Toxicology, Disaster Medicine, Trauma

So I Watched CHERNOBYL… Now What? Revisiting Acute Radiation Syndrome

Although more than 119 million U.S. residents live within 50 miles of a nuclear power plant, most emergency physicians are unfamiliar with management of radiation-related injuries, including mass casualty from nuclear accidents.1

Military attacks or natural disasters affecting civilian nuclear power plants are extremely unlikely. However, physicians ought to be prepared to care for the more plausible patient injured from working in an industrial, military, research, or medical setting with known radiation risks. Alternatively, cases of radiation sickness have occurred as a result of patients unwittingly handling discarded radiation sources.2

Pathophysiology of the Effects of Radiation
Radiation injury is caused by deposition of energy in tissues, which promotes free radicals and disruption of DNA and other cellular structures. Radiation exposure can occur through inhalation, ingestion, and transdermal absorption.3 However, body parts and tissues are not affected equally. Rapidly proliferating cell lines such as intestinal mucosa and bone marrow are most immediately sensitive to radiation and manifest the symptoms of Acute Radiation Syndrome. Exposure to less than 1 Gy (1 Gy = 100 rads) is unlikely to produce symptoms, whereas greater than 10 Gy is fatal. Exposure to radiation over time increases the risk of eventual malignant transformation.4

Progression of Illness
The prodromal phase of acute radiation sickness occurs within minutes to days of exposure to at least 1 Gy. During the latent phase, symptoms appear to improve or abate for several days to a month. The manifest phase lasts from hours to months and features the most severe symptoms.3 Increasing doses of radiation leads to acceleration of the timeline such that exposure to higher levels of radiation can lead to immediate prodromal symptoms as well as progression to the manifest phase within hours to days. This accelerated sequence is almost uniformly fatal.

Management
CONSULT SPECIALISTS

As soon as possible, recruit the help of your designated hospital radiation safety officer and toxicologist.

The Radiological Assistance Program of the U.S. Radiation Emergency Medical Management (REMM) has a 24-hour hotline available at 202-586-8100, which offers specialized assistance and reporting.

The U.S. Department of Energy Radiation Emergency Assistance Center/Training Site (REAC/TS) is also available to assist 24/7 at 865-576-1005.

Colleagues from radiology, hematology-oncology, trauma surgery, and burn centers may provide additional expertise in these cases.

DECONTAMINATION
Personal protection equipment should include disposable scrubs with taped seams, shoe covers, hats, masks, and goggles. Staff should wear a personal dosimeter to monitor exposure. The goal of decontamination is to reduce the level of contamination to twice the level of background radiation or until subsequent attempts fail to reduce the level of contamination by less than 10%, or according to consultant guidance.4 Removal of clothing should reduce the level of external contamination by 90%.7 Residual radiation contamination is then evaluated by passing a Geiger counter at a constant distance from the skin over the entire body. Residual contamination is then removed by gently cleaning the skin and hair with soap and warm water to avoid damaging the skin.

Cover any open wounds to prevent further contamination via runoff. Irrigate abrasions and puncture wounds with saline. Lacerations may require excision if standard irrigation is ineffective. Wounds containing impacted radioactive shrapnel require special care in order to avoid healthcare staff exposure. At times, amputation may be required to adequately remove the source of radiation from the penetrating wound.4,6

BIODOSIMETRY
A detailed history, including the source of radiation, the distance from the source, and how the patient was exposed, is critical to determine the course of treatment. Time to onset of symptoms can help estimate the exposed dose of radiation. Severity of exposure can be estimated based upon time to emesis; survival is inversely related to radiation dose. Emesis that occurs greater than 4 hours after exposure typically predicts a more mild course of sequelae. Emesis within 2 hours predicts at least 3 Gy dose of radiation. Clinicians typically closely follow the absolute lymphocyte count, since it predictably correlates with the amount of exposure to radiation in a dose-dependent manner. Though less frequently used in clinical practice, the gold standard for biodosimetry is the lymphocyte chromosomal dicentrics assay. The assay requires a culture of 48-72 hours to yield results and may be ordered through the Radiation Emergency Assistance Center/Training Site.8,9,10 The REMM App has useful decision tools for quickly estimating exposure of radiation based upon time to emesis, lymphocyte kinetics, and chromosomal dicentrics assay.

Treatment
Manage ABCs first. Treatment of life-threatening conditions has priority over treatment of radiation-related injuries.11 As soon as possible, obtain baseline CBC with differential and platelet count and repeat every 2-3 hours for the first 48 hours to continue to monitor for declines in lymphocytes. Obtain type and screen for HLA typing, in case transfusions are required. Obtain routine urinalysis and basic metabolic panel to determine baseline renal function. Swab body orifices to determine whether internal exposure has occurred. Collect 24 hour sample of urine for 4 days for radionuclide identification.12

Supportive care and resuscitation should include antidiarrheals, fluids, electrolytes, non-NSAID analgesics, and burn care. Radiation experts may recommend cathartics, gastric lavage, and activated charcoal if ingestion is suspected. Any surgical intervention should occur within 36 hours of exposure.3,14,12

Any blood products administered should be leukoreduced and irradiated. Internal contamination treatment is determined by the specific radionuclide contaminant. For instance, if the patient was exposed to radioiodines, potassium iodide should be administered within 4-6 hours of exposure.3 If estimated exposure is greater than 2 Gy, consider human leukocyte antigen testing in anticipation of future pancytopenia management. Consult radiation experts and hematology to determine if granulocyte colony stimulating factor is indicated and the recommended regimen.12

Take-Home Points
● Radiation injury promotes free radicals and disruption of DNA and other cellular structures
● Rapidly proliferating cell lines such as intestinal mucosa and bone marrow are most immediately sensitive to radiation
● Recruit help as soon as possible from local and national institutions, including your toxicology service, radiation safety officer, REMM and REAC/TS.
● Decontaminate
● Download the REMM app to estimate the amount of radiation exposure
● Important diagnostic tests are CBC with differential repeated every 2-3 hours for the first 48 hours to continue to monitor for declines in lymphocytes, type and screen, urinalysis and basic metabolic panel
● Treat with supportive and symptomatic care including antidiarrheals, IVF, replete electrolytes, non-NSAID analgesics, and burn care
● If blood products are administered, they should be leukoreduced and irradiated.


References
1. Dedman B. Nuclear neighbors: Population rises near US reactors. NBCNews.com. http://www.nbcnews.com/id/42555888/ns/us_news-life/t/nuclear-neighbors-population-rises-near-us-reactors/#.XRQCVhNKjMJ. Published April 14, 2011.
2. Turai I, Veress K, Günalp B, Souchkevitch G. Medical response to radiation incidents and radionuclear threats. BMJ. 2004;328(7439):568-572.
3. Waselenko JK, Macvittie TJ, Blakely WF, et al. Medical management of the acute radiation syndrome: recommendations of the Strategic National Stockpile Radiation Working Group. Ann Intern Med. 2004;140(12):1037-1051.
4. Koenig KL, Goans RE, Hatchett RJ, et al. Medical treatment of radiological casualties: current concepts. Ann Emerg Med. 2005;45(6):643-652.
5. López M, Martín M. Medical management of the acute radiation syndrome. Rep Pract Oncol Radiother. 2011;16(4):138-146.
6. Radiation Emergency Medical Management. Procedures for Radiation Decontamination. https://www.remm.nlm.gov/ext_contamination.htm.
7. Mettler FA, Voelz GL. Major radiation exposure—what to expect and how to respond. N Engl J Med. 2002;346(20):1554-1561.
8. Radiation Emergency Medical Management. Dose Estimator for Exposure: 3 Biodosimetry Tools. https://www.remm.nlm.gov/ars_wbd.htm.
9. Oak Ridge Institute for Science and Education. Cytogenetic Biodosimetry Laboratory. https://orise.orau.gov/reacts/cytogenetic-biodosimetry-laboratory.html.
10. Centers for Disease Control and Prevention. Acute Radiation Syndrome: A Fact Sheet for Physicians. https://www.cdc.gov/nceh/radiation/emergencies/arsphysicianfactsheet.htm.
11. Smith JM, Ansari A, Harper FT. Hospital management of mass radiological casualties: reassessing exposures from contaminated victims of an exploded radiological dispersal device. Health Phys. 2005;89(5):513-520.
12. Lopez AM, Stephani JA. Radiation Injuries. In: Tintinalli JE, Stapczynski J, Ma O, Yealy DM, Meckler GD, Cline DM, eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide. 8th ed. New York, NY: McGraw-Hill; 2016. http://accessmedicine.mhmedical.com/content.aspx?bookid=1658&sectionid=109426307.

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