Major Radiation (NEJM 346:20 May 16, 2002)
Best Recent Review (Annals EM 2005;45(6):643)
Radiogardase® – medical-grade Prussian blue was approved for these indications by the FDA in late 2003. In fact, the FDA solicited drug manufacturers to make and stockpile this drug in anticipation of nuclear exposure from a radiological dispersal device (RDD) or dirty bomb.
In the event of exposure to 137Cs or 201Tl, victims will take 500-milligram capsules either swallowed whole or mixed in liquid 3 or 4 times daily for up to 150 days. Unfortunately, taking the powder rather than the capsule leads to blue mouth and teeth as a side effect. No matter which way people take it, they will have blue stools. Remember that stools and urine are considered contaminated and must be disposed of appropriately. Prussian blue artists dye is not designed to treat radioactive contamination and is not manufactured to be taken internally.
The US government is stockpiling supplies of the following antidotes which will be distributed in the event of nuclear warfare:
- Prussian blue which blocks radioactive cesium and thallium
- Potassium iodide which blocks thyroid uptake of 131-iodine
- Calcium DTPA and zinc DTPA to treat exposure to plutonium, americium, curium, californium, and other transuranium elements (supplies are being solicited by the government)
- Sodium alginate (used in the food industry as a stabilizer, thickener, gelling agent, and emulsifier) to treat exposure to 90-strontium.
Types of Radiation
α (alpha) particles-positively charged particle consisting on 2 protons and 2 neutrons (a helium molecule without its electrons) Poor penetration, can be stopped by a sheet of paper. Dangerous only with internal contamination. High energy
γ (Gamma) ray-electromagnetic energy without mass. Reduced by nuclear decay. High tissue penetration.
Units of Measurement
Rad=radiation absorbed dose. Not a measure of biological effect
Rem=roentgen equivalent in man. Biological equivalent of
Roentgen=the ionization of air by X-Rays, useless for tissues
Radon: only emits alpha particles so must inhale actual material
Strontium: from nuclear fallout
Iodine: nuclear reactor accidents
Thorium: historically available as radiology contrast agent, thorotrast
Cesium: gamma emitter. Incident in Goiania, Brazil where medical emitter was stolen and sold to a junkyard. Junkyard owner and his kids thought this was great fun as it glowed in the dark. Severla folks died. Use Prussian blue.
Uranium: mainly daughter compounds that will get you
Radium: used for glow in the dark watch dials and fire detectors. Alpha emitter so low risk
In light of the events of September 11, 2002, the terrorist attack has moved to the forefront of emergency department (ED) and Emergency Medical Services (EMS) planning. One threat that must be considered is the use of radiologic weaponry. 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.
RECOGNITION OF CONTAMINATION
The first step of recognizing contamination is to understand the difference between exposure to and contamination by radiologic agents. Proximity to material emitting ionizing radiation defines exposure. Actually touching, breathing in, or swallowing that material is contamination.
A useful analogy is to imagine a person sitting around a campfire. By merely sitting next to the fire, the individual is exposed to the heat. If the person sits close enough to the fire, he or she might even get burned; however, as soon as the person is removed from the proximity of the fire, he or she would certainly not burn anyone else. If the person falls into the fire, in addition to being burned, he or she becomes covered in ash. This is external contamination. If other people touch the individual who fell into the fire, they would get ash on their hands, spreading the contamination. In the course of falling into the fire, if the individual swallowed, breathed in, or absorbed any of the ashes through cut skin, he or she would be internally contaminated as well.
PERSONAL PROTECTIVE EQUIPMENT
For an isolated radiologic incident, level D personal protective equipment (PPE) is all that is required. Level D PPE consists of surgical gown, mask, and latex gloves (universal precautions). If airborne contamination is a possibility, the use of a fitted air-purifying respirator (N95 or 100 filter mask) increases protection. Eye protection should also be worn to prevent ocular contamination from any splashing during the decontamination procedure. If any possibility of mixed exposure exists, higher levels of PPE may be required as dictated by the chemical or biological agents involved (see CBRNE – Personal Protective Equipment). Local and state laws, facility protocols, and Occupational Safety and Health Administration (OSHA) regulations must be followed.
The use of shielding devices that are normally used for radiology studies are not recommended for radiologic decontamination. These devices, such as lead aprons, were designed to block low-energy radionuclides and are not effective shields for the high-energy emissions present in most decontamination encounters. In addition, their bulk hinders the decontamination process and therefore leads to an increased time of exposure.
As noted above, shielding capacity is limited in the hospital environment. Other factors, however, may potentially limit exposure to those providing patient decontamination. These are time, distance and quantity. The longer the time spent in the contaminated environment, the greater the dose of radiation to the worker, so a rotating team approach is advised. Doubling the distance from the radioactive source decreases the dose by a factor of four. Likewise, limiting the quantity of radioactive items in the decontamination area is advisable.
The process of external decontamination can be divided into 2 stages: gross and secondary decontamination.
Gross decontamination is usually performed before the patient reaches a hospital environment. It consists of removal of all the patients clothing and, if possible, brief irrigation of the patients entire body with water. Clothing should be removed with a careful “roll-down” method to prevent inhalation of airborne particulates. If the patient is contaminated solely by a radiologic source, water is sufficient for the washing. If a possibility of mixed contamination exists, the protocols for biologic and/or chemical decontamination should be used because these regimens are more extensive than those used for radiologic decontamination. Since most radiologic contamination is located on the head and hands, initial showering should be carried out with the patient in the “head-back” position to prevent run-off into the eyes, nasal or oral cavities. Early handwashing is also important
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 most centers, the decontamination site is outside and immediately adjacent to the ED. The small amount of radioactivity present in the irrigation runoff produces minimal risk to the communal water supply or groundwater and, therefore, patient decontamination should not be delayed by attempts to contain run-off. However, facility protocols and local, state and federal laws should always be followed. After gross decontamination, the patient should be wrapped in a sheet for transport into the ED.
If the patient requiring decontamination becomes medically unstable at any point during the process, provision of medical care should take precedence over decontamination. The risk to care providers when treating a patient with radiologic contamination is virtually nil. If available, a radiation survey meter can be used to identify the extremely rare case of a patient who is emitting a sufficient amount of radiation.
In the event of a mass casualty incident, gross decontamination is all that is immediately necessary. Patients should disrobe, with assistance if necessary. If able to ambulate, patients can briefly shower in a decontamination area. Likewise, the decontamination team needs only water to briefly wash patients who are unable to shower themselves. At this point, patients are sufficiently decontaminated and can receive treatment of any medical problems. Secondary decontamination in these patients can be performed later when more resources are available.
Secondary decontamination is a stepwise methodical cleansing of any remaining radioactive areas of the patient. It should be performed under the guidance of the hospitals Radiation Safety Officer (RSO) or another member of the team trained in the use of radiation detection devices (RDD), such as a radiac instrument.
An area in the ED should be set aside for the decontamination procedure. Because this area may be out of service for a significant period, a location should be chosen that will not interrupt the normal workings of the department. A path to the decontamination room should be made with paper floor coverings and clear barriers to prevent the spread of contamination. In addition, these barriers prevent the entrance of extraneous personnel and visitors.
A decontamination team customarily consists of the RSO, and two assistants, one of whom may be a clinician. In a mass-casualty setting, however, clinicians will likely not be available to perform decontamination. All members of the team should change out of their normal clothing into attire that can be bagged after the procedure. Shoe coverings, surgical masks, and eye protection should also be worn. Each member should be issued a dosimeter, which is a device that passively measures exposure to radioisotopes.
The general procedure for secondary decontamination involves using a RDD to perform a head-to-toe survey of all areas of the patients body. Further irrigation is required for any areas with readings above the threshold, which is determined by the radiation safety officer on the basis of RDD calibration. 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. These levels may be slightly above baseline and should be determined by the RSO and treating physicians.
Certain areas of the body require special procedures, as follows:
- Mouth: Remove and bag any false teeth, loose dental work, or foreign bodies. Take swab samples from the oral cavity. Preferable sites for swabs are under the tongue and between gums and teeth. The patient or physician should gently brush the teeth, gums, and tongue, being careful to avoid irritating the gums and causing bleeding. The mouth should then be copiously rinsed, taking care to avoid swallowing the rinse water. Resample with the RDD as above.
- Nose: Obtain nasal swabs. The patient should then gently blow his or her nose. Irrigate the nares while the patient leans forward, taking care to prevent the irrigating solution from being swallowed or aspirated.
- Eyes: If no contraindications exist, anesthetize the eyes with a topical agent. Sample the conjunctiva with moistened swabs, and irrigate copiously with saline. This can be facilitated with commercial eye irrigation devices, or a nasal canula attached to an intravenous (IV) bag can be used as an improvised eye irrigation system. If irrigating manually, irrigate medial to lateral with the patients head turned to side to minimize contamination of the lacrimal duct.
- Ears: Take samples from external canal with moistened swabs. Examine the tympanic membrane for perforation, especially after blast incidents. If no perforation is found, copiously irrigate the canals with saline warmed to body temperature.
- Open wounds: Obtain wound swabs. If any particulate matter or foreign bodies are present, they should be removed and saved. Copiously irrigate the area and resurvey as in intact skin. Cover the wound with waterproof dressing to avoid recontamination from the run-off from irrigating other areas.
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 and are very difficult to remove. Therefore, EDs that are expected to care for these contaminated 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. No studies using gastric lavage or emetic agents for radiologic decontamination have been performed. However, a comparison can possibly be made with toxicologic exposures in which there are few recommended uses for these procedures. The authors currently do not recommend the routine use of gastric lavage or emetic agents.
There are particular enteral binding methods that have been known to work for specific agents of contamination.
Barium sulfate: This medication, which is used most extensively for radiology contrast studies, forms irreversible bonds with strontium, which is a breakdown product of uranium, and radium, which is used in older military, industrial, and medical equipment. Once bound, these agents pass through the gastrointestinal tract unabsorbed.
Aluminum and magnesium salts: Commercially available in agents such as Maalox and Mylanta, these salts bind to and reduce the absorption of strontium, radium, and phosphorus similar to barium sulfate.
Prussian blue: This agent binds to and increases the elimination of cesium, which is found in medical radiotherapy devices and was used by terrorists in Russia during an attempted attack, and thallium, which is used in medical imaging. It also blocks the absorption of rubidium. If internal contamination with one of these agents is present, contact the Radiation Emergency Assistance Center/Training Site (REAC/TS) as soon as possible (see Obtaining Expert Advice). The Oak Ridge Institute of Science and Education, which is the parent organization of REAC/TS, has given Prussian blue investigational new drug (IND) status for use in the United States. It is available to the civilian medical community overseas.
Activated charcoal: In a patient without a decreased level of consciousness, the administration of one dose of activated charcoal may bind to and speed the elimination of some radioisotopes. Because the adverse effects of this medication are rare, activated charcoal is recommended if administered shortly after exposure.
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. Competitive blockade of RAI and technetium uptake can be achieved with large doses of KI. 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.
Calcium: Calcium gluconate or calcium chloride can be administered to limit the incorporation of strontium or radioactive calcium into bone.
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.
Phosphorus: Similar to dilution of tritium, oral loading with phosphorus salts (Neutra Phos) can enhance the elimination of radioactive phosphorus.
Diethylenetriamine pentaacetic acid (DTPA): Americium (a daughter product of plutonium found in nuclear weapons), uranium, plutonium, and other heavy metals (present in nuclear reactors and weapons) are very poorly excreted by the kidneys. Calcium (Ca)DTPA and zinc (Zn)DTPA form compounds with the above radioisotopes and other transuranium metals and rare earths rendering them more easily excreted by the kidneys, enhancing elimination. The Oak Ridge Institute of Science and Education has given DTPA IND status. Contact REAC/TS as soon as possible in the event of contamination (see Obtaining Expert Advice).
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.
In 2003, Prussian blue (ferric hexacyanoferrate) became the first FDA approved treatment for radioactive and
non-radioactive cesium and thallium exposures. It is a synthetic pigment that has been used in art and printing
since 1704 and is named Prussian blue because it was once used to dye Prussian military uniforms. It
has a crystal lattice structure that attracts and traps monovalent alkali metals in the GI tract. Once bound, the
elements cannot be reabsorbed into the bloodstream, so they are passed out of the body in the stool. Although
Prussian blue prevents the absorption of cesium and thallium, it cannot treat the complications associated
with these agents once they occur. If a patient develops complications of cesium or thallium toxicity,
such as neuropathy, destruction of bone marrow, neutropenia and thrombocytopenia, supportive treatment
should be given in addition to Prussian blue.
Radiogardase, the brand name of Prussian blue, is available as 0.5g capsules. The usual dose for cesium and
thallium exposures is 3g orally three times a day for an adult and 1g orally three times a day for a child. Higher
doses have been recommended by some for thallium poisoning. The duration of therapy for cesium toxicity is
a minimum of 30 days; duration for thallium is unclear. The capsules can be swallowed whole, or the contents
of the capsules can be dissolved in a liquid or sprinkled onto bland food. Because Prussian blue often causes
constipation, the capsule contents may be dissolved in 50ml of 15% mannitol or taken with a high fiber diet.
Like thallium and cesium, potassium in the GI tract is also bound to Prussian blue. This can lead to hypokalemia,
which is why caution should be taken when giving Prussian blue to patients with electrolyte imbalances
or cardiac arrhythmias. Prussian blue is also known to cause blue stools, as well as blue mouth,
tongue, and teeth if the powder is removed from the capsule prior to administration.
Prussian blue is included in the CDC Strategic National Stockpile due to the concern that cesium could be
used as a component in an explosive device (dirty bomb). The only commercial distributer of Prussian blue in
the US is Heyltex Corporation of Katy, Texas, 281-395-7040 or
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. (Urinary acidification has been proposed to enhance the elimination of strontium).
Wound excision may be considered when the wound is contaminated with an isotope with a very long half-life such as plutonium.
OBTAINING EXPERT ADVICE
The treatment of patients with internal contamination involves complicated diagnostic and therapy regimens. In addition to the local poison center (nationwide number 1-800-222-1222), one of the following agencies should be contacted for guidance as soon as possible.
- Armed Forces Radiobiology Research Institute (AFRRI) – Web site, http://www.afrri.usuhs.mil/; telephone, (301) 295-0530[Phone# verified 11/07/02]
- Radiation Emergency Assistance Center/Training Site (REAC/TS) – Web site, http://www.orau.gov/reacts/; telephone, (865) 576-1005 (ask for REAC/TS)
- Arnold JL, Lavonas E: CBRNE – Personal Protective Equipment . eMedicine Journal [serial online]. 2001 Available at: http://www.emedicine.com/emerg/topic894.htm.
- Dill C, Hoffman RS: Radiation Emergencies. Resident & Staff Physician 2002; 48: 24-33.
- Federal Emergency Management Agency (FEMA): Hospital Emergency Department-Management of Radiation and Other Hazardous Material Accidents (HMA). 1994.
- Gusev I, Guskova AK, Mettler FA: Medical Management of Radiation Accidents. Boca Ratan, FL: CRC Press, 2001.
- Jarret D: Medical Management of Radiological Casualties Handbook. Bethesda, MD: Armed Forces Radiobiology Research Institute; 1999.
- Mettler FA, Upton AC: Medical Effects of Ionizing Radiation. Philadelphia: WB Saunders; 1995.
- National Council on Radiation Protection and Measurements: Management of Persons Accidentally Contaminated With Radionuclides. Bethesda, MD: National Council on Radiation Protection and Measurements; 1993.
- Radiation Emergency Assistance Center/Training Site (REAC/TS): Guidance for Radiation Accident Management . Available at: http://www.orau.gov/reacts/manage.htm.
- Reed W: Medical Effects of Ionizing Radiation Course. Washington, DC: Armed Forces Radiobiology Research Institute; January 7-9, 2002.
Review Article (NEJM 346:20, May 16, 2002)