ACUTE RADIATION SYNDROME

Acute Radiation Syndrome is a combination of clinical signs and symptoms occurring in stages over a period of hours to weeks due to a significant partial-body (70%) or whole-body exposure of > 1 Gy (100cGy of ionizing radiation), as injury to various tissues and organs is expressed. ARS is caused by >1 Gy / 100 rad whole-body doses of ionizing radiation. ARS follows a predictable clinical course through four phases: 1) prodromal, 2) latent, 3) manifest illness, 4) recovery or death. The transition time between phases depends on the dose of radiation absorbed. The higher the whole-body dose, the shorter each of the phases. Table 8 below depicts time to onset of prodromal symptoms based on dose.16

Figure 2. Time to Emesis

Nausea, vomiting, diarrhea, fever, and transient skin erythema characterize the prodromal phase, which may last minutes to days. The patient may then appear well for a few hours, or even a few weeks during the latent phase, which is characterized by silent cell and tissue destruction. This destruction is later manifested clinically as one or more of three syndromes: 1) hematopoietic (H-ARS), 2) gastrointestinal (GI-ARS), 3) neurologic (N-ARS). Death can occur within days for gastrointestinal and neurologic but may not occur for weeks for hematopoietic.14,17-18

Without treatment, the LD50/60 for ionizing radiation is about 4 Gy. With appropriate intervention and treatment, the dose goes up to about 6 Gy. Experience from those who receive even higher doses suggest that with aggressive resuscitation and critical care, survival can be extended by months. This factor can lead to the eventual need to evacuate these casualties.14

Table 8. Acute Radiation Syndromes

Sequelae in doses less than 1 to 2 Gy can take more than two weeks to manifest. In a mass casualty producing event, those with mild doses of 1-2Gy without trauma, could be observed as outpatients and evacuated using non-medical platforms. These casualties should be continually observed and regularly re-evaluated for deteriorating health status. Casualties exposed to moderate to severe doses (>2Gy) should be hospitalized and prioritized for evacuation to reach specialty care prior to onset of manifest illness. Supportive care is the mainstay of treatment for patients in the prodromal phase of ARS and can be managed at Roles 1-3, or in a prolonged field care setting, while pending evacuation.

Therapy which may be necessary pending movement to definitive care is outlined In Table 9. Consider early consultation with hematology/oncology and/or the advisor line for symptom management/treatment of acute radiation syndrome.

Figure 3. Radiation effect on complete blood
Figure 4. Dose estimates using blood lymphocyte kinetics
Figure 5. Nuclear detonation in a deployed setting
Table 9. Acute radiation syndrome therapy