Handbook of Clinical Anesthesia
Hurricane Katrina, 9/11, the Sago mine, and severe acute respiratory syndrome (SARS) have entered our national consciousness and connote vivid images of tragic circumstances (Murray MJ: Disaster preparedness and weapons of mass destruction. In Clinical Anesthesia. Edited by Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC. Philadelphia: Lippincott Williams & Wilkins, 2009, pp 1559–1578). The term mass casualty refers to a large number of injuries or deaths that occur in a short period of time and have the potential to exceed the capabilities of local facilities. Mass casualty incidents include naturally occurring as well as intentional or unintentional events (Table 60-1).
- The Joint Commission
After the events of September 11, 2001, and the subsequent anthrax attacks, The Joint Commission (previously the Joint Commission on Accreditation of Healthcare Organizations) published a “white paper” to help hospitals develop systems to create and sustain community-wide emergency preparedness (Table 60-2). Ever-increasing demands on an underfunded health care system may limit the surge capacity to handle major emergencies (Fig. 60-1).
- Disaster Preparedness
Although the critical importance of planning and preparing to deal with the use of weapons of mass destruction is recognized, the reality is that we are far more likely to have to manage patients and health care facilities that are victims of natural and unintentional disasters (see Table 60-1).
Table 60-1 Disasters That May Result in Mass Casualties
Table 60-2 Disaster Preparedness and Response
Figure 60-1. SNF: Skilled Nursing Facility. Published with permission: Nathaniel Hupert, MD, MPH, “Addressing Surge Capacity in a Mass Casualty Event” Web Conference, broadcast on October 26, 2004. Agency for Healthcare Research and Quality, Rockville, MD. Available at http://www.ahrq.gov/news/ulp/btsurgemass/
- Role of Government
- The initial response to any disaster, whether natural, unintended, or terrorist initiated, begins at the local level and would involve law enforcement agencies (especially if criminal activity is suspected), firefighters, and paramedics.
- If the event supersedes the state's ability to respond, the federal government would become involved. The Federal Emergency Management Agency is the lead agency for assistance to state and local governments.
- Physicians who wish to volunteer can become members of the National Disaster Medical System.
- The Centers for Disease Control and Prevention has established a National Pharmaceutical Stockpile program as a national repository of antibiotics, chemical antidotes, life support medications, intravenous administration and airway maintenance supplies, and medical and surgical items.
- Role of Anesthesiologists in Managing Mass Casualties.It is difficult to anticipate every measure in which anesthesiologists could be asked to assist in managing mass
casualty situations. However, they are invaluable because of their basic understanding of physiology and pharmacology, airway skills, fluid resuscitation expertise, and ability to manage ventilators and provide anesthesia in the field environment, emergency department, operating room, and intensive care unit.
Table 60-3 Nuclear Accidents in Decreasing Order of Probability
III. Nuclear Accidents (Table 60-3)
- Radiation Injury.The experience from Chernobyl indicates the kind of injuries and results that anesthesiologists can anticipate from nuclear accidents, including radiation burns, bone marrow suppression, the destruction of the lining of the gastrointestinal (GI) tract, GI bleeding with translocation of bacteria, infection, sepsis, septic shock, and death.
- Potassium iodide is indicated to protect the thyroid gland from taking up 131I, and other drugs, such as 5-androstenediol, are being considered.
- Because of the possibility of exposure to ionizing radiation (such as from nuclear power plants), the American Academy of Pediatrics has recommended that at least two tablets of potassium iodide be available for all inhabitants within 16 km of any nuclear power plant.
- Potential Sources of Ionizing Radiation Exposure
- The greatest concern is the exposure to ionizing radiation that is unintentional as occurred at the Chernobyl nuclear power plants or exposure that is intentional.
- Exposure to ionizing radiation may be the result of terrorism. (A radiologic dispersion device remains the most likely cause of the event.)
- Individuals should be familiar with the types
of ionizing radiation (Table 60-4).
Table 60-4 Types of Radiation
- The most likely injury from ionizing radiation is to the tissues that have the greatest turnover rate (greatest for lymphoid tissue).
- Thrombocytopenia, granulocytopenia, and GI injury lead to bleeding and bacterial translocation across the GI epithelium. The net results are sepsis and bleeding—the hallmarks of acute radiation syndrome—which lead to death.
- Because ionizing radiation is invisible, individuals may appear normal or may present with nausea, vomiting, diarrhea, fever, hypotension, erythema, and central nervous system (CNS) dysfunction.
- Patients who present with nausea, vomiting, diarrhea, and fever are likely to have severe acute radiation syndrome. Hypotension, erythema, and CNS dysfunction manifest later.
- Long-term effects include thyroid cancer and psychologic injury as have been documented many times in the past.
- Depending on the type of radiation event, the first step is immediate evacuation of the area.
- The principle of disaster management always involves containment (bringing patients with material emitting ionizing radiation to the hospital should be avoided). To the extent possible, patients should be decontaminated at the site.
- Potassium iodide can prevent radiation-induced thyroid effects. (It should be given with 24 hours.)
- Acute radiation syndrome manifests as bleeding and sepsis.
- Biologic Disasters
Anesthesiologists need to be familiar with contagious diseases that are not initiated by terrorist groups (influenza, SARS, West Nile virus). Influenza has killed more people in the 20th century than has any other infectious disease.
- Influenza.Only subtypes of influenza A virus normally infect people (and birds, who are natural hosts). A new pathogenic virus is usually detected several months in advance of major outbreaks, but vaccines remain in short supply principally because of manufacturing liability issues. Antiviral drugs have some benefit in treating patients with flu, but development of resistance is a concern. Isolation and quarantine practices are effective, low-cost methods.
- Severe acute respiratory syndromeis caused by coronavirus, and health care workers are at risk because they often manage these patients. (The virus is airborne, and protective masks are indicated.) Strict quarantine prevents the spread of SARS.
- Biologic Terrorism
The ideal biologic agent is one that has the greatest potential for adverse public health impact, generating mass casualties and with the potential for easy large-scale dissemination that could cause mass hysteria and civil disruption. There are three categories of biologic weapons (Table 60-5). Category A includes weapons that are highly contagious and fit all the characteristics of a relatively ideal biologic agent.
- Smallpox(Table 60-6). Routine vaccination for smallpox was discontinued in the United States in 1972. It is precisely because of this that we are at most risk for terrorists using smallpox as a biologic weapon.
- Anthraxhas appeal as a bioterrorism agent because it can be “weaponized” (aerosolized). The three primary
types of anthrax infection are cutaneous, inhalation, and GI. Ninety-five percent of cases are cutaneous. Inhalation anthrax is hard to detect and manifests as an influenza-like disease with fever, myalgias, malaise, and a nonproductive cough with or without chest pain.
Table 60-5 Biologic Agents Used for Warfare
- The most notable finding on physical examination and laboratory and imaging testing is a widened mediastinum. When a patient develops profound dyspnea, death usually ensues within 1 to 2 days.
- In the past, penicillin G was the treatment of choice, but because weaponized anthrax has been engineered to be resistant to penicillin G, ciprofloxacin or doxycycline is more commonly used.
- Plague(bubonic and pneumonic). The virus has a 2- to 6-day incubation period at which time there is a sudden onset of fever, chills, weakness, and headache. Without treatment, patients become septic and develop septic shock with cyanosis and gangrene
in peripheral tissues, leading to the “black death” descriptor that was used during the epidemics in Europe.
Table 60-6 Comparison of Smallpox and Chickenpox
- The treatment of choice is streptomycin, but chloramphenicol and tetracycline are acceptable alternatives.
- Because the respiratory secretions are highly infectious, patients with pneumonic plague should be managed as one would manage patients with drug resistance to tuberculosis.
- Tularemia.Normally, humans acquire tularemia from direct contact with an infected animal or from the bite of an infected tick or deerfly. The virus has a 3- to 5-day incubation period, and then the onset of disease is marked by fever, pharyngitis, bronchitis, pneumonia, pleuritis, and hilar lymphadenopathy. Prophylaxis with streptomycin, ciprofloxacin, or doxycycline has been recommended.
- Botulismis a neuroparalytic disease caused by the toxin Botulinum, the most potent poison known. Victims develop progressive weakness and a flaccid paralysis that begins in the extremities and progresses until the respiratory muscles are paralyzed. Patients with profound respiratory impairment should have their tracheas protected and mechanical ventilation initiated.
- Hemorrhagic Fevers.At least 18 viruses cause human hemorrhagic fevers, which form a special group of viruses characterized by viral replication in lymphoid cells. Infected individuals develop fever and myalgia, evidence of capillary leak (peripheral or pulmonary edema), disseminated intravascular coagulation, and thrombocytopenia. There are no specific antiviral therapies for this class of viruses.
- Role of Anesthesiologists in Bioterrorism.Airway management and ventilator management may be critical, as are the establishment of intravascular access and volume resuscitation. Anesthesiologists must protect themselves by using 100% effective respiratory protection, going so far as to consider an oxygen-rebreathing system.
- Chemical (Table 60-7)
- Nerve agents are chemicals that affect nerve transmission by inhibiting acetylcholinesterase so that acetylcholine accumulates at the muscarinic and nicotinic acetylcholine receptor and within the CNS.
Table 60-7 Types of Chemical Agents
- Nicotinic stimulation leads to tachycardia and hypertension at the preganglionic site and at the nicotinic acetylcholine receptor on the neuromuscular junction. Signs and symptoms include fasciculations, twitching, fatigue, and flaccid paralysis.
- Excess parasympathetic activity leads to miosis and loss of accommodation, so patients complain of blurred vision.
- Within the respiratory system, the increased parasympathetic activity leads to bronchospasm, dyspnea, and rhinorrhea.
- Within the cardiovascular system, activity within the muscarinic system leads to bradycardia. Activity within the nicotinic site leads to preganglionic nodes and increases in heart rate.
- Treatment for nerve agent poisoning is with atropine, pralidoxime chloride (2-PAM-Cl) (a continuous infusion may be used), or both.
- The US military travels with automatic injectors containing 2 mg of atropine and 600 mg of 2-PAM-Cl.
- For situations in which one is anticipating nerve agent exposure, pyridostigmine may be used. It is a long-acting agent that binds with acetylcholinesterase, allowing the enzyme to spontaneously regenerate. It does not cross the blood–brain barrier and must be taken more than 30 minutes before exposure.
- Patients are decontaminated by removing their clothing and washing with copious amounts of water in 5% hypochlorite (household bleach).
- Pulmonary agentsinclude chloropicrin (PS), chlorine (CL), phosgene (CG), diphosgene (DP), and Ricin.
- Phosgene is a prototypical agent because it is deadlier than any of the other compounds. It is a colorless gas and has an odor of recently cut hay at 22° to 28°C and normal pressure conditions.
- Phosgene is highly soluble in lipids, so it can easily penetrate the pulmonary epithelium and the cells lining the alveoli.
- Although it is very lipid soluble, phosgene reacts rapidly with water, forming hydrochloric acid (it is extremely toxic to tissues, causing acute respiratory distress syndrome) and carbon dioxide.
- For individuals who are exposed, gas masks provide the best protection.
- Blood agents(cyanogens) are inhaled and release hydrogen cyanide, which impairs cytochrome oxidase and aerobic metabolism at the level of the mitochondria (metabolic acidosis).
- The blood agents are hydrogen cyanide (AC), hydrocyanic acid (HCN), cyanogen chloride (CK), and arsine (SA).
- Hydrogen cyanide is a colorless liquid that can be taken up through the skin as a liquid or inhaled.
- Treatment for cyanide toxicity involves the administration of sodium thiosulfate with supportive care in terms of tracheal intubation, ventilation, 100% oxygen, and cardiac support with inotropes and vasopressors. (Nitroprusside is a medical cause of cyanide toxicity.)
- Sodium mustard and related compounds, such as nitrogen mustard, phosgene oxime, and lewisite, also known as “blister agents,” get their names by the fact that with contact with skin, these compounds produce burns and blisters. Although these are the most readily apparently manifestations, these compounds are also inhaled and can inflict severe damage to the respiratory system and eyes and can also produce multiple organ dysfunction syndrome.
- Blister agents are colorless and almost odorless. If the temperature is high enough, odor is present, which smells like rotten onions or mustard.
- Individuals loose their sight, and nausea, vomiting, and diarrhea develop along with severe respiratory difficulty. (The effects seen on the skin can also happen in the pulmonary epithelium.)
- A nuclear–biologic–chemical protective suit and gas mask provide the best protection.