Internal Medicine

Acute radiation syndrome (ARS)


Acute radiation syndrome (ARS) primarily refers to damage to the hematopoietic system, myeloid system, and gastrointestinal (GI) system that occur after a whole-body or significant partial-body (60%) exposure of >1 Gy total dose, delivered acutely at a relatively high-dose-rate.

The patient’s skin is burned in a pattern corresponding to the dark portions of a kimono worn at the time of the Hiroshima explosion | USGov Archives


Dose response in respect to radiation injury:

  • ARS is the host response against exogenous radiation injury, which may be fatal for the exposed person

Organ dysfunction in ARS

  • Even at low irradiation doses bone marrow stem cells will be affected, and thus neutrophils, monocytes, and erythrocytes
  • The function of organ fixed macrophages will also be harmed, which in turn will reduce outermost host defence barrier
  • Lung is the most vulnerable vital organ when exposed to acute irradiation because of the “double hit” radiation exposure, ie, a combined exposure of inhaled particles (P) and from gamma radiation (γ) similar to the rest of the body
> 20Gy dose Neurovascular syndrome onset (>10 Gy) Multiple organ failure probable death
(8–10 Gy) Consider stem cell transplant
6 Gy dose GI syndrome onset (6–7 Gy) LD50/60 with supportive care
(3–5 Gy) LD50/60 without treatment
1 Gy dose Hematopoietic syndrome onset (0–2 Gy) ∼100% survival without treatment
  • LD50/60 is defined as the dose necessary to cause death in 50% of an irradiated population in 60 days


Effect on skin:

  • Thermal burns from infrared heat radiation (seen in nuclear explosions)
  • Beta burns from shallow ionizing beta radiation (this would be from fallout particles; the largest particles in local fallout would be likely to have very high activities because they would be deposited so soon after detonation and it is likely that one such particle upon the skin would be able to cause a localised burn); however, these particles are very weakly penetrating and have a short-range.
  • Gamma burns from highly penetrating gamma radiation. This would likely cause deep gamma penetration within the body, which would result in uniform whole-body irradiation rather than only a surface burn. In cases of whole-body gamma irradiation (circa 10 Sv) caused by accidents involving medical product irradiators, some of the human subjects have developed injuries to their skin between the time of irradiation and death. In the picture to the left, the normal clothing that the woman was wearing would have been unable to attenuate the gamma radiation and it is likely that any such effect was evenly applied to her entire body. Beta burns would be likely all over the body caused by contact with fallout, but thermal burns are often on one side of the body as heat radiation does not penetrate the human body. In addition, the pattern on her clothing has been burnt into the skin. This is because white fabric reflects more infrared light than dark fabric. As a result, the skin close to dark fabric is burned more than the skin covered by white clothing.
  • There is also the risk of internal radiation poisoning by ingestion of fallout particles.
Common effects of ionizing radiation on the skin

Clinical features

Clinical stages:

  1. Prodromal stage (first 48 hours)
  2. Latent stage (up to a month)
  3. Manifest illness stage
  4. Recovery/death
Syndrome Signs and symptoms

Prodromal phase first 48 hours Latent phase lasts up to a month Manifest illness phase Final outcome: survival or death
Occurs at doses between 5 Gy and 12 Gy
Nausea, vomiting, diarrhoea, anorexia, haemorrhage, weakness through denuded areas
Loss of absorptive capacity
Increased intensity 4–8 hours
Tiredness and anorexia Vomiting and fever; progression of bloody diarrhoea to shock and death or treatment Radiation 8–30 Gy dose range cause death from gastrointestinal syndrome
High dose between 2–3 Gy and 8 Gy. Low dose (<2 Gy) radiation
Often asymptomatic
Some fatigue, fever, and bacteremia
Neutropenia (ANC < 0.5)
Fever, sepsis, haemorrhage, purpura, electrolyte disturbances, and epilation
Agranulocytosis irresponsive to GM-CSF after first cell cycle
Central nervous system No specific signs and symptoms
Unspecific fatigue, malaise, anorexia, and drowsiness
Not consistently correlated to exposed dose
Latency up to a month
Asymptomatic phase except for tiredness and weakness
Impaired cognition, disorientation, seizure, tremor, ataxia
Grand mal seizures
Irreversible brain damage secondary to continuous cramps
Pulmonary dysfunction Acute radiation pneumonitis
Cough, shortness of breath
ALI with inflammatory coagulation activation
Pulmonary edema Pneumonitis ARDS
Intubation and mechanical ventilation
Severe pneumonia
Lung fibrosis after 14–30 days from first exposure
Absolute respiratory insufficiency
Severely reduced oxygen transport capacity
Radiation damage in the patient after exposure. (A) head hair lost; (B) and (C) hands showing erythema and ulceration (days 24 and 44 after exposure, respectively); (D) extensive necrosis of the colon at the surgery. | Guo, M., Dong, Z., Qiao, J., Yu, C., Sun, Q., Hu, K., … Ai, H.-S. (2014). Severe acute radiation syndrome: treatment of a lethally 60Co-source irradiated accident victim in China with HLA-mismatched peripheral blood stem cell transplantation and mesenchymal stem cells. Journal of Radiation Research, 55(2), 205–209.



Dosimetry Methods Utility
Biological Whole-body counting Not practical, generally not available
Chromosomal aberrations (dicentrics and ring forms) The “gold standard,” however it takes 4–5 days processing time
Clinical Signs and symptoms In spite of high practicability, clinical dosimetry has low sensitivity particularly at low doses


Initial steps

  • Removing any contaminated clothing (↓ exposure by 80%)
  • Within the first hours of contamination: Nonradioactive potassium iodide (KI) (stable iodine): Saturates iodine binding sites within the thyroid and inhibits incorporation of radioiodines into the gland.
    • Special priority to mothers & children

Supportive management:

  • Fluid management and early treatment of any signs of infection
  • Prevention of thyroid cancer must be a priority
  • Stop breastfeeding (if possible)
  • Anti-emetics will be helpful to control nausea.
  • Pain control for burns and other injuries should be a priority.


  • Antibiotics, antiviral and antifungal agents for prevention or treatment of infections.
  • Moderate exposure: Granulocyte-colony stimulating factor (G-CSF) (5 μg/kg body weight/day subcutaneously)
  • Hematopoietic cell transplantation

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