CHAPTER 14 PREHOSPITAL CARE OF BIOLOGICAL AGENT–INDUCED INJURIES
On a busy Baghdad bridge spanning the great Tigris River coursing Iraq from north to south, a crowd of people intermingled in their bidirectional flow. Most were hurrying to and from the nearby market on the east side of the river below. Some were carrying parcels, others infant children in their arms or on their backs. Someone shouted something; it was never determined who or what, but those within hearing interpreted the alarm as a warning, presumably of an improvised explosive device (IED) on the bridge. The reaction among the already apprehensive civilians was instant panic and they scattered in all directions. Some attempted to cross to the other side; others tried to retreat from where they were headed, some jumped into the waters below. A herd mentality eliminated all sense of proportion; flight with presumed escape dominated the thought processes of the terrified populace. In the aftermath of the incident, almost 1000 were dead and many more were injured. The causes of death included suffocation, exsanguination from blunt trauma to torso, head injuries, and multiple long-bone fractures. Many drowned. The alleged IED never detonated, nor was it ever identified. The date was August 31, 2005. The inciting event remains a mystery.1 The inciting event, however, exemplifies two phenomena pertinent to the trauma surgeon.
Prehospital care is provided by the most medically sophisticated at the scene and en route to a medical treatment facility (MTF). Such caregivers may be emergency medical technicians (EMTs), paramedics, and even physicians.2 They will be required, by necessity, to perform patient assessment, threat assessment, triage, and first aid until additional help arrives.
Triage is patient-location dependent.3 Casualties from biological agent–induced injuries may be encountered in the field or at the scene of agent exposure. At this level the term “field triage,” as distinguished from “hospital triage,” is appropriate. The word is derived from the French verb “trier,” which means to sort, and dates back to the 15th century and European marketplaces where fur and fiber were sorted according to quality and price. Any number of categories can be designated, but perhaps the simplest is three tiers. Most “patients” are apprehensive, bordering on hysteria. They need to be conveniently relocated and comforted by a minimal number of caregivers. This category may comprise the largest percentage of patients at the scene. A small percentage of the remainder are in extremis or agonal. They are termed “expectant,” and cannot be helped other than to allow them to die with a minimum of discomfort and as much dignity as can be provided under the circumstances. The remainder are “priority,” and they all need transport to an MTF. These patients are bleeding, have airway problems, head injuries, burns, chest or abdominal pain, or evidence of spine or long-bone fracture. This latter category may represent only 20% of the casualties, but it is the most important.
Principles of triage3 that must be understood include the fact that patients are triaged and re-triaged, not only at all levels of patient care, but also within levels of patient care. The triage officer does not treat, assuming there is more than one caregiver present. The triage officer only sorts patients according to injury and probable outcome. The latter is dependent on available resources—time, personnel, and equipment—and their presumed efficient use. Weather, communications, and available transportation will all play critical roles in determining anticipated outcome. Assuming that explosive ordinance, radiation, and chemical threats have been eliminated, but a biological agent has not, what steps should be taken by the first responder or caregiver present at the scene of an ACT?4
At present, there are five specific agents considered likely sources of bioterrorism. They have several general characteristics in common that make them preferable to alternative agents. These characteristics include relative ease of production, packaging, transport, and delivery, as well as not only lethality, but also morbidity. Agents that kill rapidly may be less inducive of panic and terror than those that cause large numbers to be extremely ill for prolonged periods of time, their condition apparently communicable. The five agents most commonly cited, as potential threats, are those associated with anthrax, smallpox, botulism, plague, and tularemia. The characteristics of each will be presented with emphasis placed on detection, diagnosis, treatment, precautions, prophylaxis, quarantine, decontamination, and necrology (Tables 1,2, and 3). Other less likely agents, such as the encephalitides, the Ebola virus, and so on, will be mentioned, but only in passing, because of their much lower probability of encounter.
Table 1 Five Most Frequently Cited Bioterrorism Agents: Characteristics, Associated Disease, Recognition, and Identification
Table 2 Five Most Frequently Cited Bioterrorism Agents: Treatment, Prevention, Cause of Death, and Necrology
Table 3 Five Most Frequently Cited Bioterrorism Agents: Prophylaxis, Infection Control, and Decontamination
Anthrax5 has a long history as a disease among animals, but is much less commonly encountered in humans. Spores of Bacillus anthracis have been weaponized by the governments of many countries and individuals have been exposed accidentally in Russia as well as targeted by attacks in Japan and more recently the United States. While the number of deaths from these exposures is relatively small, the potential is impressive. The World Health Organization (WHO) estimated that aerial release of 50 kg of anthrax spores over an urban population of 5 million, would cause 250,000 casualties, almost half of whom would die without treatment. Similar scenarios have compared an aerosolized attack with anthrax spores to the effects of a hydrogen bomb attack on a large city.
Three forms of anthrax infection delivery occur in humans: inhalation, cutaneous, and gastrointestinal. Anthrax spores are 1.0 mcm, extremely hardy, and, when aerosolized, odorless, tasteless, colorless, and invisible. Obviously bioterrorists would most likely attempt inhalation exposure via an aerosolized release of spores from an aerial source. A two-stage illness ensues. In the primary phase, which lasts hours to days, the victim experiences fever, dyspnea, cough, headache, nausea, vomiting, chills, weakness, and pain in the chest and abdomen within days to weeks of exposure, depending on number and size of spores inhaled. The second phase begins with an abrupt increase in severity of symptoms, which coincides with massive lymphadenopathy, bacteremia, hypotension, and death, if untreated. The massive hilar lymphadenopathy presents radiographically as a “widened mediastinum.” Mediastinitis, meningitis, and cyanosis are common in the second phase. Clues to the diagnosis are the sudden appearance, in large numbers, of previously healthy city dwellers with an overwhelming flu-like illness. Differential diagnosis includes pneumonic plague. Treatment includes parenteral antibiotics (penicillin, etc.), ventilator and pressors if patients can be hospitalized, and if not, oral antibiotics. Blood cultures before antibiotic therapy are confirmatory, but case fatality rates approach 80% and most of those occur within the first 2 days of symptoms.
Prophylaxis consists of vaccination (six-dose series),6 which has been administered to all U.S. service personnel. Since there is no threat of patient-to-patient transmission of anthrax, patient contacts do not require treatment; however, the dead should be cremated because of spore hardiness. Decontamination of all suspected victims of inhalation anthrax is necessary to avoid secondary aerosolization of spores that remain on clothing, etc. Health care workers must wash their hands after contact with anthrax victims for the same reason.
