The logistics surrounding medical countermeasures - who receives them, which ones, when, and where - are important factors that impact how clinicians and public health officials plan for and deliver care in a radiation emergency. How individuals are assessed for radiation exposure and how they are triaged to receive medical countermeasures are processes especially relevant for providing efficient and effective emergency care.
This section outlines the basic assessment steps used to identify internal contamination, and the benchmarks used to guide the determination of need for medical countermeasures, including discussion of considerations for scenarios involving limited resources.
Before discussing the steps involved in the evaluation of a patient with internal contamination, we should pause to note that whenever possible, clinicians should work with radiation health professionals to perform the evaluation steps and for guidance on the interpretation of test results. Radiation health professionals have expertise on matters of radiation detection, quantification, and health effects that will greatly enhance the clinical evaluation and treatment of patients with radiological exposures.
As individuals present for medical care, they will likely be processed through an established triage system. During a radiation emergency, additional assessments are added to triage algorithms to inform clinical decisions and to plan care for the immediate and delayed needs of patients with radiation injuries.
As part of the emergency response operation, many individuals will present to staging areas, like community reception centers, which are set up to handle large numbers of individuals presenting for radiation screening and decontamination. Other individuals may present to medical facilities separate from this staging process, and would require radiation screening and decontamination at the facility. Further still, patients in critical status may not have had time prior to or during transport for full radiation screening, and may need decontamination once they are stabilized.
Because there is the chance that patients may present with minimal information and some amount of external contamination still present, clinicians and staff may be worried about their own safety when providing care. It is therefore important to know that real world experience suggests there is minimal risk to healthcare providers and staff when appropriate protective equipment is worn and protective actions taken. Based on this, it is equally important to note that regardless of a patient’s contamination status, emergency medical stabilization and resuscitation should come first and should NOT be delayed to perform decontamination. Life-saving interventions should always be performed without delay.
To determine whether a patient would benefit from treatment with a medical countermeasure a thorough evaluation must first take place. Elements of this evaluation include:
1. A focused radiation exposure history including assessment for adverse health effects
2. A radiation survey with detection equipment
3. Laboratory testing
A focused radiation exposure history can provide a crude estimate of the dose of radiation a patient may have received and prioritizes exposure information related to patient location, time, and duration. Important questions to ask include where exactly the patient was located during an incident, and for how long the patient remained in the area. Location provides information both about proximity to the radioactive source and also information about potential shielding from external sources of radiation. Questions regarding the presence and timing of symptoms, particularly vomiting, diarrhea, and elevated core body temperature, can be critical for making preliminary estimates of radiation dose and planning potential care needs. Information regarding the type of radioactive material involved in the incident will likely need to be collected from other sources as it becomes available.
A radiation survey is completed as soon as possible to provide additional details on the presence and amount of radiological contamination. Radiation surveys can take many different forms and use a wide variety of detection equipment ranging from handheld detectors to portal monitors; pre-existing emergency plans and radiation health professionals will determine the appropriate type of survey to perform in a given situation. External contamination found on or near the nose or mouth raises the possibility of internal contamination via inhalation or ingestion, as does contamination found over a wound. Internal contamination may also be suggested when a survey finds a radiation hotspot over a part of the body that persists despite repeated attempts to decontaminate.
Laboratory testing can help determine the presence, type, and quantity of internal contamination and also help quantify the radiation dose absorbed by the body. Tests that help to diagnose internal contamination include measuring radioactivity in different types of samples that could include nasal swabs, urine, or stool. Other tests using specialized radiation detection equipment, like whole body counting, can directly measure the amount of radioactivity in a person’s body. Tests that can help quantify the radiation dose absorbed by the body include serial lymphocyte counts and specialized chromosomal analysis called cytogenetic biodosimetry. Clinicians should understand that there is limited capacity to perform specialized laboratory radiation testing and receiving results of specialized tests will take time. However, basic radiation survey equipment in the hands of a qualified radiation professional can provide a great deal of information about the nature of an exposure and be used to initially direct medical care while awaiting results of specialized tests.
Taken together, the patient exposure history, radiation survey, and laboratory testing are used to diagnose the presence, type, and amount of internal contamination or significant radiation exposure. Clinicians, with the help of radiation health professionals, will compare this data to existing benchmarks to understand the radiation dose and determine whether treatment with medical countermeasures is warranted.
One prominent benchmark used to determine when treatment with medical countermeasures can be beneficial for patient who is internally contaminated with a specific radionuclide is the Clinical Decision Guide (or CDG). Clinical Decision Guides will be explained in more detail later on in this module.
Once the patient has been assessed and the results compared to appropriate benchmarks, a clinical decision can be made regarding patient triage level and the allocation of medical countermeasures. Normally, the presence of internal contamination by a radionuclide that has an available countermeasure would be a strong indicator for treatment. However, when shortages in medical countermeasures occur, as can be expected in large-scale incidents, public health and clinical guidance may moderate when and to whom countermeasures are given.
The triage of patients who may need medical countermeasures will be specific to the emergency at hand and the amount of available supplies, but in general terms, public health officials may use prodromal symptoms, laboratory results, and injury status as parameters to manage and direct those resources.
Severe prodromal symptoms – including diarrhea, nausea and vomiting within minutes of exposure, and central nervous system manifestations like loss of consciousness, coma, fever, and shock – suggest a rapid, terminal prognosis, and therefore may be used allocate medications to those with better chances of survival.
Lymphocyte counts are very sensitive to radiation exposure and therefore can serve a similar role in identifying the dose of radiation received by individuals. If a rapid rate of decline is observed – for example, if over two days there is a 50% decrease in absolute lymphocyte count to less than 1000 cells per microliter – a clinician can assume at least a moderate radiation dose and provide treatment accordingly.
And similar to non-radiation triage, the severity of injury also plays a role in determining the likelihood of survival. Individuals with severe combined injury - extensive traumatic injuries or burns plus a high dose of radiation – may be triaged to an expectant level compared to those without combined injury when resources are limited.
Following triage protocols adapted for a radiation emergency is a critical planning step for the responsible provision of medical countermeasures, and with practice can be successfully integrated into the system of care.
The four different medical countermeasures that could be used during a radiation emergency are:
1. Potassium Iodide (KI)
2. Diethylene triamine pentaacetic acid (DTPA)
3. Prussian blue insoluble
4. Colony Stimulating Factors
The first three countermeasures are only relevant after internal contamination with a few specific radionuclides. KI is indicated for radioactive iodine exposure and prevents its incorporation in the thyroid. Prussian blue and DTPA are indicated for a number of other radionuclides, and promote the excretion of those radionuclides from the body.
Colony stimulating factors are not radionuclide specific, but can aid in the regeneration of the hematopoietic system after radiation-induced bone marrow injury. At the present time colony-stimulating factors are not FDA-approved for radiation-induced bone marrow suppression. However, plans exists which could result in their availability and use under an FDA-approved emergency use authorization.
In addition to these four countermeasures, there are other supportive medications that will likely be needed. Patients with radiation injuries may have nausea, vomiting, fever, diarrhea, dehydration, bleeding, infection, and pain. Additional useful medications include antiemetics, antidiarrheals, antibiotics, analgesics, intravenous fluids, blood products, and nutritional supplements. Careful planning for additional supplies in these categories may be needed in mass-casualty incidents.