RC-7a The Medical Diagnosis and Treatment of Radiation Overexposed People

Although rare, accidental irradiation overexposures remain difficult to treat, mainly because of a complex physiopathology, known as the acute radiation syndrome (ARS). As a consequence, the issue remains fatal for most of high dose radiation accident victims. This is due in part through the lack of biological indicators able to give information about the extent of radiation-induced damage. Such bio-indicators may help to define a therapeutic strategy adapted to each specific accidental overexposure situation. Recent radiation accidents such as the Tokai Mura accident clearly showed that the therapeutic strategy must be based on the estimate of radiation-induced damage to life threatening physiological systems rather than the dose received by the victim. In fact, these accidents highlighted the heterogeneity of accidental irradiation, even in the most severe cases. Thus, important conceptual changes appeared recently for the treatment of radiation accident victims, such as the questionable role of haematopoietic stem cell transplantation after heterogeneous irradiation. Moreover, growing evidence indicates that ARS should be considered as an interplay of multiple pathologies originating not only from the haematopoietic system, the gastro-intestinal tract and the skin, but also from the neuro-vascular system and the inflammatory reaction rather than the addition of individual syndromes appearing in an ordered fashion according to the radiation dose and the time post-irradiation. Thus, it is important to take into account these new concepts in the medical management of accidentally overexposed victims. 2 1The acute radiation syndrome: historical concepts Classically, the acute radiation syndrome, which is defined as the pathologies developing after an uncontrolled radiation overexposure, is described as appearing in three phases (Figure 1). The first one, the initial syndrome, appears in the first few hours after irradiation. Manifestations are nausea, retching and vomiting, reflex diarrhoea, headache, hypotension, and in the most severe cases, a transient incapacitory syndrome. Additionally, erythema and oedema may transiently appear when local high dose irradiation was received. Importantly, the time of onset, intensity and duration of these symptoms are directly proportional to the global radiation dose received by the victim. Thus, the initial syndrome must be accurately observed, since it constitutes the very first indicator of the severity of radiation-induced damage to the victim (Young, 1987).