Essential Elements #8-14

Essential Element #8

Hospital Evaluation and Treatment of Radiation Exposure Victims

Question 8-1: What are the signs and symptoms associated with radiation exposure?

Background: Clinical Radiation Exposure Syndromes

Whole-body or nearly whole-body exposure by a significant dose of radiation can result in a systemic acute radiation syndrome. Systemic acute radiation syndromes demonstrate four distinct clinical phases. The onset and duration of each phase is a direct result of the intensity of the exposure. In addition to clinical manifestations, the intensity of a radiation exposure can be estimated from the degree of bone marrow depression.

Phase I: The Prodromal Phase

The first clinical phase after radiation exposure is the prodromal period, lasting only 24-48 hours. The severity is directly related to the intensity of the exposure. Local radiation exposure may result in skin erythema similar to that seen with sunburn. Alternatively, parathesics or sensory changes may occur in the exposed area.

Phase II: The Latent Phase

This is generally an asymptomatic period occurring after the prodromal phase and before the manifest illness. The length of this phase is quite variable and is directly related to the total dose of radiation. At high exposure levels, this interval may last only several hours whereas at lower exposure levels it may last up to three weeks.

Phase III: The Manifest Illness Phase

It is during this phase that the most severe symptoms of radiation exposure will be identified. The organ systems involved as well as the severity of the illness are related to the dose of radiation received. This phase leads to either recovery or death.

Phase IV: Recovery or Death

It is during this phase that the patient either recovers from injury or succumbs to its effects. Recovery is on the order of months with slow wound healing and gradual return of normal hematological parameters. Long-term effects are not seen during this period but may take years to manifest themselves.

Acute Radiation Syndrome

One of the first tasks in evaluating a patient for acute radiation syndrome is to categorize the level of injury. This categorization may be done by exposure if the exposure level is known, or by clinical symptoms if the exposure level is uncertain.

To some degree, categorization is subjective and there is considerable overlap among the categories. The placement of patients in one or another category is useful primarily for predicting outcome. Categorization also assists the managing physician in marshaling appropriate resources to support the patient until recovery can occur. Andrews’ nomogram for hematologic injury is an example of how laboratory tests can be used to categorize patients .

Question 8-2: What treatments should be administered to victims who have experienced internal contamination?

Background: Treatment of Internal Contamination

Once radioactive materials cross cell membranes, they are said to be incorporated. Incorporation is a time-dependent, physiological phenomenon related to both the physical and chemical natures of the contaminant. The rate of incorporation can be quite rapid, occurring in minutes, or it can take days to months. Thus, time can be critical and treatment (decorporation) urgent. Several methods of preventing incorporation (e.g., catharsis, gastric lavage) might be applicable and can be prescribed by a physician. Some of the medications or preparations used in decorporation might not be available locally and should be stocked when a decontamination station is being planned and equipped.

If internal contamination is suspected or has occurred, the physician or radiation safety officer should request samples of urine, feces, vomitus, wound secretion, etc. Whole-body counting radioassay also can help evaluate the magnitude of the problem and the effect of any treatment. The contaminated patient admitted with an airway or endotracheal tube must be considered to be internally contaminated.
Reference 3 Fong and Schrader Figure I depicting Andrews nomogram

Essential Element #8: Background Supplement

Hospital Evaluation and Treatment of Radiation Exposure Victims

Treatment of Internal Contamination

Potential Contamination Situations

  • Stages of the nuclear fuel cycle:
    Fabrication of fuel elements
    Reactor operation, repair
    Decommissioning, reprocessing, and waste disposal
  • Accidental intake with radioactive sources:
    Medical
    Industrial
    Environmental uptake associated with accidental or intentional releases of radioactivity (e.g., reactor accidents, terrorist activity)

Pathways of Contamination

  • Inhalation:
    Particularly likely with explosion or fire
    Particle characteristics important (size, chemical composition, solubility in body fluids)
  • Absorption from wounds.
  • Ingestion:
    Uncommon in an industrial setting
    This pathway is critical for the general public after an accidental release into the environment.

Inhalation Pathway

  • Size of the aerosol particles determine region of the respiratory tract where most are deposited.
  • Fate of inhaled particles is dependent on their physico-chemical properties.
    1. Highly insoluble particles remain in the lung for long periods of time, depending upon where deposited in lung.
    2. A small fraction will be transported to the tracheo-bronchial lymph nodes by pulmonary macrophages.
    3. Some are cleared through the airways, swallowed, and excreted in the feces.

Nuclear Reactor Accidents

  • In the immediate vicinity of a nuclear accident (the near field), exposure could begin immediately if the released plume is at a low level. Main route of exposure is inhalation. Potentially larger thyroid doses might be expected from radioiodine.
  • Further away from the site of the accident (the far field), the main route of exposure to radioiodine would be ingestion of contaminated food and drink, particularly milk. Exposure by these routes could last longer, cover a larger area, and affect a larger population than exposure in the near field.

General Health Physics Guidelines

  • Attempt to determine the maximum credible accident.
  • Inhalation:
    Nasal swab taken within a few minutes post-exposure can aid in nuclide identification.
    Prepare for whole-body and/or lung counting.
  • Wounds:
    Use of a wound probe helpful to ascertain maximum credible accident.
    Surgical debridement sometimes helpful if decontamination efforts are unsuccessful.

Methods for Assessing Intakes

  • Whole Body Counting:
    Feasible for nuclides that emit penetrating x- or gamma rays
    Useful also for nuclides emitting energetic beta particles which can be detected by their bremsstrahlung radiation
  • Bioassay:
    Urine is most widely used
    Feces
    Excised material from wounds
  • Chromosome aberration analysis may be of some use but is rarely used

Treatment Methods

Minimize intake.
Reduce and/or inhibit absorption.
Block uptake.
Use isotopic dilution.
Promote excretion.
Alter chemistry of the substance.
Displace isotope from receptors.
Chelate.

Tritium – 3H

  • Follows pathway of water in the body.
  • Penetrates skin, lungs, and GI tract, either as tritiated water (HTO) or in the gaseous form.
  • Single exposures are treated by forcing fluids.
  • This has the dual value of diluting the tritium and increasing excretion.
  • Biological half-life is 10 days.
  • Forcing fluids to tolerance (3-4 L/d) will reduce the biological half-life to 1/3 to 1/2 of the normal value.

Uranium

  • Solubility classes:
    1. UF6 (uranium hexafluoride): Class D (days).
    2. UO2(NO3)2 – Uranyl nitrate: Class D.
    3. UO2 – Uranium dioxide: Class W,Y (weeks, years).
    4. UO2 – High-fired uranium dioxide: Class Y.
  • Inhalation is usual occupational exposure.
  • Overall biological half-life is 15 days.
  • 85% of retained uranium resides in bone.
  • Kidney toxicity is the basis of occupational exposure limits.
  • In acidic urine, uranyl ion complex with tubule surface proteins.
  • Some of the bound UO22+ is retained in the kidney.
  • Kidney is the first organ to show chemical damage in the form of nephritis and proteinuria.
  • Oral doses or infusions of sodium bicarbonate are the treatment of choice and should be dosed to keep the urine alkaline by frequent pH measurements.

Iodine

  • The dominant initial internal contaminant after a reactor accident, nuclear weapons test, or any incident involving fresh fission products is likely to be 131I.
  • Thyroid is generally blocked by dilution; 130 mg KI tablet immediately and one tablet daily x 7-14 days.
  • 5 or 6 drops of SSKI (Saturated Solution of Potassium Iodide (1 g/ml)) is another convenient way to administer stable iodide.
  • Potassium perchlorate (200 mg) may be used in patients with iodine sensitivity.

Dose of Stable Iodine to Exposed Groups

  • Consider a basic tablet giving 50 mg of I.
  • Adults: two tablets.
  • Children and adolescents: one tablet.
  • Infants: 1/2 tablet.
  • Neonates: 1/4-1/2 tablet crushed up in jam or a drink.
  • Timing: immediate. However, in a situation with continuing exposure, stable I may be 50% effective even 5 hours after exposure to radioiodine.

Exposed Population Groups

  • Pregnant women
    First trimester – In the near field, stable I will protect mother; no fetal action necessary. In the far field, maternal protection may be effected by controls on food.
    Second trimester – Fetal thyroid begins to function around the 12th week of gestation.Stable I should be given for subjects in both near and far fields to protect maternal and fetal thyroids.
    Third trimester – Same as 2nd trimester.
    vConclusions: Stable I to all pregnant women in near field for all trimesters; stable I to 2nd and 3rd trimester women in the far field.

Cesium

  • 137Cs (physical half-life, 30 years; biological half-life, 109 days) is the dominant radioisotope in aged fission products.
  • Distributes in body fluids similarly to potassium.
  • The most effective means for removing radioactive cesium is the oral administration of ferric ferrocyanate, commonly called Prussian Blue.
  • One gram orally three times daily x 3 weeks reduces the biological half-life to about 1/3 of the normal value.

Actinides

  • Plutonium, Americium, Curium, and Californium
  • All have long biological half-lives.
  • Inhalation is approximately 75% of industrial exposures.
  • If the compound is soluble (nitrate, citrate, fluoride), compound is ultimately translocated from the lungs to ultimate disposition sites (bone and liver).
  • Ca-DTPA and Zn-DTPA chelation therapy is the treatment of choice.

Chelating Agents – DTPA

  • Trisodium calcium diethylenetriaminepentaacetate (Ca-DTPA).
  • Chelating agent for transuranic elements.
  • Ca-DTPA is approximately 10 times more effective than Zn-DTPA for initial chelation of transuranics. It is the treatment of choice for initial patient management. Must be given as soon as possible after accident.
  • Repeated dosing of Ca-DTPA can deplete the body of zinc and manganese.
  • Dosage of Ca-DTPA and Zn-DTPA is 1 gm intravenously or inhalation in a nebulizer (1:1 dilution with water or saline).
  • Very safe drug with no significant adverse reactions noted during 25 years of usage.
  • Initially: 1 gm Ca-DTPA; repeat 1 gm Zn-DTPA daily up to five days if bioassay results indicate need for additional chelation.
  • Ca-DTPA: Pregnancy category D.
  • Zn-DTPA: Pregnancy category C.
  • DTPA + DFOA may be a better combination.

DTPA – Relative Contraindications

  • Pregnancy: Use first dose as Zn-DTPA instead of Ca-DTPA.
  • Diabetic on Insulin: Use Zn-DTPA and monitor glucose levels.
  • Depressed myelopoietic function: Use clinical judgment.
  • Impaired renal function: Use clinical judgment.
  • Children: Limited data available.
    Additional Chelating agents
  • Dimercaprol (BAL) forms stable chelates with mercury, lead, arsenic, gold, bismuth, chromium, and nickel. It may therefore be used for the treatment of internal contamination with radioisotopes of these elements.
  • Deferoxamine (DFOA) has been effective in treatment of iron storage disease; may be used for chelation of 59Fe.
  • Penicillamine (PCA) chelates with copper, iron, mercury, lead, gold. It is superior to BAL and Ca-EDTA for removal of copper (Wilson’s Disease).

Question 8-3: Which diagnostic tests are indicated when the patient has been exposed to ionizing radiation?

Background: Use of Laboratory Test Information

Absolute Lymphocyte Count: The absolute lymphocyte count is the first value to show any change after a significant radiation exposure. These changes occur rapidly and stabilize, reaching their nadir at three to five days post exposure. An exposure of 1.0 Gy will decrease lymphocyte counts to approximately 75 percent of their normal value. 2.0 Gy will cause a decrease in lymphocyte counts to approximately 50 percent of normal value, and 5.0 Gy will result in lymphocyte counts being approximately 10 percent of normal. Radiation exposures of greater than 5.0 to 6.0 Gy will result in lymphocytes being absent or minimally detected. This is exceedingly important dosimetric information, since the absolute count of lymphocytes can be used to estimate exposure. Lymphocyte levels remain depressed for four to six weeks before starting to return to normal. Six months later, normal values should be detected.

Care must be taken in using the lymphocyte value to determine whether or not a patient has had radiation exposure if he has the prodromal symptoms. Influenza can result in diminished lymphocyte counts as well. Usually viral illnesses with lymphopenia will be present with atypical lymphocytes in contrast to radiation exposure. Severe depression of lymphocyte counts, however, is not a normal feature of viral illness and may be an indication of significant radiation exposure.

Change of Lymphocyte Counts (G/L) in the Initial Days of Acute Radiation Syndrome Depending on the Dose of Acute Whole Body Exposure
From reference 9(p.17)

Neutrophil Count: The neutrophil count is the best predictor of subsequent clinical infection. Exposures in the range of 1.0 Gy result in only a mild decrease of the neutrophil count. Exposures of up to 2.0 Gy will result in a 50 percent decrease in the neutrophil count. In contrast to the lymphocyte count, the decrease in neutrophils is gradual, reaching its nadir at four to six weeks post exposure. At greater exposures 2-6 Gy the neutrophil count may actually rise in the first several days followed by a fall. This fall may be quite precipitous, dropping to 50 percent or less of normal counts by one-week post exposure. In a patient with more significant radiation exposure, there may be a plateauing of the neutrophil counts or even a transient rise at one to two weeks. This is almost invariably followed by a further decrease in the neutrophil count. If the patient survives, recovery of neutrophils is noted between the sixth and eighth weeks post exposure. As in chemotherapeutic regimens, patients should receive appropriate 3 antibiotic coverage and isolation when the neutrophil counts become dangerously low. Susceptibility to opportunistic organisms may occur in this population as well.

Platelet Count: As with the other formed blood elements, the effect on platelet count is related to the exposure level. Larger exposures will result in a decrease in the platelet count beginning within the first week or two-post exposure. Lower levels of exposure will manifest changes at four weeks.

Essential Element #8

Hospital Evaluation and Treatment of Radiation Exposure Victims

Timeline


Planning Guidelines

1. Determine level of exposure once victims are medically stable.
2. Decide which victims will require decorporation measures.
3. Establish admission or referral criteria for victims.

Essential Element #9

Liaison with In-Country Public Health Officials and International Health Organizations

Question 9-1: When should local public health officials be notified of a radiation accident and what issues need to be discussed?

Background: Reporting requirements following the unauthorized release or exposure to radiation by workers in the radiation industry or the general public may vary from country to country. Public health officials should help estimate the risk of the spread of radioactive contaminants in the environment, the need for population evacuation and the administration of counter measures to block the uptake of radioactive materials into body organs.

Question 9-2: When should international health organizations be notified of a radiation accident and what assistance should be considered?

Background: The IAEA and WHO are available 24 hours/day to assist with the management of radiation incidents. IAEA member states are signatory to the “Convention on Assistance in the Case of a Nuclear Accident or Radiological Emergency,” which is a standing legal system establishing notification and assistance protocols and procedures. IAEA and WHO are organizations that have access to radiation health experts who are available to consult with on-scene public health and medical personnel.

Essential Element #9

Liaison with In-Country Public Health Officials and International Health Organizations

Planning Guidelines

1. Establish by protocol who should be contacted regarding a radiation accident and what information should be provided.
2. Determine by protocol how and when international assistance will be accessed.

Essential Element #10:

Public Relations and Media Interaction

Question 10-1: What are the best guidelines to follow with regard to informing the public about accidents involving radiation release or exposure?

Background: Once the information is available, accurate data about the nature of the incident, the number of victims involved, the potential for further involvement and the interventions in progress need to be released. News releases need to be updated at regular intervals. The data must be provided by highly credible individuals who have interacted with members of the Medical Command Team.

Question 10-2: How can the media be used to assist with overall radiation accident response?

Background: The media can help responders by disseminating information concerning ongoing health risks and possible treatments for the general public (i.e., contamination of food, water and the environment). Evacuation plans and the location of temporary shelter can also be commentated by television, radio and newspaper.

Essential Element #10

Public Relations and Media Interaction

Timeline

Planning Guidelines

1. Train some members of the Medical Scene Command Team to interact with reporters and public officials seeking information about victims.
2. Be prepared to ask the media for assistance in spreading important announcements.

Essential Element #11

Data Management and Medical Record Keeping

Question 11-1: How should Medical Scene Command personnel keep track of victim management activities?

Background: Initially, medical response personnel should identify injured victims using triage tags also used for disaster response. Standardized reporting forms that track victim radiation surveys, medical evaluation, and treatment are highly desirable. Diagrams, photos or videotapes are helpful, visual records of the progression of the victim’s clinical picture. All data collected should be incorporated into the victims’ permanent medical record to facilitate long-term surveillance of survivors. Sample tags and forms were discussed in previous sections of this document (see Essential Elements #5 and #7).

Question 11-2: How can victim-related data be shared between countries and international health organizations?

Background: Electronic transmission of data via the Internet and telecommunication software can be used during a radiation accident to monitor victim treatment and situation control activities.

Essential Element #11:

Data Management and Medical Record Keeping

Timeline

Planning Guidelines

1. Develop triage tags and standard victim tracking forms for radiation accidents.
2. Acquire and test communication networks within the country and with international health organizations that may be of assistance.

Essential Element #12:

Withdrawal of Medical Personnel from the Radiation Accident Site

Question 12-1: When do medical responders withdraw from the scene of a radiation accident?

Background: Prior to withdrawal, search and rescue personnel should accompany medical personnel (wearing proper protective clothing if indicated) to all areas where victims may have been located. If some victims may be trapped it may be necessary to use dogs trained to smell for victims, or microphones to probe the collapsed areas. Responders should complete external decontamination and remove protective clothing before departing the scene. Dosimeters should be evaluated by a health physicist.

Question 12-2: What public health issues must be considered as part of withdrawal from the scene of a radiation accident?

Background: Public health personnel must be sure that all radiation sources have been contained or removed from areas that may be visited by the general public. Information should be provided regarding the potential for harmful exposure if individuals try to re-enter the accident area.

Essential Element #12

Withdrawal of Medical Personnel from the Radiation Accident Site

Timeline

Planning Guidelines

1. Determine how Medical Scene Command will decide when it is safe to consider withdrawing rescue personnel.
2. Develop a plan to assure that no victims have been missed because of their location or need for extrication.
3. Assure the public that areas near the accident scene are safe for re-entry or prohibit individuals from returning to contaminated areas.

Essential Element #13:

Responder Debriefing

Question 13-1: What concerns of responders must be addressed at the conclusion of a radiation accident response?

Background: Following an accident, responding personnel will be fatigued and emotionally drained. Trained counselors should be available to help them manage physical and emotional stress related to the types of injuries treated and the fears that may lead to illness that personnel experience during the response.

Timeline

Planning Guidelines

1. Identify medical personnel who were involved in the management of victims in the field and in the Emergency Department.
2. Assure that the identified individuals are assessed for evidence of emotional stress by individuals trained in critical incidence stress debriefing (CISD).

Essential Element #14:

Planning for Future Response

Question 14-1: What planning activities should occur in the days and months following a radiation accident response?

Background: Responders should meet to identify the lessons learned from the accident. The successful solutions to logistic problems should be included in plan revisions.

Question 14-2: In addition to planning for improved future response, what other factors should be considered?

Background: Studying prior radiation accidents allows public health officials and municipal planners to figure out ways to prevent future occurrences of the same kind. Through international health organizations, lessons learned from disaster plans to mitigate the impact of disasters can be shared by officials in all interested countries.

Timeline

Planning Guidelines

1. Command personnel should schedule CISD meetings and meetings for review of victim management protocols prior to relieving disaster personnel at the end of a response.

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of BU School of Medicine