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Contents:
Volume 2, Supplement 1; October, 2003 |
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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
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Abstract
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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
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Introduction
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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.
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History |
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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
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Epidemiology |
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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.
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Radiation
Measuring |
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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. |
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Table .Units of Radiation Measur |
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Clinical
acute radiation syndrome |
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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. |
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Hematopoietic Syndrome |
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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. |
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Gastrointestinal Syndrome |
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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%. |
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Neurovascular Syndrome |
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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%. |
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Diagnosis |
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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
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Thermal burn lesion without heat or chemical
exposure
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A tendency to bleed (epistaxis, gingival bleeding,
petechiae)
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Infection
with bone marrow suppression (neutropenia, lymphopenia and
thrombocytopoenia)
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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
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Over 1500= trivial or no exposure, 0-0.4 Gy,
Excellent prognosis
- Over 1000= moderate
injury, 0.5-1.9 Gy, survival without treatment
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500-1000= severe injury, 2.0-3.9 Gy, survival with treatment
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100-500= very severe injury, 4.0-7.9 Gy, death
without bone marrow transplant
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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.
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Treatment |
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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. |
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Antiemetics |
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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. |
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Infection prophylaxis and control |
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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 |
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Transfusion support |
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Transfusion of
packed red blood cells and platelets is necessary for symptomatic
anemia and severe thrombocytopoenia (platelets< 20,000) or bleeding.10 |
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Bone marrow transplant |
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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. |
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Summary |
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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. |
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References |
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Radiation Emergency Assistance Center/Training Site
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to expect and how to respond. NEJM 2002;346:1554-61 |
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3. Hamilton TE, van Belle G, LoGerfo JP. Thyroid neoplasia in Marshall
islanders exposed to nuclear fallout. JAMA 1987;258:629-36 |
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4. Gal RP. Treatment of radiation victims in Brazil. Science 1988;22:335 |
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5. Linnemann RE. Soviet medical response to the Chernobyl nuclear
accident. JAMA 1987;258;637-43 |
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Hogan DE, Kellison T. Nuclear terrorism. Am J Med Sci 2002;323:341-49 |
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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.) |
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Finch SC. Acute radiation syndrome. JAMA 1987;258:664-7 |
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Conklin JJ, Walker RI, Hirsch EF. Current concepts in the management
of radiation injuries and associated trauma. Surg Gynecol Obstect
1983;156:809-29 |
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Gale P. Immediate medical consequences of nuclear accidents. JAMA
1987; 258:625-8 |
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Geiger HJ. The accident at Chernobyl and the medical response.
JAMA 1986;256:609-12 |
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