Acute Radiation Syndrome (ARS) (sometimes known as radiation toxicity or radiation sickness) is an acute illness caused by irradiation of the entire body (or most of the body) by a high dose of penetrating radiation in a very short period of time (usually a matter of minutes).
The three classic ARS Syndromes are:
Bone marrow syndrome (sometimes referred to as hematopoietic syndrome): The survival rate of patients with this syndrome decreases with increasing dose. The primary cause of death is the destruction of the bone marrow, resulting in infection and hemorrhage.
Gastrointestinal (GI) syndrome: Survival is extremely unlikely with this syndrome. Destructive and irreparable changes in the GI tract and bone marrow usually cause infection, dehydration, and electrolyte imbalance. Death usually occurs within 2 weeks. Damage to the gastrointestinal tract is one of the primary causes of morbidity and mortality following radiation exposure.
Cardiovascular (CV)/ Central Nervous System (CNS) syndrome: Death occurs within 3 days. Death likely is due to collapse of the circulatory system as well as increased pressure in the confining cranial vault as the result of increased fluid content caused by edema, vasculitis, and meningitis.