Comprehensive guide to radiation types, clinical effects, and emergency management
There are two major types of ionising radiation with different penetration capabilities and clinical implications.
| Measurement | Definition | Conversion |
|---|---|---|
| Gray (Gy) | Amount of radiation absorbed by cells | 1 Gy = 100 rad |
| Rad | Traditional unit of radiation dose | 100 rad = 1 Gy |
Assume both external and internal contamination when responding to disasters involving radioactive agents.
Radioactivity can easily be detected with:
The medical effects of radiation include focal tissue damage and necrosis, acute radiation syndrome (ARS), and long-term effects that can persist for weeks to decades, such as thyroid cancer, leukaemia, and cataracts.
ARS develops acutely (within several seconds to several days) after exposure to penetrating ionising radiation above whole-body doses of 1 Gy (100 rads). The higher the exposure, the earlier symptoms will appear and the worse the prognosis.
| Phase | Timing | Symptoms |
|---|---|---|
| Prodromal Phase | 0-48 hours | Nausea, vomiting, diarrhoea, fatigue |
| Latent Phase | Hours to weeks | Relatively asymptomatic, fatigue, bone marrow depression |
| Manifest Illness | Days to weeks | Gingival bleeding, epistaxis, petechiae, systemic infections, gastrointestinal symptoms |
| Recovery/Death | Weeks to months | Resolution or progression to multi-organ failure |
Critical Indicator: A reduced lymphocyte count within 48 hours is a clinical indicator of radiation severity and prognosis.
Radiation Exposure Recommendations:
All staff dealing with contaminated patients should wear protective clothing and carry a personal radiation meter.
On-scene decontamination is usually not possible if large numbers of people have been affected. By removing clothes, up to 90% of contamination is removed.
Important: Do not abrade the skin barrier during decontamination. All contaminated materials and water must be disposed of appropriately as radioactive waste.
The ED receiving patients should be divided into contaminated and clean areas. Safe transfer can be achieved by wrapping patients in sheets to limit cross-contamination.
The aim is to reduce overall radiation dose through various strategies depending on the radioactive substance involved.
| Strategy | Mechanism | Examples |
|---|---|---|
| Reduction of absorption | Prevent uptake from GI tract | Aluminum hydroxide for strontium |
| Dilution | Increase fluid intake | Water for tritium |
| Blocking | Block receptor sites | Potassium iodide for radioiodine |
| Displacement | Replace with non-radioactive isotopes | Calcium for strontium-90 |
| Chelation | Bind and enhance excretion | DTPA for plutonium, americium |
| Decorporation | Remove internal contamination | Prussian blue for caesium |
Critical Timing: Potassium iodide must be administered within 4 hours of exposure to be effective in preventing radioiodine accumulation in the thyroid gland.