Acute Radiation Syndrome (ARS) is a severe acute illness caused by irradiation of the majority of the body by a high dose of ionizing radiation within a brief timeframe (CDC, 2017). According to the National Council on Radiation Protection and Measurements (NCRP), ARS is defined as “[…]a broad term used to describe a range of signs and symptoms that reflect severe damage to specific organ systems and that can lead to death within hours or up to several months after exposure.” (Acosta et al., 2017). The disease is characterized by depletion of immature stem cells in specific functional tissues exposed to ionizing radiation (CDC, 2017). Hazardous sources of ionizing radiation can include faults in medical imaging technology, a nuclear plant meltdown, or an attack using a nuclear weapon. People within the vicinity of these events become exposed to large amounts of radiation, causing ARS (Acosta et al., 2017).
The severity of ARS is directly linked to radiation dose, with higher doses leading to damage of more sensitive organ systems. Upon contact with intracellular targets or other molecules in the body, ionizing radiation produces free radicals which themselves become highly damaging on interaction with other molecules or tissues. The cells most critically affected by radiation are those which rapidly develop and divide, including hematopoietic stem cells (HSC) in the bone marrow, spermatocytes in the testes, and crypt cells in the intestines (López et al., 2011).
There are several factors which determine the lethality of ionizing radiation, including: dose rate, distance from the radiation source, and shielding. Receiving the same dose of radiation concentrated over a shorter period causes more damage to tissues, but the overall dose rate decreases as the distance from the source increases. Shielding can reduce exposure, depending on the shielding material (López et al., 2011).
As ARS affects multiple organ systems in the body, current treatment and standards of care (SoC) for ARS depend on the affected tissues. The most immediate goals of patient management involve physical exam, removal of external contamination, radiation dose estimation, supportive care (including psychological support of the patient and family), symptomatic treatment, blood transfusions as needed, and replacement of fluids and electrolytes (CDC, 2017). Treatment with certain cell signaling factors known as cytokines such as granulocyte colony stimulating factors (G-CSF) and keratinocyte growth factor may be used to treat other manifestations of radiation exposure (Choi et al., 2017). When required, surgical intervention must be carried out within the first 36-48 hours from exposure, since immunosuppression caused by the radiation increases risk for infection (López et al., 2011). Although ARS is extremely rare in the United States, historical cases of mass radiation exposure serve as an important reminder to prepare for the possibility for ARS in the future.
References
Acosta, R., & Warrington, S. J. (2017). Radiation, Syndrome Acute. In StatPearls. Treasure Island (FL): StatPearls Publishing
StatPearls Publishing LLC.
CDC. (2017). Acute Radiation Syndrome: A Fact Sheet For Clinicians. Retrieved February 23, 2018 https://emergency.cdc.gov/radiation/arsphysicianfactsheet.asp
Choi, J.-S., Shin, H.-S., An, H.-Y., Kim, Y.-M., & Lim, J.-Y. (2017). Radioprotective effects of Keratinocyte Growth Factor-1 against irradiation-induced salivary gland hypofunction. Oncotarget, 8(8), 13496-13508. doi:10.18632/oncotarget.14583
López, M., & Martín, M. (2011). Medical management of the acute radiation syndrome. Reports of Practical Oncology and Radiotherapy, 16(4), 138-146. doi:10.1016/j.rpor.2011.05.001
RCR. (2016). Radiotherapy dose fractionation, second edition.
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