BACKGROUND Irradiation: definitions A high total level of exposure of the whole body can cause ARS. ARS appears further to whole-body irradiation at a high dose. It is clinically undetectable below 1 Gy. Its severity depends on the level of the dose received and its distribution in the body; some target systems of the organism are particularly radiosensitive, notably the hematopoietic system. The clinical development comprises four phases. The higher the dose received, the shorter and more intense each of the first three phases will be. The four phases 1. Prodromal phase or initial phase (initial syndrome): it lasts from a few hours to 48 hours at the most. 2. Latent period, clinically inapparent: its duration varies from 7 to 21 days; it is absent in cases of very high irradiation levels. 3. Critical phase or manifest phase: phase during which the clinical consequences of the tissular damage manifest themselves. 4. Recovery phase: at sub-lethal doses, recovery can take several months. Clinical signs The symptomology of radiation sickness is not specific and can be similar to a case of trauma or poisoning. ARS reflects the damage to various tissues: bone marrow, digestive system, respiratory system and the central nervous system. The higher the dose received and the larger the area of the body concerned, the earlier the clinical signs will appear. Five broad groups of victims are described below, in decreasing order of severity. Victims in groups I and II have a poor prognosis as there is no effective treatment at present. CLINICAL SIGNS BY GROUP OF VICTIMS Groupe I • State of shock • Cardiovascular collapse • Loss of consciousness Doses >25 Gy Groupe II • Painful oedema of the parotid glands • Neurological signs (disorientation, convulsions, mental clouding) • Neurovegetative and vasomotor signs (hyperthermia, vigilance disorders, tachycardia and cardiac rhythm disorders) • Asthenia, anorexia Doses >12 Gy Groupe III • Nausea, vomiting, diarrhoea • Headaches, pains in the parotid glands, dry mouth, drowsiness • Variable hyperthermia • Asthenia, anorexia Doses of between 2 and 12 Gy Groupe IV • Nausea, vomiting, drowsiness, headaches, dry mouth • Asthenia (difficult to objectivise) • Anorexia Doses of between 1 and 2 Gy Groupe V • The absence of early clinical signs does not exclude the possibility of irradiation at less than 1 Gy. • Hospitalisation is not indispensable, but a biological assessment must be proposed in order to confirm whether or not irradiation has occurred. SEE SHEET 12 Doses <1 Gy Acute radiation syndrome (ARS) 08 SHEET 11 MEDICAL RESPONSE IN NUCLEAR OR RADIOLOGICAL EMERGENCY 41
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