Radiation Exposure

Expanded use of ionized radiation has vastly increased the incidence of radiation exposure. Cancer patients who receive radiation therapy and nuclear power plant workers are among the most likely victims of radiation exposure.

The amount of radiation absorbed by a human body is measured in radiation absorbed doses (rad), not to be confused with roentgens, which are used to measure radiation emissions. A person can absorb up to 200 rad without fatal consequences. A dose of 450 rad is fatal in about half the cases; more than 600 rad is almost always fatal. When radiation is focused on a small area, the body can absorb and survive many thousands of rads if they're administered in carefully controlled doses over a long period of time. This basic principle is the key to safe and successful radiation therapy.

Causes

Exposure to radiation can occur by inhalation, ingestion, or direct contact. The existence and severity of tissue damage depend on the amount of body area exposed (the smaller, the better), length of exposure, dosage absorbed, distance from the source, and presence of protective shielding.

Ionized radiation (X-rays, protons, neutrons, and alpha, beta, and gamma rays) may cause immediate cell necrosis or disturbed deoxyribonucleic acid synthesis, which impairs cell function and division.

Rapidly dividing cells - bone marrow, hair follicles, gonads, and lymph tissue - are the most susceptible to radiation damage; highly differentiated cells - nerve, bone, and muscle - can resist radiation more successfully.

Symptoms

• Nausea and vomiting
• Diarrhea
• Sloughing of skin
• Open sores on the skin
• Hair loss
• Ulceration of the oral mucosa
• Bloody stool
• Weakness, fatigue, exhaustion, fainting

Diagnostic tests

Supportive laboratory findings show decreased hematocrit, hemoglobin, and platelets; thrombocytopenia, leukopenia, and lymphopenia; and decreased levels of serum electrolytes (potassium and chloride) from vomiting and diarrhea. Bone marrow studies show blood dyscrasia; X-rays may reveal bone necrosis. A Geiger counter may help determine the amount of radiation in open wounds.

Treatment

Initial treatment of a patient exposed to radiation involves managing any life-threatening injuries. After the patient's airway, breathing, and circulation are secure, a Geiger counter helps determine whether radio­active material was ingested or inhaled. Treatment for local radiation depends on the extent, degree, and location of tissue injury. Treatment for systemic effects is symptomatic and supportive.

Chelating agents are used to remove internal radio­active contamination. If contamination remains, the patient's wounds are cleaned, irrigated, debrided, and left open for 24 hours. With severe contamination­amputation, although rare, may be required.

Prevention

• Avoid unnecessary exposure to radiation sources.
• Always use "shields" over parts of the body not being treated or studied when receiving x-rays or radiation treatments.

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