You are working in your quiet community ER when the disaster sirens sound off. You quickly turn on the TV to find that there has been an accident at the nuclear power plant. Your notification phone rings and there are reports of multiple causalities en route to your ED. You activate your local disaster response algorithm and get ready for some radiation injuries.

Physics for ER docs:

SI unit: 1 Gray (gy) = 1 joule/kg of matter absorbed (also known as 100 rad for old people)

SI unit: 1 Sievert (SV) = the amount of energy equal to 1 joule/kg to an effective dose of a joule of recipient mass (also known as 100 rem for old people).

Types of radiation

Alpha radiation: It is a particle and consists of two protons and two neutrons making it the heaviest form of radiation. Therefore, it is not very penetrating and very low range. More important clinically, alpha radiation does not cause any external harm to the body even if it is on the skin. However, if alpha particles are internalized either through inhalation or ingestion there is a large potential for harm.

Beta radiation: It is a particle and consists of electrons and positrons. Beta radiation has low mass and is fast moving. Therefore beta radiation has a large range and can penetrate deeper through the skin. Generally, injury from beta radiation is confined to the skin in the form of burns. Beta radiation is susceptible to shielding can be often blocked by a few inches metal.

Gamma Radiation: Is a photon and passes through matter easily. Generally very ionizing and causes lots of cell damage. Heavy exposure to gamma rays causes multi organ damage.

Overview of Acute Radiation Syndrome

Radiation Injury timeline

Prodromal Phase: Depending on the dose symptoms generally start minutes to hours after exposure. Usually symptoms are related to the GI or neuromuscular systems. GI symptoms generally include nausea, vomiting, diarrhea, GI upset and neuromuscular symptoms are generally fever, malaise, fatigue, hypotension, apathy. Though not a specific indicator, vomiting within 2 hrs of radiation exposure is a sign of possible high level radiation exposure. Latent Phase: A period where there is generally no symptoms. This period lasts 2-3 weeks in lower radiation exposures and is significantly shortened or eliminated completely with high dose radiation exposure. Illness Phase: Symptomatic phase, characterized by organ dysfunction due to cellular damage caused by radiation exposure. Recover/Death: Follows illness phase can be complicated with radiation side effects such as fibrosis, cardiomegaly, nephropathy and cognitive decline. Radiation effects by organ system Acute Hematopoietic Syndrome: A direct result of radiation damage to bone marrow. Encountered when dose is more than 2 gray and is associated with the 4 different phases. Length of the latent phase depends on the amount of radiation exposed and corresponds to the decline of blood cell counts. Erythrocytes are the most resistant to radiation damage while lymphocytes are extremely sensitive and undergo rapid apoptosis once exposed. Other blood cells decrease depending on the amount of damage to their progenitor cells and their overall half-life in the body. Acute Gastrointestinal Syndrome: Results from radiation damage to the GI system. Contains four phases. Prodromal phase is also associated with nausea and vomiting and the latent phase is variable. Radiation destroys the epithelial stem cells and denudes the endothelial lining of the GI tract. Generally occurs with radiation exposures greater than 7 gray. Illness is characterized by nausea, vomiting, bloody diarrhea, malabsorption, electrolytes imbalance, and illeus. Acute Neurovascular Syndrome: Caused by a large dose of radiation 20-30 gray. Contains a prodromal phase however occurs minutes after exposure and associated with disorientation and confusion. There is a short latent phase and is followed by a severe illness phase associated with ataxia, seizures, cardiovascular collapse, and coma. Inevitably all patients who presenting with neuromuscular syndrome die. Cutaneous Symptoms: Effects of radiation on skin are dose, depth, volume dependent. 5 Gy or higher will experience transient skin reactions, erythema, edema itching and tingling within 24 hrs of exposure. Prodromal period is usually 2-3 weeks and latent period is dependent on dosage. This period is then followed by progression of erythema to hyper-pigmentation, and dry to wet desquamation depending on dosage. At even high doses of >50 Gy, there may not be a latency period and progression from erythema to necrosis can occur in days. Clinical prognostication: In the event of a mass radiation exposure or even a single radiation exposure event it is important to estimate the amount of radiation received. This gives the clinician the expected prognosis and can help in resource management and tailoring of care to patients.

Currently, there is no emergent way to determine the dose of radiation an individual has been exposed to in the ED. The gold standard for determining survivability after radiation exposure is the absolute lymphocyte count within 8 hours of exposure. This test though very useful for inpatient management of acute radiation exposure may provide little information to the ED physician.

Onset of first emesis may provide a quick but inaccurate estimate of total radiation exposures. Patients vomiting >2 hrs or longer after exposure generally have a good prognosis and have likely been exposed to 2 Gy or less of radiation. Furthermore many of these patients are likely to be discharged. Vomiting between 1-2 hours post exposure signifies a moderate dose exposure 2-4 Gy and generally patients are observed. Vomiting within 1 hour of exposure is a sign of large radiation dosage. These patients should be admitted and if possible transferred to a specialized treatment center. Vomiting within minutes of radiation exposure has a terrible prognosis and signifies a >8 Gy exposure. In a resource limited environment palliative care should be considered for patients with immediate vomiting after exposure.

Vomiting however is very non specific due to the many other external factors that can induce vomiting. Utilization of vomiting after radiation exposure should only be used as a guide rather than an absolute rule when treating patients with radiation injuries. Overall a combination of clinical presentation, onset of vomiting, and absolute lymphocyte count should will help give a complete picture of the patients prognosis.

Medical Management

Rule number 1 is always protect yourself and the staff. Generally speaking, most radiation exposures take several days to fully manifest and those who are actively dying from a radiation exposure when presenting to the ED have received a radiation dose that is not compatible with life. - PPI - Decontamination - Life saving interventions Symptomatic care - ATLS – ABCDEs - Anti emetics for vomiting and IV fluids - Treat radiation burns like thermal burns - Antibiotics for severe radiation injuries - Hematopoietic Simulating factors for if resources permit and the patient is stuck in the ED - Estimate radiation exposure for prognostication

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