Managing Acute Radiation Syndrome (ARS)

Essential Information

• ARS clinical manifestations are highly variable based on factors such as dose, dose rate, radiation quality, how much of the total body received radiation, and many host factors.
• Patients should be re-evaluated iteratively as their ARS manifestations change with time after exposure.
• Clinician decisions about specific treatments and venue referrals should always reflect individual patient factors, and the nature/size of the radiation incident. In large mass casualty incidents, recommendations may need to be modified significantly based on resource availability.
• See Disclaimers section.

• Changes in blood cell counts will reflect radiation quality, dose, dose rate, host factors, how much of the whole body receives radiation, and when, after radiation exposure ends, the CBC is obtained. Changes in blood count values can result from many other causes too.
• Lymphocytes, neutrophils, red cells, and platelets respond to radiation with different kinetics, so interpretation of lab values will depend on how long after radiation the lab values are measured. See time/dose relationship of blood count elements, Biodosimetry Tool for estimating dose from lymphocyte kinetics, and other details about the Hematopoietic Subsyndrome.
• Faster drops in absolute lymphocyte count (ALC) and absolute neutrophil count (ANC) usually reflect higher dose from exposure and more severe ARS. Granulocytosis can be an early finding after significant radiation exposure, thus complicating interpretation of early ANC values.
• If severity value for lymphocyte and neutrophil counts are widely different (e.g. H4 lymphocyte and H1 neutrophil), repeat the CBC with differential. It is probable that the low lymphocyte count (at least initially) more closely reflects the dose from exposure.
• Blood loss from the GI tract and/or damage to bone marrow elements can be seen after significant radiation exposure. Seeking the correct etiology of altered blood counts will help determine therapy recommendations.

• Nausea and/or vomiting can occur soon after brain, upper GI tract, and whole body irradiation. These are non-specific symptoms, however, as many things besides radiation can induce nausea and vomiting. Remember that even severe vomiting (e.g., G 4) can be due to stress or many causes that are not related to radiation. If nausea and vomiting are due to radiation exposure, severity and time to onset of vomiting are correlated with dose. See Biodosimetry Tool for interpreting the significance of time to vomiting.
• Altered stool consistency, diarrhea, cramps and abdominal pain, can occur after exposure of the GI tract to radiation. Severity and time of onset depend on many factors including dose.
• Radiation can cause GI mucosal damage and/or damage to the bone marrow elements. Either or both factors can contribute to GI blood loss. Seeking the correct etiology will help determine therapy recommendations.

• Severity and time of onset of radiation-induced skin changes are correlated with dose, how much skin area is irradiated, and other factors.
• Skin changes that occur earliest (hours to weeks) after exposure include erythema, swelling/edema, blistering, and alteration in skin sensitivity and/or itching in irradiated areas.
• Skin changes that tend to occur somewhat later (days to weeks) after exposure include skin desquamation (wet and dry), hair loss, skin ulceration/necrosis and onycholysis (nail and nail bed changes.
• See details about Cutaneous Subsyndrome.

• Nausea and/or vomiting can occur soon after brain, upper GI tract, and whole body irradiation. These are non-specific symptoms, however, as many things besides radiation can induce nausea and vomiting. Remember that even severe vomiting (e.g., G 4) can be due to stress or many causes that are not related to radiation. If nausea and vomiting are due to radiation exposure, severity and time to onset of vomiting are correlated with dose. See Biodosimetry Tool for interpreting the significance of time to vomiting. Seeking correct etiology will help determine therapy recommendations.
• Both increase and decrease in blood pressure and body temperature can occur hours after significant exposure to radiation. Changes in these vital signs can reflect many causes including CNS irradiation, clinical infection, and other causes.
• Fatigue, headache, and anorexia can occur hours to weeks after significant radiation exposure. These are non-specific findings which can result from many causes.
• Cognitive and neurological deficits can occur hours to weeks after significant exposure to CNS radiation. These are non-specific findings, however, which can result from many causes. Severity and time to onset of deficits due to radiation will reflect both dose from exposure and other clinical factors.