Ira J. Blumen
Christine A. Babcock
HIGH-YIELD FACTS
• Ionizing radiation is more dangerous than nonionizing radiation because such reactions lead to breaks in both DNA and RNA.
• There are two categories of radiation injuries with which the emergency physician should be familiar:
• Exposure injury, which generally represents no threat to emergency care providers.
• Contamination, which may represent a risk to emergency personnel.
• Acute radiation syndrome may develop following a whole-body exposure of 100 rad or more that occurs over a relatively short period of time.
• Total-body irradiation with >1000 rad results in a neurovascular syndrome.
• In the presence of contamination, if the patient’s condition permits, decontamination should begin in the prehospital setting.
Radiation accidents involving discarded medical and industrial sources get little attention compared to problems at nuclear power plants or weapon facilities. Unfortunately, these accidents occur around the world with surprising regularity and, in some instances, prove deadly.
According to the Radiation Emergency Assistance Center/Training Site (REAC/TS) Radiation Accident Registry, between 1944 and 2007, there have been 432 accidents worldwide. These accidents resulted in significant radiation exposure to 3082 individuals and in 127 deaths (Table 142-1).
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TABLE 142-1 |
Major Radiation Accidents: Human Experience—1944 to June 2007 |
Despite the relatively rare incidence of medically significant pediatric radiation accidents, our dependence on nuclear energy makes it necessary for today’s emergency physician to understand its potential for disaster. Most obvious are the threats of sophisticated nuclear weaponry to individuals of all ages. A more probable predicament, however, is an isolated or limited exposure in a medical, industrial, or research accident, or during the transport of radionucleotides. Basic preparation for radiation emergencies is not difficult, but a thorough understanding of the pathophysiology and clinical presentation is necessary in order to successfully handle all aspects of these complex problems.
All individuals are susceptible to radiation injury if the exposure is of significant dose and duration. Children, however, may suffer greater, short-, and long-term consequences of a significant radiation exposure for several reasons. Children are more susceptible to relatively greater internal exposure to inhaled radioactive gases given disproportionately higher minute ventilation.1 They are also at greater risk for developing subsequent malignancies when they are exposed to radiation.2,3 In the event of nuclear fallout, the short stature of children increases their exposure to a higher concentration of radioactive material on the ground.1 In addition, children are more likely than adults to experience psychological trauma leading to enduring psychological injury after a radiation disaster.1,4
TYPES OF RADIATION
Radiation is a general term used to describe energy that is emitted from a source and results in the transfer of energy through space. The term encompasses the broad-wavelength microwave and extends through the ultrahigh-frequency γ-rays. A radioactive substance, referred to as a radioisotope or radionucleotide, gives off radiation. A person exposed to external or remote radiation has been irradiated but does not become radioactive. The victim may give off radiation only if there was external or internal contamination caused by the presence of radioactive particles (α and β).
Radiation can be classified as either ionizing or nonionizing. In addition, radiation can be described either as nonparticulate (electromagnetic) or particulate. Electromagnetic radiation has no mass and no charge. It occurs in waveforms and is described by wavelengths. Examples of this nonparticulate/electromagnetic radiation can be found in both the ionizing and nonionizing radiation classifications. In contrast, particulate radiation has mass and can either be charged or uncharged ionizing radiation.
NONIONIZING RADIATION
Nonionizing radiation is relatively low energy in nature and does NOT result in acute radiation injuries or contamination. The adverse effects to humans are limited to local heat production. A classic example of the effects of nonionizing radiation in humans is sunburn. In order of decreasing energy content, the nonionizing forms of radiation include ultraviolet rays, visible light, infrared radiation, microwaves, and radio waves. These types of radiation are easily shielded by protective barriers (e.g., sunscreen) and do not result in contamination or penetration of human tissue. These forms of nonionizing radiation also represent many of the electromagnetic radiations. Their energy content is less than that of ionizing radiation, making them a less threatening form of radiation (Table 142-2).
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TABLE 142-2 |
Types of Radiation |
IONIZING RADIATION
Ionizing radiation is named for its ability to interact with matter. Types of ionizing radiation include α-particles, β-particles, and neutrons, which represent particulate radiation (has mass); and x-rays and γ-rays, which are nonparticulate forms of radiation (has no mass).
Ionizing radiation is more dangerous than nonionizing radiation because such reactions lead to breaks in both DNA and RNA, damaging important biologic functions at the cellular metabolic level. Anomalies may be passed on to subsequent offspring or they may result in cell death or the inability to replicate. Ionized radiation has a high frequency, a short wavelength, and a billion times more energy than nonionizing radiation. Common sources of ionizing radiation are nuclear reactors, nuclear weapons, radioactive material, and radiography equipment. Material identified by the label radioactive produces ionizing radiation.
Nonparticulate Radiation γ-Rays have the highest energy content of the nonparticulate and massless radiations. Their photon radiation originates in the atomic nucleus. They can penetrate deep into the tissue, depositing energy and interacting with the various layers they penetrate. Constant low-level exposure through cosmic radiation is a usual source. γ-Radiation is a common cause of acute radiation syndrome due to radioisotope decay and radiation from linear accelerators. A lead shield, 1 to 2 cm in depth or thick concrete, would provide satisfactory protection from γ-rays.
X-rays have the next highest energy content of the nonparticulate, massless radiations. Unlike the γ-ray, which is produced within the nucleus of the atom, x-rays originate from outside the nucleus and are emitted by excited electrons. Like the γ-ray, x-rays can also penetrate tissue and deposit energy deep within the cells, are shielded by lead, and can be detected with a Geiger counter. Their usual source is medical or industrial in nature.
Particulate Radiation α-Particles are composed of two protons and two neutrons and possess a 2+ electrical charge. They originate from the nucleus of the atom and, being relatively heavy radioactive emissions, can travel only inches from their source. In general, they cannot penetrate paper or epidermis because of their mass and size and are rarely harmful externally. Examples include plutonium, uranium, and radium. α-Particles can emit significant amounts of radiation and cannot be detected with standard Geiger counters.
β-Particles have a small mass, composed of a single electron emitted from the atom’s nucleus, and possess a 1 charge. They can disperse only a few feet from their source and penetrate tissues only a small amount (up to 8 mm), primarily causing thermal injuries. Clothing alone can often provide adequate protection from β-particles. Despite their inability to penetrate the skin to any significant depth, both α- and β-particles can be harmful if they are ingested or inhaled or if wounds are contaminated by these particles. The common research isotope tritium is an example, as is carbon14 and phosphorous.
Neutrons are the third type of particulate radiation. Without an electrical charge, they ionize by colliding with atomic nuclei within cells and tissues. They possess strong power to penetrate and represent the only form of radiation that can make previously stable atoms within the body radioactive. They can be more damaging than x-rays or γ-rays and are responsible for radioactive fallout. Emitted only after nuclear detonation, nuclear reactors, weapons, and accelerators are common sources of neutron radiation. Specialized concrete is necessary to provide shielding from neutron radiation.
MEASURING RADIATION
Although radiation cannot be sensed by the human body, it can be detected and quantified by dosimeters or Geiger–Mueller tubes at levels far below those that result in any biologic significance. There are several units of measurement used in relation to radiation: roentgen is the unit of measurement used during the production of x-rays that measure the ion pairs produced in a given volume of air; doserepresents the amount of energy deposited by radiation per unit of mass; and the rad (roentgen absorbed dose) is the basic unit of measurement. A rad can be defined as a unit of absorbed dose of radiant energy that is equal to 100 erg of energy deposited per gram of absorbing material. The gray (Gy) represents the standard international (SI) unit for dose:
1 Gy = 100 rad
1 cGy = 1 rad
Units of rem (roentgen equivalent in man) represent a calculated radiation unit of dose equivalent. The absorbed dose (rad) is multiplied by a factor to account for the relative biologic effectiveness (RBE) of the various types of radiation:
rem = rad × RBE.
β-particles, x-rays, and γ-rays have an RBE of 1 and for these sources of radiation 1 rad = 1 rem. The RBE for α-particles and neutrons is 20 and, therefore, 1 rad = 20 rem for these sources of radiation.
The sievert (Sv) is the SI unit for dose equivalent, where
1 Sv = 100 rem
1 cSv = 1 rem
Therefore, 1 Gy = 100 rad = 100 rem = 1 Sv. Generally, the terms rem and mrem (millirem) are used when they refer to the exposure of biologic systems.
RADIATION EXPOSURE
The clinical impact of radiation exposure depends on several factors. These factors are also important to properly coordinate the safety of both prehospital and hospital providers who may respond to a radiation incident.
The clinical effects of radiation exposure are related to the type of radiation involved, the amount of radiation, and the nature of the exposure (continuous or intermittent). In addition, the harmful effects of ionizing radiation may be affected by the total time of the exposure, the distance from the radiation source, and the presence of any shielding (amount and type).
A radiation exposure over a prolonged period of time is less likely to be harmful to an individual than the same dose over a shorter time period. For example, an exposure of 100 rem in 1 second will be more harmful than an exposure of 100 rem over 1 year.
There is an inverse square relationship between distance from a radiation source and the resultant exposure, making increased distance an effective means to reduce the amount of exposure. An exposure can be reduced by a factor of 4 simply by doubling the distance from the radiation source. Tripling the distance will decrease the exposure by a factor of 9.
Shielding may be an effective method to reduce radiation exposure when one is dealing with low-energy radiation (x-rays). When dealing with medium- or high-energy radiation, shielding may become impractical due to the amount of lead or concrete that would be necessary.
In the United States, there are natural and technological radiation sources to which children and adults are commonly exposed (Fig. 142-1). Background radiation may represent an exposure between 300 and 360 mrem/y. Radon accounts for the largest amount of this background radiation (∼200 mrem/y). Consumer products (10 mrem/y), cosmic radiation (26 mrem/y), terrestrial radiation (28 mrem/y), nuclear medicine (14 mrem/y), other medical sources (39 mrem/y), and internal sources (40 mrem/y) account for the balance.5
FIGURE 142-1. Common sources of natural and technological radiation exposure in the United States.
Technological sources of radiation may represent a wide range of exposures to individuals. Color television may result in an exposure of 1 mrem/y; a round-trip, coast-to-coast jet flight may result in a 2- to 5-mrem exposure; and a chest x-ray causes an exposure between 5 and 10 mrem. The common radiation exposure to a patient during angiography may be 1000 mrem. As technology changes and new technologies are developed, we are likely to encounter additional sources of radiation in varying amounts.
RADIATION INJURIES
There are two categories of radiation injuries with which the emergency physician should be familiar. The first type is an exposure injury, which generally represents no threat to emergency care providers. Contamination, the second type of radiation injury, may represent a potential risk to emergency personnel.
EXPOSURE
Exposure radiation injuries can be classified into two categories. A person may be the victim of a localized radiation injury or may have suffered a whole-body exposure.
Localized Radiation Injuries A large dose of radiation exposure to a small part of the body will result in a local (partial-body) radiation injury. These injuries often occur over months or even years, but they may occur over a shorter amount of time.6
Localized radiation injuries most commonly affect the hand/upper extremities, with the buttocks and thighs representing the next most common sites. Adults and children may unknowingly come into contact with a radiation source by handling an unknown object and putting it into their pockets. Typically, these injuries occur in the occupational setting. Localized radiation accidents may also result from an inadvertent exposure to an intense radiation beam.
The dose of radiation that can result in a local radiation injury varies greatly. Larger doses are often better tolerated than a whole-body exposure. Accidental exposures from radioactive sources with a surface dose of nearly 20,000 rad/min have been reported to have caused localized radiation injuries.
The initial clinical picture of a localized radiation injury depicts a thermal injury to the skin. While thermal burns develop soon after an exposure, erythema from a local radiation injury is delayed.7 Radiation injury should be considered in the differential diagnosis for any patient who presents with a painless “burn,” but who does not remember a thermal or chemical insult.
Prolonged radiation exposure causes blood vessel fibrosis, leading to tissue necrosis. The outcome will be determined by the degree of blood vessel and tissue damage. Classification of these localized injuries can be divided into four types, differentiated by increasing epidermal and dermal injury. They are summarized in Table 142-3.
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TABLE 142-3 |
Localized Radiation Injuries |
Pediatric gonads and eyes are very sensitive to radiation exposure. Depression of spermatogenesis8 and destruction of oocytes may occur.9 In addition, low doses of radiation may induce premature cataract formation.10
Whole-Body Exposure Acute radiation syndrome may develop following a whole-body exposure of 100 rad or more that occurs over a relatively short period of time. Organ systems with rapidly dividing cells (bone marrow and gastrointestinal tract) are the most vulnerable to radiation injury. With greater doses of radiation, however, all organ systems may become involved, including the central nervous system.11
Estimating the exposure (in rads) of a whole-body radiation victim may be difficult when the patient presents to the emergency department. Dosimeters and Geiger counters are not standard equipment in many emergency departments and are often only able to identify radioactive contamination. Therefore, they are often of little help in determining the total radiation dose or duration of exposure. A mechanical dosimetry-monitoring device worn by the victim during the time of exposure would be helpful but is rarely available. Instead, the emergency physician’s history and physical examination, along with baseline laboratory values, are essential in estimating the whole-body exposure. This technique is referred to as biologic dosimetry. For this purpose, the primary indicators include the time of onset of symptoms and depression of absolute lymphocyte count. The earlier signs and symptoms develop, the higher the dose of radiation exposure and the worse the prognosis. Table 142-4 identifies characteristic signs and symptoms with the radiation dose that can be anticipated following a whole-body exposure. A biologic dosimetry calculator is also available as a resource to clinicians through the Radiation Event Medical Management Website (http://www.remm.nlm.gov/ars_wbd.htm) maintained by the United States Department of Health and Human Services. The gold standard of radiation biodosimetry is cytogenetic biodosimetry, which identifies chromosomal aberrations. In the United States, this type of measurement is only available through the Armed Forces Radiobiology Research Institute (AFFRI) and REAC/TS. Consequently, the clinical symptoms and lymphocyte counts will still be the mainstay parameters for biologic dosimetry.
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TABLE 142-4 |
Biological Dosimetry |
A progressive sequence of signs and symptoms following a whole-body exposure can be divided into four phases: prodromal (0–2 days), latent (2–20 days), manifest illness (21–60 days), and recovery or death.11
An individual’s susceptibility and the dose of radiation, dose rate, and dose distribution will dictate the onset, duration, and character of symptoms in a predictable representation. The prodromal stage can begin within minutes to hours after exposure and is dose dependent. The most common symptoms of this stage include nausea, vomiting, and diarrhea due to sloughing of the gastrointestinal epithelium. Patients may also complain of apathy, palpitations or fever. Exposure to <100 rad rarely causes symptoms and patients who do not exhibit nausea or vomiting within 6 hours of a radiation accident are unlikely to have been subject to a significant whole-body exposure. Prodromal markers beginning within 6 hours suggest an exposure in excess of 100 rad. For example, symptoms that present within 2 hours of exposure usually indicate a >200 rad and potentially lethal exposure. Higher doses will result in a more rapid onset of these initial signs and symptoms, probably due to acute tissue injury and the subsequent release of vasoactive substances, including histamine and bradykinin.
A lower-dose exposure will yield a resolution of the prodromal symptoms over a period of days to weeks, during the latent stage. The latent phase is asymptomatic, typically occurring between 2 and 20 days after the initial exposure. Progressively higher radiation doses will prolong the prodromal stage while limiting the latent period until a point is reached when it appears that the prodromal stage proceeds directly to the manifest illness stage without any resolution of the prodromal symptoms. The duration of the latent phase is inversely related to the dose of the radiation received.
During the manifest illness stage, specific organ systems are affected and the patient is at the greatest risk for infection and bleeding. Three syndromes may develop during this stage, depending on the total amount of radiation exposure: the hematopoietic syndrome (220–600 rad), the gastrointestinal syndrome (600–1000 rad), and the neurovascular syndrome (>1000 rad).
Although all cell lines in the hematopoietic system are affected by radiation, the absolute lymphocyte count represents the best way to estimate exposure hematologically.12 Leukocyte counts may be elevated initially because of demargination, but the lymphocyte portion of the differential will quickly start to decrease. The lymphocyte count at 48 hours can approximate the radiation dose and prognosis. A lymphocyte count >1200/mm3 indicates a 100- to 200-rad exposure and most often a good prognosis. An absolute lymphocyte count of 300 to 1200/mm3 suggests a 200- to 400-rad exposure, which promises a fair outcome. Exposure to >400 rad is marked by a poor prognosis and is expected with lymphocyte counts <300/mm3. Neutropenia, thrombocytopenia, and anemia may develop after a latent period lasting a few days to 3 weeks. The patient will subsequently suffer from dyspnea, malaise, purpura, bleeding, and opportunistic infection (Fig. 142-2).
FIGURE 142-2. A 48-hour check of the absolute lymphocyte count suggesting the severity of the exposure to radiation. Good prognosis: a lymphocyte count greater than 1200/mm3. A 100- to 200-rad exposure. Fair prognosis: an absolute lymphocyte count of 300 to 1200/mm3. A 200- to 400-rad exposure. Poor prognosis: lymphocyte count below 300/mm3. More than 400-rad exposure.
Gastrointestinal illness will be most evident with total-body exposures of 600 to 1000 rad. The prodromal phase is abrupt and is marked by severe vomiting and diarrhea. The latent stage may be quite short and is followed by continued GI symptoms, leading to relentless fluid loss, fever, and prostration. The radiosensitive mucosal cells of the small bowel begin to slough, which, combined with the coexistent hematopoietic abnormalities, produces severe, bloody diarrhea. In addition, the disrupted mucosal barrier allows bacteria to enter the circulation and combined with neutropenia may result in severe sepsis. Even with intense supportive care, the patient rarely survives.13
Total-body irradiation with >1000 rad results in a neurovascular syndrome. At such high radiation levels, even cells that are relatively resistant to injury are damaged. Ataxia and confusion quickly develop and there is direct vascular damage, with resultant circulatory collapse.13 The patient usually expires within hours.
Patients with lower levels of exposure and those patients fortunate enough to respond to aggressive supportive management will likely recover. Further management is guided by specific organ system insults. For survivors, the long-term risks of exposure to ionizing radiation include cataracts, leukemia, and development of carcinomas. It should be noted that the median lethal dose of total-body irradiation is estimated at 400 rad (Table 142-5).
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TABLE 142-5 |
Whole-Body Exposure |
CONTAMINATION
Contamination is the second type of radiation accident. Radioactive particles, solid or liquid, are deposited and may remain on the surface of the victim, resulting in an external contamination. External contamination rarely causes significant medical problems to the patient. Internal contamination may be the result of inhaled, ingested, or absorbed radioactive particles. Neutrons, β-particles, and α-particles are most commonly responsible for contamination and are more difficult to eliminate and potentially more serious in children. Unlike an exposure victim, the contaminated patient does represent an additional challenge and potential risk to hospital and prehospital personnel.
In most situations, if the patient’s condition permits, decontamination should begin in the prehospital setting. This will reduce the potential spread of radioactive material and will decrease the potential contamination of hospital workers or other rescuers. Fortunately, if appropriate management steps are taken, the radiation-contaminated patient should present little danger to hospital staff, even if decontamination was incomplete prior to arrival at the hospital.
MANAGEMENT
There are no acute, life-threatening complications of a survivable radiation injury that require immediate intervention. Emergency treatment should be supportive and directed toward the prevention of complications.
It will be important to determine, quickly, whether the patients are victims of a radiation exposure or a contamination. Radiation contamination requires that decontamination begin promptly after stabilization. The radiation exposure patient who is not contaminated represents no danger to the hospital staff or other patients. These victims can be managed in the emergency department and require no immediate intervention related to the radiation exposure.
At all times, there must be a proper balance between patient care and the personal safety of rescuers and healthcare workers. Appropriate measures must be taken by both prehospital and hospital personnel to minimize their risk of exposure while managing either life-threatening injuries or the decontamination of the patients they serve. While both prehospital and hospital workers may be at risk, it is the prehospital personnel and other rescuers responding to the site of a radiation accident, who are more often exposed to significant radiation. A threshold of 5000 mrem (5 rem) should be the exposure limit, except to save a life. A once-in-a-lifetime exposure to 100,000 mrem (100 rem) to save a life has been established by the National Council on Radiation Protection as acceptable and will not result in any undue morbidity.
Hospital personnel are at a very low risk of significant radiation exposure when treating victims of a radiation accident. Off-site medical personnel who treated victims of the Three Mile Island and Chernobyl accidents were exposed to radiation doses of <14 mrem. The recent Fukushima Daiichi event resulted in release of large amounts of radioactive iodine and cesium into the environment. A 20-km radius was evacuated for a prolonged period of time and no deaths from acute radiation syndrome were reported. Levels of cesium in adults and children 6 months after the event are much lower than those reported in the Chernobyl accidents. However, the long-term effects of this event are not yet known.14
PREHOSPITAL MANAGEMENT
The history obtained by prehospital personnel is of paramount importance in management decisions regarding radiation victims. For internal exposure, the route of entry, type, and quantity of radioactive material should be determined. If the incident has occurred in an industrial or laboratory setting, initial decontamination procedures may be instituted by on-site personnel according to established protocols before EMS personnel arrive. A quick response in decontamination will limit the exposure to the victim and decrease the amount of further contamination of both the ambulance and the emergency department. For unstable patients, the minimal action performed prior to rapid transport is the removal of contaminated clothing.
After transport of the patient to the hospital, EMS personnel and their vehicles must be inspected for the presence of radioactive contamination before they leave the facility.
EMERGENCY DEPARTMENT MANAGEMENT
Few hospitals will be called on to treat victims of life-threatening radiation accidents. The exceptions are hospitals in close proximity to nuclear power plants or in the event of a nuclear war. It is more likely, however, that hospitals will be called on to attend victims of a minor industrial accident or an accident involving the transportation of radioactive materials. The end result will be a patient with “routine injuries,” whose treatment may be complicated by an inadvertent radiation exposure with or without low-level radioactive contamination.
RADIATION ACCIDENT PLAN
The Joint Commission requires each emergency department to have a radiation accident plan. In the event of a medically significant radiation accident, a well-prepared and practiced plan will supply emergency care providers with an appropriate knowledge base, management protocols, and additional resources that can be called upon.
A major part of a well-prepared plan facilitates the identification of significant versus perceived radiation danger. The incidence of significant radiation accidents may be rare for some hospitals, but the incidence of perceived radiation accidents may be much greater. A vehicular accident involving a truck or train carrying radioactive material near a school may send dozens (or hundreds) of anxious parents and their children to the emergency department. The staff of a well-prepared emergency department can assess the potential risks and, when appropriate, correct any misconceptions and ease the fears the general public may have.
A lack of experience, an incomplete knowledge base, and a significant degree of fear among healthcare providers often result in the mismanagement of radiation victims. Therefore, it is essential that an emergency department develop protocols for dealing with both the radiation exposure itself and the medical management of these victims. Protocols should be rehearsed and drilled until all staff members who may need to participate are familiar with the process and their anticipated responsibilities.
The final component of an emergency department’s resource plan for radiation emergencies is a list of “additional references.” These resources include local, state, regional, and/or national agencies and their 24-hour telephone numbers that can be called for information or assistance. The US Department of Energy is also available to coordinate a federal response and provide assistance through the radiological assistance program (RAP). RAP provides advice and radiological assistance to government agencies and to the private sector for incidents involving radioactive materials that pose a threat to the public health and safety or the environment. RAP can provide field deployable teams of health physics professionals equipped to conduct radiological monitoring and assessment. RAP is managed at eight regional coordinating offices across the country.
GENERAL PROCEDURES
Early notification of estimated time of arrival will allow the emergency department to implement its radiation accident plan and to advise EMS personnel on initial prehospital decontamination.
When exposed solely to irradiation from γ-rays, x-rays, β-particles, and, frequently, neutrons, patients do not become radioactive. However, the radiation accident plan must assume that there will be external contamination. Figure 142-3 outlines an example of many of the procedures and actions that should be addressed in the radiation accident plan.
FIGURE 142-3. Radiation accident plan: recommended emergency department procedures.
Separate contaminated and clean treatment areas must be established. When possible, prepare a separate entrance to the emergency department for radiation victims. The floor of the contaminated treatment area and the ambulance receiving area must be covered with plastic or paper sheets to prevent the spread of contamination. Devices must be immediately available to monitor both the patients and personnel for any evidence of radioactive contamination.
All personnel in the treatment area must wear protective clothing. This includes gowns, caps, masks, shoe covers, double gloves, and personal monitoring devices (film badges). If airborne contaminants are suspected, respirators must be worn. In most cases, decontamination begins during the prehospital stage, significantly reducing the risk of exposure to emergency department staff. Despite this, fear of contamination may persist in poorly educated or ill-prepared hospital personnel.
Separate staff members are assigned to the clean and contaminated treatment areas. Staff assigned to the contaminated areas are provided appropriate personal protective equipment. Medical staff should be designated for triage and initial resuscitation, which must take place before decontamination.
A radiation safety officer should be assigned to monitor the treatment area and everyone within. This officer is given a Geiger–Mueller counter for detecting β- and γ-radiation or a scintillation detector, which offers a higher sensitivity in detecting α-, β-, γ-, and neutron particles. This designated individual oversees the decontamination procedures, the routing of patients, and the movement of hospital personnel. This is important to ensure adequate decontamination and to prevent the unintentional spread of contamination.
Treatment protocols and priorities should be reviewed with assigned staff. Established mechanisms to minimize their exposure, while not compromising patient care, should be reinforced. Ideally, several medical personnel should be assigned to care for each contaminated patient. Individual exposure time can be decreased and a greater distance can be maintained from the patient when the health worker is not involved in direct decontamination or medical management. In cases of a highly radioactive contaminant or foreign body, a lead shield or apron is necessary to protect personnel. However, in most situations, lead aprons are not effective protection against the most common contaminant, the medium-energy γ-ray.
Patients enter the emergency department through a separate entrance where radiation detection equipment is in place. Patients on ambulance stretchers are transferred to clean hospital carts in the ambulance bay.
The ideal decontamination site is an isolated room designed with a closed drainage and ventilation system and fully equipped for a major resuscitation. In many hospitals, the morgue is the only available isolation room meeting these criteria. Alternatively, the route from the ambulance area can be to an outside decontamination area. Resuscitation equipment and other emergency supplies should be relocated to this site when the radiation accident plan is activated.
Management of immediate life-threatening injuries remains the first priority for these patients. Following resuscitation, the radiation victim is carefully evaluated to determine if there is any surface contamination or if there is the possibility of inhaled or ingested radioactive material.
All burns and open wounds must also be evaluated for contamination. They must be irrigated with copious amounts of water and examined for foreign bodies. Highly contaminated foreign bodies, while rare, may represent the greatest single hazard to hospital personnel. These contaminants must be removed from the victim as safely and quickly as possible. Radiation burns may be delayed in their presentation. They are managed in the same way as non–radiation-induced partial- and full-thickness burns. Extensive β-particle burns often result in full-thickness injury and require skin grafting.
Individuals not directly involved in the evaluation or treatment of radiation victims must be kept away from the designated treatment areas. Personnel assigned to either the clean or contaminated treatment areas must remain there. If it becomes necessary to move between the treatment areas, it should be done only after appropriate monitoring for contamination. Once the decontamination process for all victims has been completed, all participating hospital personnel must be reevaluated and decontaminated as needed. Their protective garments must be removed before they leave the treatment area and disposed of properly.
A baseline complete blood count, differential, electrolytes, and urinalysis should be obtained upon presentation. Patients who remain in the hospital should have a repeat CBC with differential drawn every 6 hours for a total of 48 hours and daily electrolytes and urinalysis with microscopy. Patients who exhibit a decrease in absolute lymphocyte count will have to have a type and crossmatch and human leukocyte antigen (HL-A) typing performed in the event that a bone-marrow transplant should become necessary.
If there is any evidence of infection, it should be treated in the same way as other infections. Severely neutropenic patients should receive broad-spectrum prophylactic antimicrobial agents. Prophylaxis should include a fluoroquinolone with streptococcal coverage or a fluoroquinolone without streptococcal coverage plus penicillin or amoxicillin, antiviral drugs, and antifungal agents.15
Not all radiation victims will require hospitalization although, in general, exposures >100 rad may warrant inpatient care. If radiation victims exhibit severe vomiting, thrombocytopenia, evidence of CNS symptom or have multiple trauma or severe burns they should be admitted. Reverse isolation measures are used for all documented exposures of 200 to 1000 rem and for those patients with absolute lymphocyte counts <1200/mm3 or 50% of the baseline value. Treatment with colony-stimulating factors should be considered for those at risk for developing neutropenia.11,16 For severely pancytopenic patients, stem cell transplantation is often necessary.17
In addition to the hematopoietic complications (infection and bleeding) that may be seen with whole-body radiation >200 to 600 rad, victims may develop significant fluid and electrolyte complications. Any indicated surgery must be performed without delay to avoid these additional problems.
Transfusion of selected blood products is based on the individual hematologic derangement encountered and should follow the usual guidelines for their use.
EXTERNAL CONTAMINATION
External contamination often presents a logistical problem for hospital workers. However, an organized radiation accident plan should facilitate both the logistical and medical management of these patients.18
Victims of radiation exposure who show no signs of injury and are otherwise healthy may be best served at designated decontaminated facilities. In general, hospital resources should be used for radiation victims who also require medical management.
The process of decontamination, or cleaning the patient of particulate radioactive debris, should be initiated as soon as possible following the event. Rescue personnel must wear protective clothing, including rubber gloves, shoe covers, masks, and film badges. This protective clothing does not reduce the exposure to penetrating radiation. Rather, it serves to prevent any radioactive particles from coming in contact with the personnel or their clothing and to facilitate cleanup and disposal.
Initially, any open wounds are covered, and the patient’s clothing is removed; all articles are placed in clearly labeled plastic bags. Up to 70% to 90% of external contamination can be eliminated by this action alone. Any open wound is considered contaminated until proven otherwise, and decontamination should precede the irrigation of intact skin surfaces. The skin is then washed with copious amounts of water and soap, with particular attention to skin folds, ears, and fingernails. Decontamination should proceed from areas of highest to lowest radioactivity. The use of damp washcloths with lukewarm water rather than rinsing with running water, may be more practical for some emergency departments. The disposal of contaminated washcloths in plastic bags may be easier than the collection of contaminated wash water. All wastes must be captured in sealed containers labeled “Radioactive Waste.”
Shaving of the patient’s hair is to be avoided, along with excessive rubbing of the skin. Both of these maneuvers cause an increased risk of transdermal uptake. Open, uncontaminated wounds are covered with sterile dressings, and contaminated wounds are then cleaned aggressively, similar to other dirty wounds.
Whenever possible, a dosimeter should be used to determine the completeness of the decontamination. The goal is to get the radiation level “as low as reasonably achievable”; this is commonly referred to as the ALARA principle. Metallic fragments and “hot” particles should be localized and removed by mechanical means.19 When dealing with an external contamination, it is important to prevent it from becoming an internal contamination.
INTERNAL CONTAMINATION
Radioactive particles that are ingested or inhaled or that contaminate open wounds can cause significant cellular damage. These particles will continue to irradiate tissues until they are eliminated, neutralized, or blocked, or until they decay naturally. In general, there is a 1- to 2-hour window of time during which absorption of these particles occurs. Therefore, it is crucial that any interventions be performed during this period and as soon as possible.
At times, it may be difficult to determine the presence of an internal contaminant, especially if an external contaminant still clouds the picture. Clues may include the evidence of contamination around the mouth and nose. In addition, special treatment considerations will be determined by the type of radioactive material involved. Therefore, it is extremely important to identify the offending agent as early as possible, so that specific therapies may be started. These therapies include chelation and ion binding.
Diethylenetriaminepentaacetic acid (DTPA) administered as calcium-DTPA (Ca-DTPA) or zinc-DTPA (Zn-DTPA) are injectable chelators used for decorporation of plutonium and other transuranics (e.g., americium and curium) from the body. The United States Food and Drug Administration (FDA) approved both of these agents in 2004 for this indication.20 Ca-DTPA should be given as the first dose as Ca-DTPA is more effective than Zn-DTPA during the first 24 hours after internal contamination. However, after the initial 24 hours, Ca-DTPA has no significant advantage over Zn-DTPA. If ongoing treatment is needed or if treatment is initiated over 24 hours after internal contamination, then Zn-DTPA is preferred as Ca-DTPA causes more loss of essential metals.21
In 2003, the FDA approved the use of Prussian blue (ferric ferrohexacyanate) for the treatment of known or suspected internal contamination with radioactive cesium and thallium. Thallium and cesium undergo enterohepatic circulation. Prussian blue works by trapping thallium and cesium in the gastrointestinal tract, so that they cannot be reabsorbed. Instead they can be passed out of the body in the stool. By enhancing the elimination of these elements from the body, Prussian blue may reduce the risk of death and major illness from internal radioactive cesium or thallium contamination.22 Inquiries for acquisition of any of DTPA agents or Prussian blue can be made to REAC/TS at 865–576–1005.
Other specific measures include the use of saturation and blocking. A blocking agent reduces radioactive uptake by saturating the tissues with a nonradioactive element. Potassium iodide (KI) is a blocking agent that reduces the uptake of radioactive iodine (131I) by the thyroid gland. The administration of potassium iodide is most effective at blocking the uptake of radioactive iodine when given soon after exposure. One model demonstrates that potassium iodide would yield protective effects as high as 80% if administered 2 hours after exposure in individuals with an iodine-sufficient diets. However, this benefit would be reduced to 40% when potassium iodide was administered 8 hours after exposure.23 An estimated thyroid exposure of 5 rad or more warrants the initiation of this treatment.24 If the diagnosis has not yet been confirmed, there is little harm in administering a first dose of potassium iodine. Indeed, urgent consideration should be given to the administration of this agent to the pediatric population since they are especially vulnerable to radiation-induced thyroid disease.2 The dose of KI is age dependent (Table 142-6).
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TABLE 142-6 |
Potassium Iodide Dosing |
A comprehensive list of radioactive agents and their respective treatments is beyond the scope of this text. Detailed and current information can be obtained from REAC/TS or through many poison control centers.
Ingestion Initial stabilization and decontamination of radiation ingestions are the same as those for “routine” ingestions. In addition to supportive care measures, the goal is to prevent absorption and enhance elimination. Gastric decontamination procedures such as gastric emptying methods and activated charcoal are used in the usual manner. All bodily excretions (lavage fluid, emesis, urine, and feces) should be saved and labeled for radioactive evaluation and proper disposal. If ingestion is suspected, urine and feces should continue to be tested for 4 days.
Inhalation Acute inhalation of radionucleotides is much less common than chronic low-level exposure. An acute inhalation contamination can occur in the event of a radioactive accident in conjunction with a fire or explosion. Radioactive iodine, for example, is highly volatile and likely to be inhaled. Any patient exposed to external contamination that has undergone endotracheal intubation should be treated as internal contamination.25
When an inhalation contamination is suspected, a moistened cotton-tipped applicator can be used to swab the nasal passages and check for radioactivity. Bronchopulmonary lavage is performed for removal of particulate matter. Specific-blocking agents and chelating agents should be administered in this setting.
Open Wounds Wounds that undergo successful decontamination can be surgically closed. Wounds that remain contaminated despite aggressive irrigation are left open for 24 hours. Debridement of these wounds may become necessary for further decontamination. Contaminated surgical instruments must be replaced to prevent further wound contamination.
Amputation of contaminated extremities is rarely indicated. Two situations may warrant this aggressive management. In the first, the amount of persistent contamination is so high that severe radiation-induced necrosis is anticipated. In the second, the degree of traumatic injury is so severe that functional recovery is doubtful.
EXPOSURE
Aggressive supportive care is the mainstay of treatment for these patients—including fluid resuscitation for severe vomiting and diarrhea, standard trauma and burn care. Prophylactic antimicrobial agents, administration of cytokines, and stem cell transplants are other measures that may help decrease morbidity and mortality. The patient will face the greatest risks and management problems several days to several weeks later, at the onset of the manifest illness stage.
In some cases, nothing will alter the patient’s outcome. Victims with a whole-body exposure of >1000 rad will likely die within 2 to 3 weeks.26 For triage purposes, these patients should be classified as expectant or impending. Death ensues from the complications affecting the hematopoietic system as well as the gastrointestinal and central nervous systems. Emergency department management should consist of appropriate sedation, analgesics, and supportive care.
SPECIAL CONSIDERATION
A nuclear explosion presents logistic and patient care issues that may be difficult to manage effectively. To further complicate the situation, routine communications equipment, electronic equipment, and computers may be rendered useless by the electromagnetic pulse generated by the nuclear blast.
Victims of a nuclear explosion will be subject to three types of injury patterns. Mechanical trauma (blunt and penetrating) secondary to the blast effect of the explosion accounts for 50% of the released energy while thermal injury from heat dissipation represents 35% of the energy release. The remaining 15% of the thermonuclear energy release will cause radiation injury, 10% from radioactive fallout, and only 5% as a result of the immediate release of γ-rays and neutrons.
PROGNOSIS
The prognosis for survival and the concern for delayed complications, while important, are not of immediate concern to the emergency physician. The possibilities of leukemia, carcinoma, cataracts, accelerated aging, and secondary congenital defects are all issues that should be addressed at a later time, when personnel are available for counseling. Leukemia and delayed thyroid cancer and breast cancer are of significant concern in children <10 years of age.2,3,27 In utero, exposure to as little as 5 to 10 rad can be associated with mental retardation or a small head circumference.
Based on the presenting symptoms, patients can be classified into three major prognostic classifications: survivor probable, survivor possible, and survivor improbable.
SURVIVOR PROBABLE
This group includes individuals who are asymptomatic or who have minimal complaints that resolve within hours. Initial and subsequent leukocyte counts are not affected and estimated exposure is <200 rad (2 Gy). Following satisfactory decontamination, inpatient care is rarely needed.
SURVIVOR POSSIBLE
This group consists of patients with relatively brief gastrointestinal sequelae, usually lasting <48 hours. After initial presentation and the latent period, patients develop characteristic pancytopenia. Estimated exposure for this group is between 200 and 800 rad (2–8 Gy). An exposure of 400 rad represents the median lethal dose. Survival in this group is influenced by the aggressiveness of supportive therapy and hematologic intervention, antecedent health of the victim, and the response to bone-marrow transplantation (when indicated).
SURVIVOR IMPROBABLE
In these patients, the estimated whole-body exposure exceeds 800 rad (8 Gy). The prognosis is dismal despite aggressive supportive therapy and even the implementation of bone-marrow transplantation. If severe nausea, vomiting, and diarrhea begin within 1 hour of exposure and CNS symptoms appear early, a relatively early death can be expected.
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