You are in: eMedicine Specialties > Emergency Medicine > WARFARE - CHEMICAL, BIOLOGICAL, RADIOLOGICAL, NUCLEAR AND EXPLOSIVES CBRNE - Radiation EmergenciesArticle Last Updated: Nov 9, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Jeanne S Pae, MD, Staff Physician, Department of Emergency Medicine, New York University, Bellevue Hospital Center Jeanne S Pae is a member of the following medical societies: American College of Emergency Physicians and Emergency Medicine Residents Association Coauthor(s): Curt E Dill, MD, Assistant Professor, Department of Emergency Medicine, New York University School of Medicine; Medical Director, Emergency Care Institute; Consulting Staff, VA Medical Center, Tisch Hospital, Brookdale Hospital Center, Bellevue Hospital Center Editors: Jerry L Mothershead, MD, Medical Readiness Consultant, Medical Readiness and Response Group, Battelle Memorial Institute; Advisor, Technical Advisory Committee, Emergency Management Strategic Healthcare Group, Veteran's Health Administration; Adjunct Associate Professor, Department of Military and Emergency Medicine, Uniformed Services University of the Health Sciences; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Rick Kulkarni, MD, Medical Director, Assistant Professor of Surgery, Section of Emergency Medicine, Yale-New Haven Hospital; John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center; Robert G Darling, MD, FACEP, Clinical Assistant Professor of Military and Emergency Medicine, Uniformed Services University of the Health Sciences, F Edward Hebert School of Medicine; Director, Center for Disaster and Humanitarian Assistance Medicine Author and Editor Disclosure Synonyms and related keywords: radiation emergencies, radiation exposure, ionizing radiation, nuclear energy, radioactive contamination, acute radiation syndrome, ARS, radiation burns, nuclear radiation exposure, nuclear weapons, nuclear bombs, radiation dispersal device, RDD, radiation emergency, radiation toxicity, health effects of radiation exposure INTRODUCTIONSection 2 of 10
  All organisms are continuously exposed to radiation from either natural or synthetic sources. In the United States, the average dose of radiation an individual receives per year is estimated to be 3.6 milliSieverts (mSv), 80% of which is from natural sources and 20% of which is from man-made sources. The full effects of low-dose natural radiation are not known, but high doses have been shown to be carcinogenic. At very high-dose exposures over a short period of time, immediate and lethal health effects can occur. Generally, the toxicity caused by radiation is directly related to the quantity of energy deposited into the living organism and the subsequent disruption of metabolic and reproductive pathways. Low-level exposure from accidental contact with radioactive isotopes in laboratory research may lead to relatively minor toxicity. Alternatively, acute sickness and even death may occur after the inappropriate handling of high-level radioactive material such as cobalt-60 from radiographic or radiotherapy machinery. In a terrorism context, a radiation dispersal device (RDD), "dirty bomb," could result in conventional blast and thermal injuries. If these devices are laced with significant amounts of radioactive material, the additional risk of radiation exposure would exist for both bomb victims and rescue workers. Detonation of nuclear weapons or improvised nuclear devices would lead to catastrophic blast and thermal injuries in addition to far-reaching lethal radiation consequences. Over the past 50 years, most radiation incidents have had nonlethal consequences. According to the Radiation Accident Registry maintained by the Radiation Emergency Assistance Center/Training Site (REAC/TS) at the Oak Ridge Institute, from 1944-1999, 403 radiation accidents occurred worldwide, with 243 of those occurring in the United States. Of the total, 303 involved radiation devices from sealed sources or x-ray machinery, 81 involved radioisotopes, and 19 involved nuclear reactors. These incidents have led to 120 total deaths: 30 in the United States, 2 in Great Britain, and 32 in the former USSR. TERMINOLOGYSection 3 of 10
Radioactivity Radioactive decay is the process in which unstable atomic nuclei assume a more stable configuration by emitting particles with kinetic energy (alpha or beta particles) or electromagnetic waves (gamma rays). If a person is exposed to these high-energy particles or electromagnetic waves, energy is deposited into the tissues and can cause injury. Ionizing versus nonionizing radiation Radiation can be broken down into 2 categories: ionizing radiation and nonionizing radiation. The term ionizing radiation refers to either high-energy particles or electromagnetic waves that have the ability to deposit enough energy to break chemical bonds and produce an ion pair. Ionization occurs when the process of energy transfer liberates an orbital electron from an atom or molecule producing this ion pair. If living cells receive this energy, cellular function becomes compromised by DNA damage and mutation. Nonionizing radiation refers to radiation that lacks the energy to liberate orbital electrons. All radiation from the electromagnetic spectrum except x-rays and gamma rays are included in this category. Examples of nonionizing radiation include microwaves, visible light, and infrared light. Because nonionizing radiation is lower energy radiation, injury is usually related to local heat production and is generally less severe. Ionizing radiation is consequently the focus of radiation-induced injury. Ionizing radiation: electromagnetic radiation Energy can travel through space in the form of electromagnetic radiation. Electromagnetic radiation is composed of massless waves of oscillating electric and magnetic fields. In a vacuum, these waves move at a constant speed, the speed of light (3 X 108 m/s). All electromagnetic waves propagate with characteristic wavelength and frequency, with the wave's energy being directly proportional to frequency and inversely proportional to wavelength. Within the electromagnetic spectrum, only x-rays and gamma rays have enough energy to produce ion pairs. The remaining waves within the spectrum, such as microwaves and radiowaves, are nonionizing. Ionizing radiation: particulate radiation Ionizing radiation can also be in the form of particulate radiation, which includes small charged or neutral particles traveling with high energy. These particles may be alpha particles, electrons (beta particles), neutrons, or protons. Alpha particles are charged particles made up of 2 protons and 2 neutrons with zero electrons—essentially the nucleus of a helium atom. These particles are emitted from radioactive nuclei of uranium and radium. Because of their large mass and positive charge, alpha particles are highly effective in transferring energy to tissue but are also easily blocked by a piece of paper or clothing. These particles are only a concern when alpha-emitting isotopes are ingested or inhaled. A well-recognized source of alpha radiation involves the decay of radium into radon gas. Radium is an alkaline earth metal and a decay product of uranium and is found in uranium-bearing rocks or ores. Radium decays into radon gas, which can accumulate in poorly ventilated areas such as basements. Inhalation of radon on dust particles can lead to substantial doses of alpha radiation to the bronchi or lungs. The US Environmental Protection Agency attributes 10,000-20,000 cases of lung cancer per year to radon exposure. Beta particles are another type of particulate radiation. These particles are high-energy electrons emitted from decaying isotopes such as strontium-90. These high-energy electrons are also easily produced in linear accelerators and are commonly used to generate x-rays and in cancer radiotherapy. As in alpha radiation, the main hazard with beta particles lies with internal exposures. With significant skin exposure, however, beta particles have sufficient energy to cause cutaneous burns, "beta burns." A neutron is an electrically neutral particle found within the nucleus of an atom. Neutrons are slightly greater in mass than protons. High-energy neutrons rarely occur naturally but can be produced in a particle accelerator or in nuclear reactor as part of the fission process. Neutron exposure is most consequential in a nuclear reactor criticality accident or during nuclear weapons detonation. A proton is a positively charged particle that is more than 1800 times the size of an electron. Protons make up a major component of cosmic radiation originating from the sun. All but a small amount of the sun's proton radiation is deflected by the earth's magnetic field. Irradiation, contamination, and incorporation Irradiation occurs when a person is exposed to ionizing radiation. For example, patients who receive x-rays or CT scans become irradiated. Once the radiographic machinery is turned off, radiation is no longer produced. Because these individuals are only in the path of radiation energy as opposed to carrying a radioactive source on their bodies, they pose no radiation exposure risk to others. Contamination refers to the presence of radioactive material where it is undesirable. If a person's skin or clothing is contaminated with radioactive material, irradiation continues to occur until the radioactive material is removed. Under some conditions of high contamination, these individuals may pose an exposure threat to others. Unless the contaminated patients are severely ill from the exposure, it is unlikely that they pose a significant risk to other patients or healthcare workers. Incorporation of radioactive material occurs with cellular uptake of radioactive material via inhalation, via ingestion, or through open wounds. These radioactive atoms participate in the same physiologic pathways as nonradioactive atoms. Because removing radioactive material from the body is very difficult once incorporation occurs, the best treatment philosophy is to minimize exposure and decontaminate to prevent incorporation. As with contaminated individuals, only those who are severely ill truly pose a risk to others. BIOLOGIC EFFECTS OF IONIZING RADIATIONSection 4 of 10
Ionizing radiation causes injury to cells via breakage of DNA strands (direct action) or from the production of hydroxyl or peroxide radicals that cause oxidative damage to DNA (indirect action). Both mechanisms ultimately lead to DNA strand breaks. Single-strand breaks can be mended rather easily utilizing the intact template on the remaining strand. However, double-strand DNA breaks have no intact template and repair is much more difficult. If the cell is unable to repair the damaged chromosome, it loses reproductive integrity and ultimately undergoes mitotic death. Apoptosis, or programmed cell death, can also occur after exposure to ionizing radiation. Some human cells are particularly sensitive to low levels of radiation. Once exposed to radiation, these cells exhibit activation of a signaling cascade that leads to DNA fragmentation and rapid cell death. Human cells that undergo radiation-induced apoptosis include lymphocytes and acinar cells of the salivary glands. Early versus late radiation effects Radiation toxicity can be divided into early and late effects. Early effects of radiation are seen after large doses of radiation are delivered over short periods of time. Early toxicity is generally seen in rapidly dividing, self-renewal organs including skin, bone marrow, and gut epithelium. Early radiation effects are responsible for clinical syndromes that may be encountered in the emergency department following a massive exposure. Late toxicities are generally seen in organs with slowly dividing or quiescent, terminally differentiated cells. Organs in which late toxicities are common include the central nervous system, kidneys, and liver. Many late radiation effects are attributable to a combination of parenchymal cell death and microvascular disease. The most well-known delayed complication of radiation exposure is malignancy. Exposures to the Chernobyl accident and atomic bomb testing in the Marshall Islands led to high incidences of thyroid malignancies. Atomic bomb survivors have been shown to have an increased risk of leukemia, and young women with Hodgkin disease treated with radiation therapy have been shown to have an increased risk for breast cancer. RADIATION DOSESection 5 of 10
The absorbed dose of radiation is the amount of energy absorbed by biologic tissue. Radiation dose is measured in Gray (Gy) or radiation absorbed dose (rad). Gray is the SI unit for dose and is expressed as J/kg. One gray is equal to 100 rad. Since the biologic effects of different types of radiation (eg, gamma vs alpha vs neutron) vary significantly, expressing radiation exposure in terms of equivalent dose is sometimes useful. By assigning a weighting factor to each type of radiation (gamma = 1, alpha = 20), the equivalent dose can be calculated by multiplying the absorbed dose (Gy) by the radiation weighting factor. Equivalent dose is then expressed in sieverts (Sv). CLINICALSection 6 of 10
Localized cutaneous injury Localized exposure to high doses of radiation may cause cutaneous injury similar to burns. Blistering, erythema, desquamation, and ulceration often present about 12-20 days after irradiation with the onset and severity related to the magnitude of exposure. A local exposure of 3 Gy leads to epilation within 1-2 weeks. A local exposure of 6 Gy may cause immediate signs of burn. Greater exposures of 10-15 Gy lead to dry desquamation, and exposures of 20-50 Gy lead to wet desquamation (partial-thickness burn) within 2-3 weeks. For doses greater than 50 Gy, a cutaneous syndrome of necrosis and ulceration may occur from damage to endothelial cells and small blood vessels. Vascular complications may present months to years after exposure. Acute radiation syndrome The acute radiation syndrome (ARS) occurs after whole-body exposure to a large dose of ionizing radiation. This syndrome includes a number of characteristic signs and symptoms whose severity depends on magnitude of dose and duration of exposure. ARS, by definition, does not occur at doses less than 1 Gy and is uniformly fatal at doses greater than 10 Gy. The estimated LD50/60 (the dose at which 50% of those exposed die within 60 days) is 3.5 Gy for humans without medical treatment and roughly 7.0 Gy with treatment. Frequently, the exact details of an accidental exposure are not known, leaving uncertainty in dose assessments. Clinical presentation, symptomatology, and laboratory measures, especially in the early period, can be used to indirectly determine dosage of exposure and prognosis. Stages of ARS ARS has been described according to progression of illness through 4 stages: (1) prodrome, (2) clinical latency, (3) manifest illness, and (4) recovery or death. The prodromal symptoms occur shortly after irradiation, with the dose of exposure determining severity, duration, and onset. Common prodromal symptoms include nausea, vomiting, anorexia, fatigue, diarrhea, abdominal cramping, and dehydration. At doses of greater than 10 Gy, those exposed show symptoms within 5-15 minutes; at lower doses such as 2-3 Gy, symptoms can take up to 12 hours to present. Immediate diarrhea, hypotension, and fever indicate a supralethal exposure. Severe and early onset of prodromal symptoms indicates higher dosage of exposure and a poor prognosis. Progression through the other phases depends on dosage of exposure. Classic ARS syndromes ARS is further described by its 3 classic subsyndromes: the hematopoietic syndrome, the gastrointestinal syndrome, and the cerebrovascular syndrome. The hematopoietic syndrome typically occurs after exposures of 2-5 Gy. At these doses, lymphocytes die from radiation-induced apoptosis, and precursor cells in the bone marrow are destroyed preventing new production of leukocytes and platelets. During the period of a few weeks (clinical latency), circulating cells die off with no replacements; it is at this nadir that the full syndrome becomes clinically apparent with development of infections and possible hemorrhage. Anemia from red cell depression usually does not occur alone in the absence of hemorrhage. Early supportive care, treatment and prevention of infections, and the consideration of cytokine therapy are all important aspects of care for this subsyndrome. However, even if the hematopoietic syndrome is treated, death commonly still occurs from multiorgan failure. The gastrointestinal syndrome usually occurs after exposures of more than 5-12 Gy. Irradiation leads to death of intestinal mucosal stem cells in the crypts. After loss of mucosal cells at the villi through normal functioning, the stem cells are unable to produce new cells, leading to denudation of the GI tract. As the normal GI boundary is compromised, bacterial growth proliferates increasing the risk of sepsis. Common symptoms include anorexia, nausea, vomiting, prolonged bloody diarrhea, abdominal cramps, dehydration, and weight loss. Often the prodrome onset is rapid, followed by a latent period of roughly 1 week then return of symptoms. The mainstays of treatment are fluid and electrolyte balance and infection prevention, but death often follows in 3-10 days. The cerebrovascular syndrome occurs after exposures of very high doses (>30 Gy) and is uniformly fatal. At doses of greater than 100 Gy, death occurs within hours. Although the exact mechanism of death is not fully understood, vascular damage is thought to lead to significant cerebral edema, producing neurologic and cardiovascular collapse. Immediate symptoms include nausea, vomiting, hypotension, ataxia, and convulsions, and death follows in a few days. Time to emesis Past studies have suggested time to emesis (TE) as one clinical parameter that can be used to indirectly determine dosage exposure. TE postradiation exposure seems to decrease as dosage increases. For TE less than 1 hour, the whole-body dose is estimated to be greater than 4 Gy. For TE between 1 and 2 hours, whole-body dose is estimated to be greater than 3 Gy, and for TE greater than 4 hours, whole-body dose is estimated to be around 1 Gy. WORKUPSection 7 of 10
The most useful laboratory test in the setting of acute radiation exposure is the serial complete blood count with differential obtained every 6-12 hours. Lymphocyte count serves as an indicator for prognosis and as an estimate for the dose of radiation received. Patients with a minimal lymphocyte count (MLC) of 1000-1499/mm3 have an approximate absorbed dose of 0.5-1.9 Gy. Although these patients may have clinically significant effects, their prognosis is good because the absorbed dose is usually nonlethal. Patients with MLC of 500-999/mm3 have an approximate absorbed dose of 2.0-3.9 Gy with severe injuries and fair prognosis. An MLC of 100-499/mm3 coincides with an approximate absorbed dose of 4.0-7.9 Gy predicting severe injury and a poor prognosis, and those with MLC less than 100/mm3 have an estimated absorbed dose of greater than 8 Gy and have a high incidence of death despite bone marrow stimulation. Survival has not been documented for those exposed to greater than 10 Gy. Blood can also be drawn for cytogenetic evaluation. If dicentrics (chromosomes with 2 centromeres) are found, they can be used to indicate extent of radiation exposure. Cytogenetic studies are time-consuming processes that are currently not being used for mass screening strategies. Realistically, these studies may be more useful from an inpatient standpoint. TREATMENTSection 8 of 10
Prehospital care In the instance of radiation accidents, prehospital personnel should wear appropriate protective gear prior to arrival at the scene and follow the guidance of the radiation safety officer or operations commander. If possible, field personnel should elicit type of radioactive material involved and extent of exposure. If a high radiation field is discovered, areas of operation should be determined. Clinical operations may be required in higher exposure areas, but exposure limits should be strictly regulated by supervisors. Decontamination at or near the site of exposure is important, as simple clothing removal is believed to eliminate up to 90% of contamination. Unfortunately, proper decontamination is difficult to perform in the field, and personnel at receiving hospitals may find this step bypassed. If prehospital decontamination is possible, contaminated clothing and water should be collected as biohazardous material. If other injuries have occurred, BLS/ATLS protocols should be initiated and unstable patients should be rapidly transported to appropriately equipped hospitals. Emergency department care In general, treatment of conventional injuries and illness takes precedence over radiation concerns. The quantity of radioactive material that a contaminated individual carries on his or her body is unlikely to present a significant radiation risk to hospital workers. No cases are known of healthcare personnel becoming acutely ill caring for contaminated or irradiated victims of radiation accidents. Critically ill and injured patients should be moved into critical care areas of the hospital and should be decontaminated during resuscitation. In a mass casualty event, most patients arrive without prehospital decontamination necessitating appropriate screening strategies in accordance with the Hospitals Incident Command Structure (HICS). Specific treatments Patients with localized irradiation that present with cutaneous injury should be treated in the same manner as those with thermal burns. Pain control and infection prophylaxis are the mainstays of treatment. In the cases of severe burns, vasodilator therapy, grafts, or amputations may be necessary. After whole-body radiation exposure, appropriate decontamination should occur. Patients who present with prodromal symptoms should be treated supportively with intravenous fluids, analgesics, and antinausea medication. For exposures of around 5 Gy, most experts recommend supportive care, antibiotics for infection, consideration of cytokine therapy, and transfusions as needed. Blood products should be leukocyte-poor and irradiated to 25 Gy, but transfusions should not be given prophylactically because they may blunt the stimuli for cell regeneration. For exposures greater than 5 Gy, death from gastrointestinal syndrome is highly likely. Along with antibiotics and platelet transfusions as needed, physical trauma and avoidance of infection (isolation) should be stressed. In cases of internal ingestion or contamination of unknown radioactive materials, some measures (eg, lavage, charcoal) to decrease absorption may be effective and can be used if not contraindicated. Similarly, specific therapies exist to remove some internally deposited radionuclide albeit with limited efficacy. These treatments are often in limited supply, complex in action, and associated with significant risks. Thoughtful and critical analysis should be take place prior to administration. Internal contamination by radioactive iodine can be treated with saturated solution of potassium iodide (SSKI), a blocking agent that reduces uptake of radionuclide in the thyroid. SSKI is most effective when taken within a few hours of exposure. In reactor accidents involving radioactive iodine, massive quantities are released into the environment. Both exposed victims and rescue personnel should take SSKI to reduce thyroid uptake of radioiodine to reduce risk of future malignancies. Specific dosages for SSKI administration can be viewed at Guidance for Industry – KI in Radiation Emergencies—Questions and Answers. Chelating agents, such as penicillamine, bind specific radioactive metals causing decreased tissue uptake and increased excretion. Exposure to isotopes of cesium can be treated with ferric hexacyanoferrate (Prussian blue) to decrease gastrointestinal absorption. Agents such as Ca-DTPA and Zn-DTPA can be administered after internal contamination with substances such as americium or plutonium. Administration of specific agents should be done in consultation with professionals familiar with these agents. Further inpatient care During periods of infection, antibiotics should be tailored toward the source of infection. If absolute neutrophil count (ANC) is less than 500 cells/mm3, most experts recommend prophylactic antibiotics including a fluoroquinolone, an antiviral agent (acyclovir in those with a history of herpes simplex virus), and an antifungal agent. Once fever and infection occur, broader antibiotics with additional antipseudomonal coverage should be initiated. The use of bone marrow transplants remains controversial. Of the 13 Chernobyl victims who received bone marrow transplants, only 2 survived, one of whom had autologous marrow repopulation; thus only one survivor was thought to be saved by a bone marrow transplant. The dose window appropriate for bone marrow transplantation is thought to be between 8 and 10 Gy, as those who receive less than 8 Gy may survive with conservative treatment, antibiotics, and transfusions, whereas those who receive greater than 10 Gy uniformly die. Administration of hematopoietic growth factors to stimulate bone marrow post irradiation also remains investigational. Past studies have shown a benefit in animal models increasing neutrophil counts in primates irradiated with Cobalt-60. In a 2004 paper, Waselenko et al proposed recommendations for giving colony-stimulating factors (CSF) to victims of radiation exposure. His team recommended giving granulocyte-macrophage colony-stimulating factor (GM-CSF) to those who receive more than 3 Gy of radiation and in those with multiple injuries who are exposed to more than 2 Gy. Recommended doses include initiating therapy with filgrastim at 5 µm/kg/day or sargramostim at 250 µm/m2/day subcutaneously immediately after exposure and continuing until absolute neutrophil count increases to greater than 1,000 cells/mm3. Alternative treatment with subcutaneous pegfilgrastim weekly to those greater than 45 kg has also been suggested. MISCELLANEOUSSection 9 of 10
Useful Web sites Armed Forces Radiobiology Research Institute Radiation Emergency Assistance Center/Training Site Centers for Disease Control and Prevention, Emergency Preparedness and Response, Radiation Emergencies Guidance for Industry – KI in Radiation Emergencies—Questions and Answers REFERENCESSection 10 of 10
CBRNE - Radiation Emergencies excerpt Article Last Updated: Nov 9, 2006 |
