Acute Radiation Syndrome

Acute Radiation Syndrome from Sun YaiCheng

Units of Radiation

Exposure
Conventional unit: Roentgen

Absorbed dose
Conventional unit: rad
International system of unit: Gray
1 Gy = 100 rad

Dose equivalent
Conventional unit: Roentgen equivalents man (rem)
International system of unit: Sievert
1 Sv = 100 rem

Acute Radiation Syndrome

Stage I: Prodromal stage (chiefly gastrointestinal)

• Onset: minutes to hours (ARS is fatal if GI symptoms develop within 2-4 hrs)
• Duration: 48-72 hrs 
• Presentation: nausea, vomiting; also diarrhea, cramps

Stage II: Latent stage (chiefly hematopoietic)

• Onset: hours to days
• Duration: 1.5-2 wks
• Presentation: asymptomatic → bone marrow supression

Stage III: Manifest stage (multisystem involvement)

• Onset: 3-5 wks
• Duration: variable

• Presentation:

CNS/CVS (>15 Sv)
Cardiorespiratory/GI system (>5 Sv)
Reticuloendothelial system (>1 Sv) 

Stage IV: Recovery or Death

• Onset: weeks
• Duration: weeks to months
• Presentation: leading cause of death before recovery is sepsis

Prognosis According to the Lymphocyte Count within the First 48 Hours after Acute Exposure to Penetrating Whole-Body Radiation

MINIMAL LYMPHOCYTE COUNT PER MM2	APPROXIMATE ABSORBED DOSE (GY)	EXTENT OF INJURY	PROGNOSIS
1400–3000 (normal range)	0–0.4	No clinically significant injury	Excellent
1000–1499	0.5–1.9	Clinically significant but probably nonlethal	Good
500–999	2–3.9	Severe	Fair
100–499	4–7.9	Very severe	Poor
<100	≥8	Most severe	High incidence of death even with hematopoietic stimulation

Commonly Treated Forms of Internal Contamination

Radionuclide	Treatment	Mechanism of Action	Usual Administration
Iodine	Potassium iodide	Blocks thyroid uptake	130 milligrams PO for adults
Plutonium	Ca-DTPA or Zn-DTPA	Chelation	1 gram in 250 mL NS or 5% dextrose in water over 60 min
Tritium	Water	Dilution	Oral: 3–4 L a day for 2 wk
Cesium	Prussian blue	Decrease GI uptake	1 gram in 100–200 mL water three times a day for several days
Uranium	Bicarbonate	Alkalinization of urine	2 ampules in 1 L NS at 125 mL/h

Top 10 Key Points For Medical Management of Radiation Casualties

1. Patients should be medically stabilized from their traumatic injuries before radiation injuries are considered, then evaluated for either external radiation exposure or radioactive contamination.
2. An external radiation exposure outside the person does not make the person radioactive. Even such lethally exposed patients are no hazard to medical staff.
3. Nausea, vomiting, diarrhea, and skin erythema within 4 hours may indicate very high external radiation exposures. Such patients will show obvious lymphopenia in 8 to 24 hours. Evaluate with serial CBCs. 
4. Radioactive material may have been deposited on or in the person (contamination). More than 90% of surface radioactive contamination may be removed by removal of the clothing. Most remaining contamination on exposed skin is effectively removed with soap, warm water, and a washcloth. 
5. Protect yourself from radioactive contamination by observing standard precautions, including protective clothing, gloves, and a mask.
6. Radioactive contamination in wound or burns should be handled as if it were simple dirt.
7. In a terrorist incident, there may be continuing exposure of the public that is essential to evaluate. Initially suggest sheltering and a change of clothing or showering. Administration of potassium iodide is indicated only when there has been a confirmed release of radioiodine.
8. When there is any type of radiation incident, many persons will want to know whether they have been exposed or are contaminated. Provision needs to be made to potentially screen thousands of such persons.
9. Clinically significant acute radiation syndrome seldom if ever occurs in people receiving less than 1 Gy of whole-body radiation.
10. The principles of time/distance/shielding are key. Radiation dose is diminished by reducing time spent in the radiation area (moderately effective), increasing distance from a radiation source (very effective), or using metal or concrete shielding (less practical).

Reference

Radiation Injuries. Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 2011, pp 56-61

Disaster Management and Emergency Preparedness. Advanced Trauma Life Support, 2008, pp 333-334

Medical Treatment of Radiological Casualties: Current Concepts. Ann Emerg Med. 2005;45:643-652