Acute radiation syndromes are dependent on the total body dose received, and are divided into haemotological, gastrointestinal, cutaneous and central nervous system / cardiovascular. Each syndrome has a prodromal phase (usually with nausea, vomiting and diarrhoea), a latent phase, a ‘manifest illness’ phase and then either death or recovery.
This syndrome occurs with whole body doses from 0.7 Gy to 10 Gy. The prodromal phase occurs within hours to days, lasts for minutes to days, and includes anorexia, nausea and vomiting. This is followed by a latent phase of 1 – 6 weeks, where the patient feels well, during which their stem cell population dies off.
The manifest illness phase begins with pancytopenia, leading to haemorrhage, infection and fatigue. Death commonly occurs due to infection or bleeding, usually within a few months of exposure. The death rate increases with dose. Recovery takes months up to 2 years. The LD50/60 (lethal dose to kill 50% of the population at 60 days) is between 2.5 and 5 Gy.
This syndrome occurs with whole body doses from 10 to 100 Gy. The prodromal phase occurs within a few hours of exposure, characterised by nausea, vomiting and diarrhoea. Anorexia and crampy abdominal pains are common. This phase usually lasts for 2 – 3 days. The latent phase lasts less than a week, and the patient may feel well at this time despite loss of most cells lining the gastrointestinal tract.
The manifest illness phase features a return of the prodomal symptoms, leading to dehydration and electrolyte disturbance. Death occurs due to these problems or infection, within 2 weeks. The LD100 (lethal dose to kill 100% of the population) is 10 Gy.
Central Nervous System / Cardiovascular Syndrome
This is the most rapid of the acute radiation syndromes, occurring with doses over 50 Gy. The prodromal phase begins within minutes of exposure, featuring the usual gastrointestinal symptoms as well as nervousness, confusion or loss of consciousness. This phase lasts from minutes to hours. The latent phase is not always a feature, and the patient may regain limited functionality for several hours at most. Watery diarrhoea, convulsions and coma herald the manifest illness phase, which begins about 5 – 6 hours following exposure and leads to death within 3 days. There is no recovery from this syndrome.
Although skin reactions are seen in other syndromes, the concept of a cutaneous syndrome as a distinct entity has been created to cover situations where the skin of a patient is treated with sparing of deep structures. This may occur with exposure to electron radiation or the wearing of contaminated clothing. The prodromal phase is characterised by erythema and itching, and may last for days. The latent phase may last for several weeks. Moist desquamation, loss of hair, skin ulceration and necrosis may occur in the manifest illness phase. The skin typically heals after several more weeks, although severe cases will be left with permanent skin atrophy, epilation and possible necrosis.