Radiation Sickness and Radiation Injury
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Direct answer
Radiation sickness, or acute radiation syndrome, is the illness that follows high-dose exposure to ionising radiation, and its form depends on the dose received. The haematopoietic syndrome appears at lower doses, the gastrointestinal syndrome at higher doses, and the cerebrovascular or CNS syndrome at the highest doses. Once life-threatening injuries are stabilised, management proceeds to removing contaminated clothing and washing the skin, followed by supportive care and specific agents for internal contamination.
What you must remember
- Haematopoietic syndrome: appears from about 1 Gy of whole-body exposure, with early lymphocyte depletion, then pancytopenia, infection and bleeding after a latent period.
- Gastrointestinal syndrome: follows exposure above roughly 6 Gy, with mucosal loss, severe diarrhoea, fluid and electrolyte loss and sepsis.
- CNS syndrome: seen at the highest doses, typically above about 20 Gy, with neurological signs and seizures within hours to days.
- Prodrome: early nausea and vomiting, and the earlier and more severe they are, the higher the dose.
- Latent period: a symptom-free interval of days to weeks before the manifest illness.
- Decontamination: clothing is removed, skin and hair are washed with soap and water, and contaminated items are bagged.
- Blocking and decorporation: potassium iodide blocks thyroid uptake of radioiodine, Prussian blue is used for caesium, and DTPA for plutonium and americium.
A triage pathway after a radiation exposure
A radiation incident is managed in a fixed order, so that staff are protected and the patient is treated for the syndrome that the dose predicts. The steps below run from confirming the exposure to long-term follow-up.
- Confirm the exposure. Establish whether the event was external irradiation, contamination or both, and check any dosimeter readings.
- Triage by early symptoms. Time to vomiting and the early lymphocyte count estimate the dose and guide the prognosis.
- Decontaminate. Clothing is removed and contaminated items are bagged, which protects staff and limits internal uptake.
- Give specific decorporation. Potassium iodide, Prussian blue or DTPA is chosen according to the isotope involved.
- Support the organ syndrome. Fluids and electrolytes treat gastrointestinal loss, antibiotics and transfusion treat marrow failure, and growth factors are used where indicated.
- Plan long-term follow-up. Blood counts are monitored, and survivors are screened for late cancers and lens opacities.
Where the exam tries to catch you
Questions test whether the syndrome is predicted by dose and whether contamination is separated from exposure.
- Trap: A person exposed to external radiation must be isolated because they are radioactive. Correct: external exposure does not make a person radioactive, whereas contamination can spread and needs decontamination.
- Trap: Potassium iodide protects against all radioactive contamination. Correct: it blocks only thyroid uptake of radioiodine, so the isotope must be identified first.
- Trap: The gastrointestinal syndrome appears at the lowest doses. Correct: the haematopoietic syndrome appears first at the lowest doses, and the gastrointestinal form follows at higher doses.
Indian viva questions often link these facts to the Atomic Energy Regulatory Board's role in radiation safety.
Frequently asked questions
Which dose range causes the haematopoietic form of acute radiation syndrome?
The haematopoietic syndrome occurs from about 1 Gy of whole-body exposure upwards, with early lymphocyte depletion as a marker. It is managed with supportive care and growth factors, and it is the form most amenable to treatment.
Which decorporation agent is given for radioiodine contamination?
Potassium iodide is given to block the thyroid uptake of radioiodine. It must be started promptly, and it protects only the thyroid, not the rest of the body.
What is the first step in managing a radiation-contaminated patient?
Removing clothing and washing the skin and hair with soap and water is the first step in managing a radiation-contaminated patient. This reduces skin contamination and internal uptake, and it protects staff before specific decorporation agents are given.
Why is early vomiting after radiation exposure clinically significant?
Early vomiting after radiation exposure suggests a higher dose, and the time to its onset helps estimate the severity of acute radiation syndrome. This early phase, called the prodrome, is therefore used in triage.
What does the gastrointestinal syndrome of radiation injury involve?
The gastrointestinal syndrome follows exposure above roughly 6 Gy and involves mucosal loss, severe diarrhoea, fluid and electrolyte loss and sepsis. Management relies on fluid replacement, antibiotics and intensive supportive care.