Treatment of Radiological Casualties: Update of Current Concepts

Katan Patel

Disclosures

AccessMedicine from McGraw-Hill 

With the increasing threat of nuclear and radiologic terrorism, physicians need to be familiar with the basics of treatment should such an incident occur. Koenig et al.[1] review current guidelines for medical treatment of radiologic casualties and, also, discuss more recent advances. It is important to note the distinction between a nuclear versus a radiologic weapon. A radiological weapon is any device that is designed to spread radioactive material into the environment. Usually, high explosives are used to disperse the radioactive material. Hence, the term "dirty bomb." A nuclear bomb, however, involves the splitting of atoms to produce the tremendous force and destruction of a nuclear blast with a much higher amount of radioactive fallout.

Casualties who receive a radiation dose between 2 and 6 Gy are the most amenable to treatment. Those who are exposed to greater than 4 Gy will usually die within 30 days without treatment. Tissues that are most sensitive to radiation include the GI tract and bone marrow as these are made up of rapidly dividing cells.

For whole-body radiation exposure, such as from a nuclear or radiologic bomb, time to emesis post-event is a useful tool to screen those patients who require prompt medical attention. (See Table 1 .)

Further, serial CBC's indicating a significant decrease in lymphocytes in the first 6 to 48 hours identify those patients who will need more prolonged medical treatment. (See Table 2 .)

The level of exposure can usually be predicted based on the severity and type of symptoms. If there is immediate nausea and vomiting, prostration, hypotension, ataxia, and convulsions (CV/CNS Syndrome), the patient most likely received doses greater than 30 Gy. These patients usually undergo palliative care as death inevitably occurs within days. Exposure to this high a dose, however, is extremely rare. If there is sudden onset of nausea and vomiting and diarrhea followed by a latent period of 1 week, and then a more severe decline (GI syndrome), the patient most likely was exposed to a dose of 6 to 20 Gy. If there is a latent period of 2-3 weeks, followed by pancytopenia and concurrent hemorrhage and infection (hematopoietic syndrome), then the patient most likely received a dose of 2 to 10 Gy.

A thorough medical history is absolutely essential in the workup of a radiologic casualty. If the patient is aware, the physician must inquire about the radiation source as well as time to onset and severity of symptoms. A CBC with differential should be ordered upon presentation and every 4 to 6 hours thereafter to observe any drops in lymphocyte count.

Localized radiation exposure, as opposed to whole-body radiation, occurs after direct handling of radiologic materials. This usually entails local thermal injury rather than systemic manifestations. Such exposure usually presents with erythema and blistering, which occurs 12-20 days post-event. Immediate treatment includes pain control, prevention of infection, and vasodilators. Ultimately, the patient may require surgical treatment.

Medical treatment is only necessary for those patients who were exposed to a dose greater than 1 Gy. Antibiotics are generally not needed during the first week post-exposure. After that time, anti-bacterial, anti-viral, and anti-fungal agents can be used to combat opportunistic infections.

After the primary assessment (ABC's) and medical/surgical stabilization, the physician should aim to prevent/minimize internal contamination. This is done by first removing the outer clothing and shoes and then washing the skin and hair gently with soap. Such actions will significantly decrease the level of external contamination and hence reduce the risk of more life threatening internal exposure. Further, one can use a radiation detector to look for residual levels of contamination. Contaminated wounds pose a serious threat to internal exposure via access of radiologic particles through vasculature. Treatment of these wounds is more complex and depends on the extent of damage. Abrasions should be cleaned as described above. Lacerations should be irrigated first. However, if this is not sufficient, tissue excision should be considered. Puncture wounds are difficult to manage since radiation exposure is generally very deep. If the patient has ingested any radioactive material, the first step should be administration of antacids such as aluminum hydroxide or magnesium carbonate. However, within 2 hours post-ingestion, gastric lavage and/or cathartics may be considered, depending on the amount ingested.

Actual medical countermeasures fall into three broad categories:

  1. Radioprotectants are drugs that serve a prophylactic function by preventing cellular and molecular damage. Amifostine was one of the first drugs approved as a radioprotectant. It is traditionally given to reduce dry mouth prior to receiving radiotherapy in patients with head and neck cancer. However, in the event of a nuclear or radiologic disaster, amifostine can be potentially used by first-responders as a prophylactic agent to decrease the effective radiation dose. However, due to dose-limiting effects, toxicity, and IV administration, experience with this drug is limited. Further, it has no role for patients who have already been exposed to radiation.

  2. Radiation mitigators are agents that speed up recovery or repair after radiation injury. Colony stimulating factors such as filgrastim and sargramostim, traditionally used for chemotherapy, are currently under investigation for use in patients with severe neutropenia post-radiation exposure. Studies have shown that these drugs significantly shorten the duration of the neutropenia after exposure. One study mentioned in the review suggest initiating filgrastim at 5 ug/kg/day as soon as possible after exposure and continuing treatment until neutrophil counts are above 1000. Patients who do not respond to bone marrow stimulation with drugs may be considered for bone marrow transplantation. However, experience with transplantation for treatment of radiation injury is limited.

  3. Radionuclide eliminators are drugs that block absorption of radioactive iodine particles that have already been internalized. Potassium iodide can be used to block thyroid uptake of radioactive particles. However this does not protect from external radiation and must be given within a few hours post-exposure. This drug serves more of a use in the pediatric population since children are more vulnerable to the effects of radio-iodines than adults. Prussian blue (ferric hexacyanoferrate) is another eliminator that hastens fecal elimination of cesium and thallium. These isotopes are ideal agents that can be used by terrorists as a radiological weapon. In such an event, the physician should consult with a health physicist to determine if the annual limit of intake has been surpassed, in which case treatment is usually initiated. Other eliminators such as Ca-DPTA and Zn DTPA can be used as chelating agents that form a complex with the radioactive particles and are then eliminated in the urine. The FDA recommends an IV loading dose of 1.0g in adults and 14 mg/kg in children as soon as possible post-exposure. A similar maintenance dose should be given once a day. The duration would depend on the actual level of contamination. In pregnant women, Zn-DTPA should be used.

Medical stabilization should always take precedence. However, one must also consider long term psychological effects such as post-traumatic stress disorder in the event of a radiologic casualty. Mental health professionals should be consulted and patients should have good follow-up care. Persons at greatest risk include those directly exposed to radiation as well as patients with a history of mental illness.

The lack of experience in nuclear or radiological disasters raises many health policy questions. Healthcare facilities should implement adequate evacuation plans, develop clear communication systems, stockpile medical countermeasures, and discuss triage plans and procedures. Emergency departments should consider storing Geiger-Muller equipment to assess external contamination and should also develop specific protocols to deal with persons exposed to radioactive materials along with plans to refer patients to more specialized facilities if needed.

With the ongoing threat of a terrorist attack using nuclear or radiological weapons, emergency physicians should be better prepared should such an event ever occur. Emergency physicians should always first address traumatic and medical emergencies before assessing radiation damage. A thorough history and physical exam is critical with emphasis on identifying the source and timing of exposure and time to onset of symptoms. Serial CBC's should be obtained to monitor lymphocyte decline. Most external contamination can be reduced by removing outer clothing and gently washing the skin with soap and water. Medical countermeasures can be implemented depending on the individual hospital's protocol and stockpile. Potassium iodide should be given only if there is confirmed radioiodine exposure. The physician should also consult with a health physicist to determine a more exact assessment of radiation exposure.

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