Overview of biologic effects of radiation, acute radiation sickness
Biological effects of radiation are dependent upon the type of exposure a person has with the duration of the exposure and intensity of the material playing a key role. We also have to include the role of personal protection such as time, distance and shielding.
Acute Radiation Sickness (sometimes called Acute Radiation Syndrome or ARS), occurs when an individual is exposed to a large amount of radiation in a short period time or a total doses greater than 100 REM (100 RAD for gamma radiation). Acute radiation sickness has a variety of clinical features; some are obvious, some not.In general, the clinical manifestations of acute radiation sickness include the following:
- changes in blood cell count, specifically lymphocytes decrease
- vascular permeability changes
- gastrointestinal irritation; nausea, vomiting, and diarrhea
- hair loss, in uneven patterns
- skin rash, skin burns, in general skin irritation
- vague symptoms such as flu-like symptoms
Acute radiation sickness has four phases and may manifest with four separate syndromes.
The four syndromes of acute radiation sickness are:
- Hematopoietic Syndrome
- gastrointestinal syndrome
- cardiovascular syndrome
- and central nervous system syndrome
- prodromal phase
- latent phase
- manifest phase (sometimes called the period of illness)
- and recovery or death
Gastrointestinal syndrome is a condition in which the epithelial lining of the G.I. system is gradually destroyed. Epithelial cells decline in results in nausea, vomiting, diarrhea, and sepsis. Sepsis is a result of the loss of protective barrier that separates normal bacteria from the bloodstream. Gastrointestinal syndrome may impact the lower G.I. or upper G.I. tract, or both. In the lower G.I. system bloody diarrhea (frank in nature) is most common.
Large doses of whole body radiation can cause Central Nervous System and Cardiovascular syndrome. Both are caused by a destruction of blood vessels and an increase in capillary permeability. Symptoms usually appear fairly rapidly and take the form of cerebral edema, pulmonary edema, cardiogenic shock, and death. Victims exposed to large amounts of whole body radiation may often die within 72 to 80 hours, often before the symptoms of G.I. syndrome or hematopoietic develop.
Acute radiation sickness may present within four distinct stages: prodromal, latent, manifest, and recovery/death. In the prodromal phase (approximately 48 hours after exposure) victims may present with:
- nausea and vomiting, diarrhea
- fatigue and headache
- fluid shifts due to increased permeability and electrolyte losses