Makindo Medical Notes

Acute radiation syndromes occur when radiation exposure damages actively dividing cells, as they are more sensitive to radiation than fully differentiated cells. These syndromes typically result from the inability of precursor cells to replace functional cells within an organ when needed. Acute radiation syndromes progress through four stages: prodromal, clinical latency, manifest illness, and either recovery or death.

Stages

• Prodromal Stage:The prodromal (early) symptoms appear shortly after radiation exposure, with the severity, duration, and onset determined by the radiation dose. Common prodromal symptoms include nausea, vomiting, anorexia, fatigue, diarrhoea, abdominal cramping, and dehydration. At very high doses, symptoms can occur within minutes; at lower doses, symptoms may take hours or may not occur at all.
• Latency Period: Following the prodromal stage, a latency period typically precedes the onset of manifest illness. During this period, the effects of the radiation on specific systems (such as hematopoietic or gastrointestinal) remain hidden until the tissues fail to self-renew, leading to clinical symptoms after typical cellular turnover times.
• Manifest Illness: Haematopoietic Syndrome: results from whole-body or significant partial-body exposure to radiation doses ranging from 3 to 9 Gy. This exposure kills mitotically active hematopoietic precursor cells, leading to symptoms caused by the depletion of circulating blood elements 4 to 8 weeks later. These symptoms may include infections, hemorrhage, impaired immune responses, and potential multi-organ failure.
• Gastrointestinal Syndrome: Gastrointestinal syndrome occurs after whole-body or significant partial-body exposure to radiation doses of about 8 Gy and higher. The radiation destroys the intestinal stem cells located in the regenerating crypts, resulting in the failure to produce new cells for the gastrointestinal lining. After a latency period of approximately 7 days, the loss or shortening of the villi on the intestinal epithelium leads to bacterial growth and increased risk of sepsis. Symptoms include anorexia, nausea, vomiting, prolonged bloody diarrhoea, abdominal cramps, dehydration, and weight loss. If death occurs, it typically happens 7 to 10 days after exposure.
• Cerebrovascular Syndrome: At extremely high radiation doses, death occurs within a few days due to cerebrovascular syndrome. This syndrome is believed to result from increased permeability of small blood vessels in the brain, leading to cerebral edema and, ultimately, death.