Acute Radiation Syndrome; Clinical features and triage

Iraj Nabipour, MD

The Persian Gulf Health Research Center, Bushehr University of Medical Sciences

e.mail:nabipour@bpums.ac.ir

Acute radiation syndrome (ARS) is an acute illness caused by irradiation of the whole body (or a significant portion of it). It follows. It follows by a high dose of penetrating radiation (high energy X-rays, gamma rays, and neutrons) in a very short period of time (usually a matter of minutes). The major cause of this syndrome is depletion of immature parenchymal stem cells in specific tissues. The prodromal  phase may occur within hours after exposure and is characterized by anorexia, nausea and vomiting. In this phase of acute radiation syndrome, laboratory evidence of haematopoietic damage can already be observed after an exposure of about 0.5 Gy. There is usually a remission in the symptoms, allowed by a relatively asymptomatic latent phase that lasts one to three weeks. The latent phase is followed by the critical phase. The three classic ARS Syndromes are: 1) Hematopoietic syndrome-characterized by deficiencies of WBC, lymphocytes and platelets, with immunodeficiency, increased infectious complications, bleeding, anemia, and impaired wound healing. 2) Gastrointestinal syndrome: The full syndrome will usually occur with a dose between 10 and 100 Gy though some symptoms may occur as low as 6 Gy. Destructive and irreparable changes in the GI tract and bone marrow usually cause infection, dehydration, and electrolyte imbalance. 3) Cardiovascular/ Central Nervous System syndrome: Primarily associated with effects on the vasculature and bresultant fluid shifts. Signs and symptoms include vomiting and diarrhea within minutes of exposure, confusion, disorientation, cerebral edema, hypotension, and hyperpyrexia.

Triage of ARS: a) Secure ABCs (airway, breathing, circulation) and physiologic monitoring (blood pressure, blood gases, electrolyt and urine output) as appropriate b) Treat major trauma, burns and respiratory injury if evident c) Obtain blood samples for CBC, with attention to lymphocyte count, and HLA typing prior to any initial transfusion and at periodic intervals following transfusion. d)Treat contamination as needed. e) If exposure occurred within 8 to 12 hours, repeat CBC, with attention to lymphocyte count, 2 or 3 more times (approximately every 2 to 3 hours) to assess lymphocyte depletion.