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Radiological Dispersal Devices:
Medical Countermeasures

In light of the events in London, New York, Bali, Washington, D.C. and Madrid, terrorist attack has moved to the forefront of emergency department (ED) and Emergency Medical Services (EMS) planning. The use of radiologic weaponry is one threat that must be considered. In addition to attack by terrorists, preparations must also be made for a nuclear power plant disaster or contamination by radiologic medical sources. In the event of radiologic contamination, rapid treatment can be lifesaving. Properly done, rapid decontamination can reduce morbidity and mortality, limit the spread of contamination, and keep the ED functioning for the treatment of other patients.

The first step of recognizing contamination is to understand the difference between exposure to and contamination by radiologic agents. Exposure is defined by an individual's proximity to material emitting ionizing radiation. Actually touching, inhaling, or swallowing that material is contamination.

The process of decontamination can be divided into 2 stages: gross and secondary decontamination.

Gross decontamination

Gross decontamination is usually performed before the patient reaches a hospital environment. It consists of removal of the entire patient's clothing and, if possible, brief irrigation of the patient's entire body with water. Gross decontamination removes more than 95% of external contamination and renders the patient safe for access by care providers. If gross decontamination has not occurred in the field, it must be performed in a designated decontamination site by ED personnel. In the event of a mass casualty incident, gross decontamination is all that is immediately necessary.

Secondary decontamination

Secondary decontamination is a stepwise methodical cleansing of any remaining radioactive areas of the patient. The general procedure for secondary decontamination involves using a radiation detection device (RDD) to perform a head-to-toe survey of all areas of the patient's body. All secretions and runoff should be collected for sampling and dose estimation. After irrigation, the areas are surveyed again. This process is continued until acceptable levels are reached. Acceptable levels may be slightly above baseline and should be determined by treating physicians.

Internal Decontamination

Internal decontamination can be achieved by a number of methods, including the blockade of enteral absorption, blockade of end-organ uptake, dilution, and chelation. Speed is of the essence because some isotopes can be incorporated by end organs within an hour of exposure and are very difficult to remove. Therefore, EDs that are expected to care for these individuals must have the resources for internal decontamination available.

Blockade of enteral absorption

Gastric lavage and emetic agents:

Although these strategies may decrease absorption of radioisotopes if initiated early after gastric contamination, they also create the risk of aspiration of radioisotopes, leading to respiratory contamination. Some enteral binding methods have been shown to effectively bind specific agents of contamination. Examples are:

• Barium sulfate
• Aluminum and magnesium salts
• Prussian blue
• Activated charcoal

Blockade of end-organ uptake

Potassium iodide (KI): This medication has recently received much attention by the press. It is viewed by the public as a universal blocking agent for all the effects of a radiologic or nuclear attack. Radioactive iodine (RAI) is present in nuclear reactor fuel rods; therefore, in the event of any reactor accident, terrorist attack, or use of fuel rods for terrorist explosive devices (radiation dispersal devices, ie, dirty bombs), RAI can be released. The primary toxicity of RAI is to the thyroid gland. Effectiveness is directly proportional to the speed of administration, which is preferably within 6 hours of exposure. Toxicity of RAI is highest in the pediatric population, but this medication should be administered to any patient who has been contaminated. The dose is 300 mg/d by mouth for 1-2 weeks.

Calcium: Calcium gluconate or calcium chloride can be administered to limit the incorporation of strontium or radioactive calcium into bone. Patients can receive 1 g of calcium chloride or 3 g of calcium gluconate administered intravenously.

Dilution

Oral fluids: Tritium is present in nuclear weapons and is used by the military for luminescent gun sights. If internal contamination with tritium is suspected, administer copious oral or IV fluids to cause dilution and increase renal excretion of tritiated water. Oral fluid in the amount of 5-10 L/d should be administered for 1 week. Sodium monitoring is necessary if hypotonic fluids are used.

Phosphorus: Similar to dilution of tritium, oral loading with phosphorus salts (Neutra-Phos) can enhance the elimination of radioactive phosphorus. One packet of neutral phos or 2 tablets of K Phos should be administered qid by mouth for 3 days.

Chelation

Diethylenetriamine pentaacetic acid (DTPA): Americium (a daughter product of plutonium), uranium, plutonium, and other heavy metals (present in nuclear reactors and weapons) are poorly excreted by the kidneys. Pentetate calcium trisodium (CaDTPA) and pentetate zinc trisodium (ZnDTPA) form compounds with specific radioisotopes (ie, americium, curium, plutonium), rendering them more easily excreted by the kidneys and enhancing elimination. If within the first 24 hours of exposure, use Ca-DTPA. For subsequent doses, or if first treating after 24 hours of exposure, use Zn-DTPA. The dose for either agent is 1 g dissolved in 250 mL of saline or D5W given over 1 hour qd. If the exposure is solely respiratory, 1 g of either agent can be mixed 1:1 with normal saline and nebulized.

Penicillamine: Radioactive cobalt is used for medical radiotherapy and food irradiation. In the case of internal contamination caused by radioactive cobalt, similar clinical effects to DTPA administration can be achieved with the use of penicillamine. The dose is 250-500 mg by mouth 4 times per day.

Decrease organ damage

Sodium bicarbonate: Depleted uranium is found in reactor fuel rods and nuclear weapons. It can cause acute tubular necrosis (ATN) and renal failure in cases of internal contamination. The alkalinization provided by sodium bicarbonate makes the uranium less nephrotoxic. Administer an initial bolus of 2 mEq/kg intravenously. Then add 4 ampules to 1 L of D5W and titrated to a urinary pH of 6.5-7.5. (Urinary acidification has been proposed to enhance the elimination of strontium.)

Wound excision

Wound excision may be considered when the wound is contaminated with an isotope that has a very long half-life, such as plutonium.

References:

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• Federal Emergency Management Agency (FEMA): Hospital Emergency Department Management of Radiation and Other Hazardous Materials Accidents (HMA). 1994.
• Gusev I, Guskova AK, Mettler FA: Medical Management of Radiation Accidents. Boca Ratan, FL: CRC Press; 2001.
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