasters involving biological agents have a significant impact on the health care system for the following reasons:

• Terror in affected populations and medical care systems

• Overwhelming casualties and significant ICU/special medication needs

• Problems with handling dead victims

Chemical agent release may be unintentional (industrial accidents) or intentional (terrorism).^1,10,16 Many chemical agents, especially warfare agents, are liquids and must be dispersed to be maximally effective. There are three general methods of dispersion:

1. Aerosolizing with an aerial sprayer

2. Aerosolizing the liquid with an explosion (IED + chlorine tanker)

3. Allowing the liquid to evaporate (Tokyo Sarin attacks)

Time is of the essence in the decontamination and treatment of chemical agent casualties. Treatment areas should be upwind and uphill from the contamination site. It is important that decontamination facilities be separate from the emergency department.

Specific Chemical Agents

Nerve Agents

Nerve agents are toxic relatives of organophosphate insecticides. They cause effects by disrupting the normal mechanism by which nerves communicate with muscles, glands, and other nerves (Fig. 8-6). Nerve agents enter the body either percutaneously (through the skin) or by inhalation (through the lungs). Clinical effects of nerve agents are summarized in Table 8-4. The most important nerve agents are GA (Tabun), GB (Sarin), GD (Soman), GF, and VX.

Treatment of Nerve Agents

• Atropine, 2–6 mg IV: Antidote for smooth muscles and exocrine glands^1,10,16

• Pralidoxime (2-PAM): Antidote for skeletal muscle sites:

  • Atropine sparing effect.

  • Timing of 2-PAM administration is critical. Binding of nerve agents to cholinesterase can become irreversible with time.

Valium (Diazepam) is used as an anticonvulsant as needed. The traditional Mark 1 Kit contains two spring-loaded injectors of atropine and 2-PAM. A new product, DuoDote, contains atropine + 2-PAM in a single auto-injector. Antidotes may be given by medical personnel in appropriate protective gear prior to decontamination.

Vesicants

Vesicants are agents that cause erythema and vesicles on the skin as well as injury to the eyes, airways and other organs. Key to treatment of these agents is thorough decontamination as soon as possible. Sulfur mustard has no specific antidote. BAL is the specific antidote for lewisite.^1,10,16

Hydrogen Cyanide

Hydrogen cyanide has a long history as a deadly poison as it causes death within minutes of exposure. Antidote is hydroxocobalamin 5GM IV (preferred) or cyanide antidote kit.

Pulmonary Agents

Pulmonary agents cause pulmonary edema which can be exacerbated by exertion. Phosgene and chlorine are the most common agents. The pulmonary edema caused by phosgene and chlorine causes dry-land drowning to the point that the casualty can become hypoxic and apneic.

Riot Control Agents (tear gases or lacrimators)

Treatment is symptomatic with copious irrigation of eyes and skin with water or normal saline.

Release of radioactive material would most likely involve the following scenarios¹:

• Detonation of a nuclear device

• Meltdown of a nuclear reactor—melting of the nuclear fuel within a reactor with release of radioactive materials into the environment (Fukushima nuclear accident)

• Dispersal of material through use of a conventional explosive (radiological dispersal device (RDD) or “dirty bomb”)

• Nonexplosive dispersal of radioactive material

Radiation types include nonionizing radiation (no tissue damage) and ionizing radiation (tissue damage). Electromagnetic radiation and particle radiation (radiation dust) are the two types of ionizing radiation seen in disasters. Radiation exposure may be external irradiation (whole body or localized) and/or contamination (radiation debris)—internal and external contamination. Responders must assume both external and internal contamination when responding to disasters involving radiation agents.

Medical Effects of Ionizing Radiation

• Focal tissue damage and necrosis

• Acute radiation syndrome (result of whole body exposure)

• Long-term effects (thyroid cancer, leukemia, etc)

Treatment of Radiation Casualties

• Removal of clothing in victims with external contamination eliminates more than 90% of the contamination.

• Radiation effects are delayed—trauma triage is done according to conventional trauma protocols.

• Decontamination—before, during, or after initial stabilization, depending on severity of injury.

• Emergency surgery, as well as closure of surgical wounds, should be performed early.

• Know the limitations of your radiation detection devices. Protect yourself until victim free of all radiation contamination.

Decontamination

The basic principles in response to any hazardous-material incident are the same regardless of agents involved. Removal of clothing and jewelry may reduce contamination by up to 85%. It is important for medical providers to protect themselves during decontamination with the appropriate level of personal protective equipment (PPE).

Blast Injuries

Blast injuries are multisystem, life-threatening injuries that are caused by many types of disasters. Blast injury victims tend to sustain more traumatic injuries, varied anatomic locations of injury and greater injury severity scores (ISS) than other trauma victims. The predominant postblast injuries among survivors involve conventional penetrating and blunt trauma injuries.^1,7,8,10,11

Mechanism of Injury

Explosives may be classified as high-order or high-energy (HE) or low-order or low-energy (LE) explosives and cause different patterns of injury. High-energy explosives (C-4, Semtex, ammonium nitrite-fuel oil, TNT) detonate to produce a defining overpressurization shock wave. Low-energy explosives (pipe bombs, Molotov cocktails) deflagrate to produce a subsonic explosion and lack the overpressurization shock wave. An improvised explosive device (IED) attack is the use of a “homemade bomb and/or destructive device” designed to cause death or injury. The survivability, mortality, and morbidity from a blast injury correlate significantly with whether victims are in open or closed space explosions. Underwater blasts are significantly more devastating as the lethal radius of an underwater explosion is about 3 times that of a similar explosion in air.

Primary Blast Injury

Primary blast injuries (PBIs) result from the direct effect of the blast wave (traveling at supersonic speeds) on the body. Primary blast injuries affect the gas-containing organs: the lung, the ear, and the gastrointestinal tract. The most common lung injury is a pulmonary contusion. Other pulmonary injuries range from pneumothoraces/hemothoraces to A–V fistulas (source of air emboli.) Abdominal blast injuries are a significant cause of mortality and morbidity. Abdominal blast injuries may be occult and difficult to diagnose and range from hemorrhage to mucosal ischemia—bowel necrosis and perforations. The middle ear is particular sensitive to blast injuries and tympanic membrane (eardrum) rupture may be a useful marker for blast injury. However, isolated rupture of tympanic membranes without other symptoms is NOT a marker for high risk of associated blast injuries.

Secondary Blast Injury

Secondary blast injuries are caused by flying debris generated by the explosion (Fig. 8-7). A favorite practice for terrorists is packing IEDs and other explosives with screws, bolts, nuts, and other sharp small objects.^1,11,18 Significant soft tissue, internal and orthopedic trauma are frequent from propelled missiles.

Tertiary Blast Injury

Tertiary blast injuries are caused by propulsion of the body by the shock wave into solid objects (eg, walls). Tertiary blast injury casualties sustain major blunt trauma injuries, such as traumatic brain injuries, solid organ injuries, and complex orthopedic injuries. Penetrating injuries are not uncommon when the victims are impaled on objects in the environment.

Quaternary Blast Injury

Miscellaneous blast injuries encompass all other injuries cause by the blast, including burns, crush injuries, compartment syndromes and toxic inhalations (carbon monoxide, dust, hot gases).

Crush injury is defined as compression of body parts causing localized muscle and nerve damage and is seen in both natural and man-made disasters (Fig. 8-8). The lower extremities are the most common site of crush injuries. Crush syndrome, first recorded in the bombings in London during WWII, is localized crush injury with systemic manifestations. The systemic manifestations are caused by traumatic rhabdomyolysis (muscle breakdown and the release of toxic muscle cell components and electrolytes into the circulatory system). Metabolic abnormalities include acidosis (low blood pH levels), hyperkalemia, and hypocalcemia.

Important guidelines for prehospital management of victims with crush injuries have now been established and implemented with search and rescue teams.^1,5,10,13,17

• Pretreat casualties with prolonged crush (>4 hours) as well as those with abnormal neurologic or vascular exams with 1–2 L of normal saline before releasing crushing object whenever possible.

• If not possible to pretreat, consider applying a tourniquet to crushed limbs and maintain until IV fluid administration is initiated. Risk of acute deterioration and death with sudden release of pressure on the involved extremity (reperfusion syndrome) is a significant risk. Reperfusion syndrome is manifest by acute hypovolemia and metabolic abnormalities.

• Monitor casualties for symptoms of compartment syndrome (fracture not mandatory for compartment syndrome to develop)

• Field amputation of a crushed extremity is considered as last resort and should be as distal as possible.

Clinical competencies, not titles, determine the roles of medical providers in disaster response. Disaster management teams are designed and trained to provide specific “functional” areas of disaster care such critical care, pediatrics, obstetrics, and acute and trauma surgery, especially when the casualty load is unknown. The complexity of today’s disasters demands civilian and military partnerships as key to effective disaster response.

Disaster preparedness must include practical drills to ascertain the true magnitude of system problems, not just tabletop exercises. Mass-casualty drills must include three phases: preparation phase, exercise management phase, and patient treatment phase. The preparation phase must include clear definition of functional areas of responsibility that can be evaluated objectively, not subjectively, during the disaster drill. The exercise management phase includes objective evaluation of all key functional roles in the ICS. The patient treatment phase includes objective valuation of well-defined functional capacities such as triage, initial resuscitation, definitive care, evacuation, and care of dead victims.^1,11,21

The mass casualty incident response is a consistent approach to disasters based on an understanding of the common features and the response expertise they require in all phases of the disaster response. The goal of disaster medical response is to reduce the critical mortality associated with a disaster. Critical mortality rate is defined as the percentage of critically injured survivors who subsequently die.^1,8 Numerous factors influence the critical mortality rate, including:

• Triage accuracy, particularly the incidence of overtriage of victims

• Rapid movement of patients to definitive care

• Implementation of damage control procedures

• Coordinated regional disaster preparedness