From the Guidelines
The pathophysiology of acute radiation syndrome (ARS) involves damage to the hematopoietic, gastrointestinal, and cerebrovascular systems, leading to a range of clinical syndromes that can be divided into four phases: prodromal, latent, manifest illness, and recovery or death 1.
Clinical Syndromes
- Hematopoietic Syndrome: characterized by damage to bone marrow stem and progenitor cells, resulting in pancytopenia, infection, bleeding, and poor wound healing 1.
- Gastrointestinal Syndrome: marked by vomiting, severe diarrhea, high fever, and malabsorption, leading to malnutrition, dehydration, and electrolyte derangements 1.
- Cerebrovascular Syndrome: characterized by disorientation, confusion, prostration, and seizures, with a rapid decline in condition, often resulting in death within 2 days 1.
Treatment
Treatment of ARS involves supportive care, including fluid replacement, electrolyte management, infection control, and wound care 1. In severe cases, bone marrow transplantation may be necessary to restore hematopoietic function 1.
Radiation Exposure
The severity of ARS depends on the dose and dose rate of radiation exposure, with higher doses resulting in more severe symptoms and a poorer prognosis 1. The time course of clinical manifestations can vary depending on the dose and dose rate, with symptoms appearing within hours to weeks after exposure 1.
From the Research
Pathophysiology of Acute Radiation Syndrome (ARS)
- The acute radiation syndrome (ARS) occurs after whole-body or significant partial-body irradiation, typically at a dose of >1 Gy, and can involve the hematopoietic, cutaneous, gastrointestinal, and neurovascular organ systems either individually or in combination 2.
- There is a correlation between the severity of clinical signs and symptoms of ARS and radiation dose, with higher doses leading to more severe symptoms 2.
- Radiation-induced multi-organ failure (MOF) describes the progressive dysfunction of two or more organ systems over time, and radiation combined injury (RCI) is defined as radiation injury combined with blunt or penetrating trauma, burns, blast, or infection 2.
Phases of ARS
- The phases of ARS include:
- Prodromal: 0-2 days from exposure
- Latent: 2-20 days
- Manifest illness: 21-60 days from exposure 2
- The natural history of ARS presents a 60-d time segment of multi-organ sequelae that is concomitant with the latent period or time to onset of the evolving multi-organ injury of the delayed effects of acute radiation exposure 3.
Treatment of ARS
- Treatment of ARS includes:
- Granulocyte-colony stimulating factor (G-CSF) at a dose of 5 μg/kg body weight per day subcutaneously for neutropenia 2
- Antibiotics, antiviral, and antifungal agents for prevention or treatment of infections 2
- Stable iodine in the form of nonradioactive potassium iodide (KI) to saturate iodine binding sites within the thyroid and inhibit incorporation of radioiodines into the gland, if taken within the first hours of contamination 2
- Hematopoietic stem cell (HSC) transplantation if severe aplasia persists under cytokines for more than 14 days 2
- Countermeasures of potential benefit include cytokines and for a subgroup of hematopoietic syndrome (HS) patients, hematopoietic stem cell transplantation 4.
- Management of non-HS subsyndromes is supported by a narrative review of the literature and recommendations of infectious disease societies 4.
Clinical Management of ARS
- Clinical management of ARS requires a multidisciplinary approach, with consideration of radiation-induced multi-organ dysfunction syndrome (RI-MODS) and failure (RI-MOF) 5.
- Patients with severe ARS due to whole-body exposure require management at institutions where multidisciplinary, resource-intensive therapy can be provided 5.
- The European triage system (METREPOL) can be used to evaluate the severity of radiation injury and score groups of patients for general and specific management of the syndrome 2.