Online Articles and Submission
                    

Annals of Disaster Medicine

ISSN:1684-193X

Updated Oct 30, 2003

Contents:
Volume 2, Supplement 1; October, 2003
Acute Radiation Syndrome
Li-Wei Lin, MD, Tzong-Luen Wang, MD, PhD

 

From the Department of Emergency Medicine (Lin LW, Wang TL), Shin-Kong Wu Ho-Su Memorial Hospital.

Correspondence to Dr. Tzong-Luen Wang, Department of Emergency Medicine, Shin-Kong Wu Ho-Su Memorial Hospital, 95 Wen Chang Road, Taipei, Taiwan. E-mail M002183@ms.skh.org.tw

 

Abstract

   
Acute radiation syndrome is an acute illness caused by irradiation of whole body or a significant portion of it from electromagnetic waves or accelerated atom particles. It is a sequence of phased syndrome: prodromal phase, latent period, clinical illness and one of recovery or death. The extent and duration of symptoms depend on individual radiation sensitivity, type of radiation, and radiation dose absorbed. Increasing radiation dose will heighten the severity of symptoms and shorten the duration of each phase. The three clinical forms of acute radiation syndrome depending on radiation dose are hematopoietic, gastrointestinal and neurovascular. Hematopoietic syndrome produces lymphopenia first then pancytopenia and increases the risk of infection and bleeding. Gastrointestinal syndrome is characterized by loss of the villus structure of intestine and then development of severe GI bleeding, diarrhea and abdominal pain along with hematopoietic syndrome. Neurovascular syndrome happened minutes after exposure with symptoms of vomiting, hypotension, ataxia, confusion, and seizures. Fatality is near 100%. Emergency physicians must recognize the manifestations of radiation syndrome, so we can provide optimal management for radiation victims.
Key words--- Radiation Syndrome; Radiation Accident; Disaster Medicine

 

Introduction

 
   
Radiation incident is rare condition but worldwide, the number of radiation incidents has reached 403 since 1944.1 They influenced with 133,617 victims, of which 2965 had significant exposures and 120 persons died. Most acute radiation injury is related to nuclear weapons, industrial accidents, nuclear power accidents and radiation therapy. After terrorist attacked on the World Trade Centers on September 11, 2001, the United States and all developed nation had increasing concern about the possibility of nuclear terrorism. The terrorist attack may include dispersal of radioactive substances with or without the use of conventional explosives, attacks on nuclear reactors and detonation of nuclear weapons.2 In the United State nuclear attacks are thought easier to manage than bio-chemical terrorism because more then 10,000 persons deal with radiation daily at hospitals, universities, military units, national laboratories and government agencies. Geiger counters or dose-rate meter are available in more than 3,000 hospitals. Emergency personnel can carried these equipments to detect radioactive contamination and use a simple blood test, absolute lymphocyte counts and clinical manifestation of acute radiations symptoms to assess the severity of radiation injuries. In Taiwan we lack of the experience of management of radiation crisis so we required a thorough understanding of radiation syndromes for effective management of radiation casualties.
 
History
 
Most acute radiation injury is related to accidents or radiation therapy. Accidents are sporadic and usually effect small numbers of victims. The first large-scale exposure to radiation has been caused by the detonation of atomic bombs over Japan in World War II. One-hundred and twenty thousands individuals developed acute radiation syndrome. In the Marshall Islands 7,266 natives were exposed to radiation due to errors in judging winds after a nuclear test in the South Pacific in 1954.3 A radiation incident involving a medical Cs-137 source in Brazil resulted in 200 contaminated persons and 4 deaths.4 A nuclear accident at the Chernobyl nuclear power station in Russia in 1986 had exposed more than 116,500 persons and resulted in 29 deaths from acute radiation syndrome.5
 
 
Epidemiology  
   

Radiation is energy traveling through the space. Radiation includes electromagnetic emissions and particles.6 Ionizing radiation means electromagnetic (X ray and gamma) or particulate (alpha, beta and neutron) radiation capable of producing ions or charged particles. Ionizing radiation comes from unstable atoms that had radioactivity to emit radiation spontaneously.
Gamma and X rays are electromagnetic radiation like light, radio waves and ultraviolet light but they have short-wave, high-frequency and more energy. Gamma and X rays travel many meters in air and several centimeters in human tissue. They penetrate most materials and is called penetrating radiation. Only dense materials like lead shied prevent penetrating radiation. A person exposed to penetrating radiation is not radioactive.
Alpha radiation has 4 neutron masses and +2 charges. It travels only a few centimeters in air and cannot penetrate skin. It can be hazard from inhaled, swallowed, or absorbed through open wounds with alpha-emitting materials. Paper and keratin layer of skin provide protection against for most alpha radiation.
Beta radiation is thru electrons and travels meters in air and up to 8 millimeters into skin. It may be harmful if beta-emitting materials deposited on skin or internally. Beta radiation can be prevented by clothing and turnout gear.
Neutrons possess a large range of energy and variable penetrating ability. The major source of neutrons comes from critical accidents around nuclear power production facilities or nuclear weapons. It had a unique property that a stable atom may absorb a neutron and then become an unstable atom. Metallic object worn or implanted in the affected person and sodium in human body will become radioactive.
Ionizing radiation produces free radicals from water and then disrupts chemical bonds. This causes damage of cellular biochemical systems and DNA. Cellular replication and protein synthesis are further disrupted. If higher radiation dose absorbed damage will overcome the ability of repair. In general rapid replicating cells are vulnerable to radiation, e.g. blood, gut, epithelium, and reproductive cells. Clinically young patients, men and debilitated patients are more susceptible from radiation.

 
 
Radiation Measuring  
   

Variable methods were developed for measuring radiation. The dose and amount of radiation absorbed by the exposure person determinate the toxicity   of radiation injury. The units of radiation measure are listed in Table.1 Common radiation-monitoring equipments include dosimeters and survey meters.
Dosimeters were worn on the upper torso to record the cumulative dose of beta, X and gamma rays. Two types are thermoluminescent dosimeter or film badge and pocket dosimeter. But these devices need processing. Some self-reading pocket dosimeters may be read immediately. Measurement is typically recorded in milliroentgen (mR).

Geiger counter and ionization chamber are types of survey meters for recording exposure rate of radiation. Geiger counter is used for detecting low exposure of X, gamma and beta radiation. With special instrument GM counter can detect alpha radiation. Ionization chamber is for high exposure of X and gamma rays. Estimates are typically recorded in cpm and mR/h. 2500 cpm is equal to 1 mR/h.

 
 
Table .Units of Radiation Measur
 
 
Clinical acute radiation syndrome  
 

Acute radiation syndrome has somewhat predictable clinical courses.7 During prodromal phase nausea, vomiting and fatigue happen. According to absorbed dose its onset begins from 3-6 hours to minutes and last from 24 to 48 hours. Latent phase follows prodromal phase and last up to 2 weeks. In the period bone marrow suppression and gastrointestinal system destruction occur insidiously but the victim is asymptomatic. Clinical illness develops after affected systems loss its function. Depending on absorbed radiation dose it divides to hematopoietic, gastrointestinal and neurovascular syndrome. Death or recovery follows the critical period.
Whole body irradiation dose at < 2 Gy is considered subclinically.1,2,6-8 No symptoms develop when exposure to < 0.75-1 Gy. At 1- 2 Gy nausea and vomiting occur 3-6 hours later after events and last shorter than 24 hours. Under this exposure radiation victims have no disease.

 
 
Hematopoietic Syndrome  
When exposure dose is greater than 2 Gy, acute nausea and vomiting (50-100%) happen within 3 hours and last 24-48 hours depending on lower or higher dose. Latent phase follow from 2 days to 2 weeks. Acute leukocytosis present after irradiation and then lymphocyte falls. Thrombocytopoenia, neutropenia and anemia follow in sequence. The maximum effect on bone marrow suppression occurs at 3 weeks after radiation exposure. Infection and bleeding developed due to neutropenia and thrombocytopoenia. During this clinical phase infection and sepsis, especially with Gram-negative bacteria are leading causes of mortality. Death rate is 0-90% depending on dose received and treatment.
 
   
Gastrointestinal Syndrome  
Over 10 Gy exposure gastrointestinal syndrome occur but also may occur at lower dose such 5 Gy. LD 50 for human without treatment is about 325 rads. Nausea and vomiting happened within 1 hour after exposure. Nausea, vomiting and diarrhea are more profuse than hematopoietic syndrome. Villus structures are destroyed and massive amount of plasma are shift to the intestine. Severe gastrointestinal symptoms recur within 1-3 days with diarrhea, gastrointestinal bleeding and abdominal cramping. These induce fluid loss, electrolyte imbalance, dehydration, septicemia and shock. Hematopoietic syndrome follows soon later. Mortality is usually caused by bleeding and Gram-negative sepsis. Survivals are usually complicated late by bone marrow suppression. With treatment death rate is 90-100%.
 
   
Neurovascular Syndrome  
Neurovascular syndrome is the most dangerous condition of radiation injury associated with exposure to radiation dose greater to 30 Gy. Nausea, vomiting, and prostration occur within minutes. Tremor, ataxia, confusion, convulsion, hypotension and hyperpyrexia develop within hours. Patients who receive more than 50 Gy usually die within 24 to 48 hours. Fatality is near 100%.
 
 
Diagnosis  
   

Acute radiation syndrome is clinically suspected by history of exposure, clinical symptoms and laboratory tests.
(1)    
Patients develop a predicable pattern of acute radiation syndrome after a history of radiation exposure
(2)    
Specific symptoms with a 2-3 week prior history of unexplained nausea and vomiting, are

  • Thermal burn lesion without heat or chemical exposure
  • A tendency to bleed (epistaxis, gingival bleeding, petechiae)
  • Infection with bone marrow suppression (neutropenia, lymphopenia and thrombocytopoenia)
  • Epilation                    

(3)     Obtain complete blood count with differential immediately post event. Repeat every 6 hours for 48 hours. Absolute lymphocyte count at 48 hours predicts the exposure radiation dose.2

  • Over 1500= trivial or no exposure, 0-0.4 Gy, Excellent prognosis
  • Over 1000= moderate injury, 0.5-1.9 Gy, survival without treatment
  • 500-1000= severe injury, 2.0-3.9 Gy, survival with treatment
  • 100-500= very severe injury, 4.0-7.9 Gy, death without bone marrow transplant
  • Under 100= lethal injury, >8.0 Gy, certain death

(4)     Swabs from body orifices and wounds if external contamination is suspected. Collect 24 hours urine and stool if internal contamination is possible.

 
Treatment  
Medical management for radiation emergency includes triage, emergency care, and definitive care. During triage we focus on immediately life-threatening problems and priority. Emergency care includes decontamination, therapy and diagnosis of radiation and combined injuries. Definitive care provide final disposition and stand care for patients.
 
   
Antiemetics  
Nausea and vomiting was prodromal symptoms after radiation exposure. Use serotonin 5-HT3 receptor blockages, such as garanisetron (Kytril ®) or ondansetron (Zofran ®) will diminish nausea and vomiting.7 But these drugs will not change the clinical course of radiation injury.
 
   
Infection prophylaxis and control  

Sepsis is the primary enemy of radiation victims. Prevention of infection need reverse isolation, avoidance of invasive procedure, such as CVP, NG and Foley, insertion, prophylactic antibiotics and stimulation of hemataopoiesis.
Antibiotics are used only when afebrile patients with absolute neutrophil count<100 cells/£gl or febrile patient with absolute neutrophil <500 cells/£gl. Gram-negative bacterial infections are the most concern such as other patients received chemotherapy with neutropenia and fever.9 Life-threatening gram-positive bacterial infections also would happen. Empire anitibiotics must cover broadly against gram-negative bacteria and be continued least 7 days after defervescenece.
The degree and duration neutropenia increases the risk of infection increases. Use hematopoietic growth factors, such as G-CSF or GM-CSF has important role for severely exposure patients. It shorten the time of neutrophil recovery and decrease the risk of infection. Recommendations for uses of cytokines are Filgrastim (G-CSF) 2.5-5 £gg/kg/QD SC, Pegfilgrastim (pegG-CSF) 6mg QD SC and Sargramostim (GM-CSF) 5-10 £gg /kg/QD SC.7

 
 
Transfusion support  
Transfusion of packed red blood cells and platelets is necessary for symptomatic anemia and severe thrombocytopoenia (platelets< 20,000) or bleeding.10
 
   
Bone marrow transplant  
Bone marrow transplantation or peripheral blood transplantation is indicated when whole body irradiation more than 5 Gy. 11Above this level bone marrow suppression would be irreversible or prolonged. In Chernobyl nuclear reactor accident 13 persons exposure greater than 5 Gy received bone marrow transplantation and only 2 persons survived.
 
   
Summary  
Acute radiation syndrome has a predicable pattern of disease progression. Absorbed dose can be simple calculated by the fall of absolute lymphocyte count and dosimeters. Understand the absorbed radiation dose physicians can estimate outcome and provide proper intervention for radiation causalties. The probability of radiation accidents is rare but real. Emergency health workers must have the knowledge of radiation injury and the skill of decontamination for this challenge.
 
   
References  
   
1. Radiation Emergency Assistance Center/Training Site (REAC/TS). Available at: URL: http://www.orau.gov/reacts
2. Mettler FA, Voelz GL. Current concepts: major radiation exposure-what to expect and how to respond. NEJM 2002;346:1554-61
3. 3. Hamilton TE, van Belle G, LoGerfo JP. Thyroid neoplasia in Marshall islanders exposed to nuclear fallout. JAMA 1987;258:629-36
4. 4. Gal RP. Treatment of radiation victims in Brazil. Science 1988;22:335
5. 5. Linnemann RE. Soviet medical response to the Chernobyl nuclear accident. JAMA 1987;258;637-43
6. Hogan DE, Kellison T. Nuclear terrorism. Am J Med Sci 2002;323:341-49
7. Jarrett D, ed. Medical management of radiation casualties: handbook. AFRRI special publication 03-1. Bethesda, Md.: Armed Forces Radiobiology Research Institute, 2003 (Also available at http://www.afrri.usuhs.mil.)
8. Finch SC. Acute radiation syndrome. JAMA 1987;258:664-7
9. Conklin JJ, Walker RI, Hirsch EF. Current concepts in the management of radiation injuries and associated trauma. Surg Gynecol Obstect 1983;156:809-29
10. Gale P. Immediate medical consequences of nuclear accidents. JAMA 1987; 258:625-8
11. Geiger HJ. The accident at Chernobyl and the medical response. JAMA 1986;256:609-12
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