Acute Radiation Syndrome

Aka: Acute Radiation Syndrome, Radiation Syndrome, Radiation Poisoning, Radiation Sickness, Radiation Toxicity, Radiation Injury, Ioninzing Radiation Injury, Radiation Sickness Syndrome, Radiation-Induced Disorder

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II. Definitions

  1. Radiation
    1. Energy transmitted from a source through space or objects
  2. Ionizing Radiation
    1. Electromagnetic waves or subatomic particles with energy levels capable of removing electrons from atoms
    2. Examples include higher energy forms of UV light, gamma rays and xrays
    3. Nuclear materials emit ionizing radiation
  3. Non-ionizing Radiation
    1. Lower energy sources that do not cause ionization of atoms (loss of electrons)
    2. Examples include visible light, laser, infrared light, microwaves, radio waves and low level UV light
  4. Acute Radiation Syndrome
    1. Radiation exposure resulting in severe, specific organ injury with risk of death within hours to months
  5. Radiation-Induced Multiorgan Failure
    1. Progressive dysfunction of 2 or more organ systems over time as a result of ionizing radiation exposure
  6. Radiation Combined Injury
    1. Radiation Injury AND blunt Trauma, Penetrating Trauma, Burn Injury, Blast Injury or infection

III. Pathophysiology

  1. Body tissues with high cell turnover (high mitotic index) are most susceptible to ionizing radiation
    1. Bone Marrow
    2. Gastrointestinal Tract
    3. Skin
  2. Radiation particle type dictates the cell targets and degree of injury
    1. Alpha Particles (e.g. Radon Gas)
      1. Composed of 2 protons and 2 neutrons, with low penetration (blocked by clothing)
      2. Injury is by inhalation with alveolar injury or ingestion with intestinal mucosa injury
      3. Associated with secondary cancer development
    2. Beta Particles (e.g. nuclear power plants, medical nulcear material)
      1. Composed of electrons, with higher penetration than alpha particles
      2. Risk of Skin Injury, ingestion and inhalation
    3. Gamma Rays (e.g. nuclear explosion)
      1. Mass-less rays with high penetration
  3. Radioactive material exposure types
    1. Direct exposure (e.g. nuclear explosion)
    2. Contamination (e.g. ingestion of contaminated food or water)
  4. Radiation exposure levels correlate with effects and mortality
    1. Dose reflects whole body or significant partial body radiation exposure
    2. Dose >1 Gy
      1. Threshold for Acute Radiation Syndrome
    3. Dose >2 to 3 Gy
      1. Hematopoietic Syndrome
    4. Dose 3.5 to 4 Gy
      1. Lethal Dose in 50% of patients within 60 days (LD50/60) without supportive care
      2. With general supportive care LD50/60 increases to 4.5 to 7 Gy
      3. With rapid Intensive Care, reverse isolation, Bone Marrow TransplantLD50/60 increases to 7 to 9 Gy
    5. Dose >5 to 12 Gy
      1. Gastrointestinal Syndrome
    6. Dose >10 to 12 Gy
      1. Uniformly lethal dose
    7. Dose >10 to 20 Gy
      1. Cerebrovascular Syndrome

IV. HIstory

  1. Location of exposure in relation to radiation source
  2. Injuries related to exposure (including burn injuries)
  3. Dose of exposure
    1. High dose rate (high dose over short period) is associated with increased injury
    2. Dose rate decreases by the square of the distance from the source
    3. Shielding reduces exposure

V. Findings: Acute Radiation Syndrome

  1. Prodromal Phase (0 to 2 days after exposure)
    1. Symptoms reflect severity of exposure
      1. Lower dose exposures (<1 Gy) may be associated with mild or absent symptoms
      2. Significant, potentially lethal exposures (>2 Gy) are associated wih symptoms in the first 2 hours
      3. Highly lethal doses (>10 to 20 Gy) are associated with symptom onset within minutes of exposure
    2. Anorexia
    3. Nausea
    4. Vomiting
    5. Diarrhea
    6. Fever
    7. Tachycardia
    8. Headache
    9. Apathy
  2. Latent Phase (2 to 20 days after exposure)
    1. Symptoms temporarily abate during latent phase
  3. Manifest Illness (21 to 60 days after exposure)
    1. Severe, often life-threatening effects of organ dysfunction
    2. Findings specific to the associated syndrome (see below)

VI. Findings: Associated Syndromes

  1. Cutaneous Syndrome
    1. See Burn Injury
    2. Prodromal findings (within 1-2 days)
      1. Skin erythema and edema
      2. Desquamation (dry or moist)
      3. Bullae
      4. Skin Ulceration (may affect deep tissue down to Muscle or bone)
      5. Onycholysis
    3. Manifest Illness
      1. May be delayed years
  2. Hematopoietic Syndrome (Dose >2 to 3 Gy)
    1. Prodromal Findings
      1. Lymphopenia (see labs above)
      2. Neutropenia and Thrombocytopenia nadir at 2 to 4 weeks, but may persist months
      3. Anemia (also compounded by gastrointestinal Hemorrhage)
    2. Manifest Findings (over weeks to months)
      1. Bone Marrow aplasia or hypoplasia
      2. Pancytopenia
      3. Immunocompromised
      4. Poor Wound Healing
      5. Increased bleeding risk
  3. Gastrointestinal Syndrome (Dose >5 to 12 Gy)
    1. Onset within 5 days of exposure
    2. Mild GI symptoms (Nausea, Vomiting) are seen at low dose exposures (<1.5 Gy) in prodromal phase
    3. High dose exposures (>5 Gy) are associated with loss of intestinal crypt cells and mucosal barrier
    4. Prodromal Findings
      1. Crampy Abdominal Pain
      2. Diarrhea
      3. Nausea and Vomiting
      4. Gastrointestinal Bleeding
    5. Manifest Findings (typically after day 7)
      1. Vomiting
      2. Severe Diarrhea
      3. Malnutrition
      4. High fever
      5. Sepsis
      6. Bowel wall necrosis, perforation, ileus
  4. Cerebrovascular Syndrome (Dose >10 to 20 Gy)
    1. Associated with capillary injury at blood brain barrier, Cerebral edema and Meningitis
    2. Findings
      1. Severe Nausea and Vomiting
      2. Headache
      3. Altered Mental Status
      4. Seizures
      5. Ataxia
      6. Decreased Deep Tendon Reflexes

VII. Labs

  1. See Unknown Ingestion
  2. ABO Type and Screen
  3. Serum Electrolytes
  4. Mouth and nasal swabs for radiation testing
  5. Complete Blood Count (CBC) with differential
    1. Repeat CBC every 6 to 12 hours
    2. Observe for decreased White Blood Cells (esp. Absolute Lymphocyte Count)
      1. Absolute Lymphocyte Count depletion course best predicts exposure and prognosis
      2. Lymphocyte Count >1000 is associated with a better prognosis
        1. Lymphocyte Count maintained at 50% of normal in first week suggests <1 Gy exposure
      3. Lymphocyte Count <500 is associated with very poor prognosis (highly lethal if <100)
        1. High dose exposure (>5 Gy): 50% Lymphocyte drop in 24 hours, and more severe drop in 48 hours

VIII. Management

  1. Staff should use appropriate Personal Protective Equipment (PPE)
  2. Consult nuclear exposure experts
  3. Decontamination
    1. Remove all clothing (removes 70-90% of contaminants)
    2. Wash skin
      1. See Skin Decontamination
    3. Consider chelating agents (e.g. DTPA, Prusssian Blue, Calcium Phosphate, aluminum phosphate)
  4. Thyroid Cancer Risk
    1. Risk of Radioactive Iodine uptake in children and pregnant women
    2. Give prophylactic Potassium iodide to patients at risk
      1. Adult: 130 mg orally daily
      2. Child (over age 3 years old): 65 mg orally daily
      3. Infant (one month to age 3 years): 32 mg
  5. Infection Risk
    1. Perform any urgent or emergent surgery in first 24 to 36 hours
    2. Treat infections early
    3. Consider prophylactic antibiotics in Neutropenia
    4. Evaluate for CMV risk
    5. Evaluate for Pneumocystitis carinii risk (CD4 <200/ul)
  6. Treat specific injuries
    1. See Burn Management
  7. Basic Supportive Care
    1. Intravenous Fluids
    2. Anti-emetics (e.g. Ondansetron)
    3. Analgesics
    4. Maintain gastric acidity (avoid Proton Pump Inhibitors and H2 Blockers)
      1. May use Sucralfate for Stress Ulcer prevention
    5. Platelet Transfusion indications
      1. Platelet Count <20,000 (or <75,000 if perioperative)
  8. Intensive Care
    1. Acute Radiation Syndrome scoring systems are used to guide interventions
    2. Reverse Isolation (>2 to 3 Gy exposure)
    3. Cytokines
    4. Hematopoietic Stem Cell Transplant
  9. Patient Triage to three categories
    1. Recovery is expected with minimal supportive care (<1 Gy exposure)
      1. Employ basic measures as above
    2. Survival is possible with aggressive supportive care
      1. Triage to Intensive Care
    3. Expected to succumb (>10 Gy exposure, concurrent injuries or inadequate resources)
      1. Triage to Palliative Care

IX. References

  1. Acosta and Warrington (2022) Radiation Syndrome, Stat Pearls, Treasure Island, accessed 5/11/2022
  2. López (2011) Rep Pract Oncol Radiother 16(4):138-46 +PMID: 24376971 [PubMed]

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