eMedicine Specialties > Emergency Medicine > Warfare - Chemical, Biological, Radiological, Nuclear and Explosives
Author: Scott D Weingart, MD, Assistant Clinical Professor and Director, Division of Emergency Department Critical Care, Department of Emergency Medicine, Mount Sinai School of Medicine
Coauthor(s): Ben R Maltz, MD, State Surgeon, Washington Army National Guard, Science Officer, 10th Civil Support Team (Weapons of Mass Destruction)
Updated: Mar 9, 2009
In light of the events of September 11, 2002, 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 completed, rapid decontamination can reduce morbidity and mortality, limit the spread of contamination, and keep the ED functioning for the treatment of other patients.
For related information, see CBRNE - Radiation Emergencies. For excellent patient education resources, visit eMedicine's Bioterrorism and Warfare Center. Also, see eMedicine's patient education article Chemical Warfare.
Recognition of Contamination
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.1
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, inhaled, 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.2,3
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 situations. In addition, their bulk hinders the decontamination process and therefore leads to an increased exposure time.
Shielding capacity is limited in the hospital environment. However, other factors may potentially limit exposure to those providing patient decontamination. These factors are time, distance, and quantity.
The longer the time spent in the contaminated environment, the greater the dose of radiation to the worker; therefore, a rotating team approach is advised. Doubling the distance from the radioactive source decreases the dose by a factor of 4. Likewise, limiting the quantity of radioactive items in the decontamination area is advisable.
External Decontamination
The process of external decontamination can be divided into 2 stages: gross decontamination and secondary decontamination.
Gross decontamination
Gross decontamination is usually performed before the patient reaches a hospital environment. It consists of removal of all the patient's clothing and, if possible, brief irrigation of the patient's 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, the patient should be in the "head-back" position during initial showering to prevent run-off into the eyes, nose, or mouth. Early handwashing is also important.
Gross decontamination removes more than 95% of external contamination and renders the patient safe for access by care providers.1 If gross decontamination has not occurred in the field, it must be performed by ED personnel in a designated decontamination site. 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; 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 an amount of radiation sufficient to cause concern.
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 of these patients can be postponed until more resources are available.
Secondary decontamination
Secondary decontamination is a stepwise methodical cleansing of any remaining radioactive areas of the patient. It should be performed under the guidance of the hospital's 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 would 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. However, in a mass-casualty setting, 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 an RDD to perform a head-to-toe survey of all areas of the patient's body. Further irrigation is required for any areas with readings above the threshold, which is determined by the RSO on the basis of the 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. Acceptable 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:2
* Mouth: Remove and bag any dentures, 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 copiously irrigate 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 patient's head turned to the side to minimize contamination of the lacrimal duct.
* Ears: Take samples from the external canals with moistened swabs. Examine the tympanic membranes 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
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. 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.
Enteral binding methods: Some enteral binding methods have been shown to effectively bind specific agents of contamination.4,2
* Barium sulfate: This drug, which is commonly used for radiographic contrast studies, forms irreversible bonds with strontium and radium, which are used in older military, industrial, and medical equipment. Once bound, these agents pass through the gastrointestinal tract unabsorbed. A 1-time dose of 200 mL of 100% barium sulfate should be administered for internal decontamination.
* 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 in a manner similar to barium sulfate. A dose of 100 mL of either of these agents should be given by mouth or nasogastric tube as soon as possible after exposure.
* Prussian blue: This agent binds to and increases the elimination of cesium and thallium. Cesium is found in medical radiotherapy devices and was used by terrorists in Russia during an attempted attack; thallium is used in medical imaging. Prussian blue also blocks the absorption of rubidium. If internal contamination with one of these agents is present, administer 1 g by mouth tid for 3 weeks. This medication has recently received FDA approval under the name Radiogardase.
* Activated charcoal: In patients 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. A dose of 50-100 g should be given by mouth or gastric tube; if the patient is at risk for aspiration, this medication should be avoided.
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. 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 intravenous 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 Neutra 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. These drugs were recently FDA approved. The Oak Ridge Institute of Science and Education has given DTPA IND status. Immediately contact REAC/TS in the event of a contamination (see Obtaining Expert Advice).
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.
Obtaining Expert Advice
The treatment of patients with internal contamination involves complicated diagnostic and therapeutic 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; telephone, (301) 295-0530
* Radiation Emergency Assistance Center/Training Site (REAC/TS) Web site; telephone, (865) 576-1005 (ask for REAC/TS)
No comments:
Post a Comment