Course Toxic Exposures

Humans are exposed to radiation on a daily basis. Radiation is produced by natural and man-made sources. Eighty percent of daily human exposure occurs from natural resources such as sunlight (gamma radiation), radon gas (produced by the decaying of uranium in soil), and cosmic rays.

Common man-made and generally well-tolerated exposures occur in the form of microwaves, radiographs in hospitals, and televisions. Most radioactive exposures cannot be perceived by the human senses. Radioactive disasters can occur from leaks or damage to a nuclear power plant as in Japan after the 2011 earthquake and tsunami or nuclear or dirty bombs. A dirty bomb is a conventional explosive that is designed to release a radionuclide, usually containing low grade radioactive material. A possible radiation exposure, perhaps more than other exposure, may incite fear in the public. This may lead to extremely large numbers of the worried well, which can overwhelm a facilities capacity. It will be crucial to have proper and quick dissemination of information. For example, alpha particle radiation can be stopped by paper and is only harmful if internalized by ingestion, inhalation, or in a wound. It may be safer for the public to simply remain at home.

As previously mentioned in Section IV, slowly remove all the patient’s clothing and double bag it, 90% of decontamination can be accomplished by this step alone. Radioactive dust on clothing and skin can lead to further patient and healthcare personnel contamination. Carefully scrub all open wounds with soap and water in an effort to remove any radioactive dust that could lead to deeper contamination of the wound. Remove any foreign bodies, as these may be radioactive fragments. These are best deposited into a leaded container. All bodily fluids (urine, stool, vomit, etc.) are potentially contaminated in these patients and should be handled as toxic waste with proper disposal.

Specialty care is usually initiated at a hospital. Obtain a complete blood count (CBC) as soon as possible. Obtain CBCs three times a day for the following 2 to 3 days in order to follow the decline in lymphocytes. The rate of decline correlates fairly well with the degree of exposure. The Andrews nomogram can be used to predict the severity of exposure. Collect nasal and skin swabs along with urine and stool samples to identify external and internal contamination. Notify the local health department immediately if rescue workers have not already done so.

Exposed patients must have an individual radiation dose assessment calculated. Medical personnel must often rely on clinical features for clues to exposure amounts. Consult experts with any suspected extensive radiation exposure to provide accurate dose assessment. Whole body irradiation is equal to 1 gray (Gy). A gray is an International System unit that is equal to 100 rads (radiation absorbed dose). Box 6 lists the clinical clues to determine the extent of a patient’s exposure.

Higher radiation exposures have more rapid symptom onset and increased severity of symptoms. Acute radiation syndrome develops in 4 phases: prodrome, latent, manifestation of illness, and recovery. Patients with very high levels of radiation exposure may experience all of these phases within hours prior to their deaths. The physician can use the length of the latent phase to roughly estimate possible exposure amount. Time to vomiting may be an especially important diagnostic clue. Early, severe vomiting indicates a significant and possibly lethal radiation exposure. Table 6 shows a brief description of each phase.

As mentioned previously, the outcome for radiation exposure is directly related to the exposure magnitude suffered by the patient. Children are more susceptible to radiation and therefore require lower radiation doses than adults to develop each potential outcome. Table 7 shows the potential outcomes and the recommended therapies for radiation doses in adults.

Chelation may be indicated in specific scenarios. For example, Prussian blue has been used in cases of exposure to cesium-137.

Potassium Iodide Therapy

Radioiodines are common isotopes released from nuclear power plant reactions. The thyroid is targeted by radioiodines and exposure puts one at risk for future development of thyroid cancer. The younger victim naturally has a longer expected lifespan and consequently a longer time period in which the cancer can develop. Treat infants and children exposed to >0.05 Gy (5 rads) with potassium iodide (KI). KI will block thyroid uptake of radioiodines and help protect the thyroid from radioactive exposure. If given before the exposure, KI can prevent 100% of radioiodine uptake. If given after the exposure has occurred, the efficacy decreases quickly with time. If possible, give pediatric patients KI prior to or within 2 hours of exposure. If given 24 hours after exposure, the efficacy decreases to < 10 %. 1 shows KI dosing by age.

KI tablets can be dissolved in a pleasant tasting liquid, such as formula, milk, juice, or soda. Side effects are mild and include gastrointestinal distress and/or rash. One KI dose is effective for 24 hours. The halflife of KI is 5 hours to 7 days. Most patients require 1 dose. Once the exposure threat has passed, KI therapy will no longer be required. When removal from the exposure is impossible, subsequent doses will be required. Infants given 1 dose of KI should have their thyroid levels determined in 2 to 4 weeks. Those infants who were given multiple doses will require longer follow-up of their thyroid function.

Radioiodine is secreted into human milk. If possible, exposed lactating mothers should not breastfeed their infants. If breastfeeding is continued, then those infants will require additional KI doses and longer thyroid function follow-up. Radioiodine is also secreted into the milk of livestock and accumulates in local produce. Physicians should instruct their families to refrain from giving their children animal’s milk or local produce until public health authorities have deemed it safe to consume these products.

Other potential radiation treatments exist for specific radioactive elements: Prussian Blue (Radioactive cesium and thallium), Diethylenetriamine Pentaacetate or DTPA (Radioactive plutonium, americium, and curium), and filgastrim can be used to stimulate WBC growth in cases of bone marrow suppression.