30. Acute Radiation Syndrome - Definition, Stages, Clinical Features

Acute Radiation syndrome- Definition. Stages. Clinical features

Written by Anam Hussain

Definition:

Acute radiation syndrome is defined as a combination of clinical syndromes occurring in stages during a period of hours to weeks, after exposure. Injury to various tissues and organs is expressed.

Acute Radiation syndrome is subdivided into 3 main syndromes

• Hematopoietic syndrome
• Gastrointestinal syndrome
• Cerebrovascular syndrome

Each of these sub-syndromes are divided into 4 main stages:

• Initial/prodromal stage
• Latent phase (becomes shorter with increasing dose)
• Manifest phase (when clinical symptoms are expressed, depends on dose and type of radiation)
• Recovery (or death) phase

1. Haemopoietic syndrome

• Platelet count drops after exposure to IR
• Red blood cells usually show no depression or very mild depression in count after exposure to IR, unless there is concomitant haemorrhage
• Granulocyte count shows initial paradoxical rise after exposure to dose greater than 2 Gy
• First blood line affected: white blood cells
• First peripheral change in blood count: lymphopenia
• Damages in bone marrow lead to haemopoietic syndrome. These damages cause pancytopenia
• Prodromal symptoms: nausea, vomiting but are mild compared to other syndromes. Lack of CNS syndrome signs, change in BP, mild/water diarrhoea
• Latent phase: lasts up to a month. Relatively asymptomatic except for some tiredness and fatigue
• Manifest illness phase: neutropenic fevers, sepsis, haemorrhages, systemic and localised infections.

2. Gastrointestinal Syndrome

• Occurs at doses >10 Gy of gamma rays or equivalent
• Causes reproductive death of mucosal crypt stem cells
• Depletion of epithelial cells lining the lumen of GI tract results in:
• Intestinal bacteria gaining free access to body, haemorrhage through duodenal areas, loss of absorptive capacity
• Prodromal stage: occurs within 30min-2hrs of exposure. Symptoms of vomiting, nausea and occasional diarrhoea with abdominal cramps. Symptoms are accompanied with drowsiness and fatigue. Symptoms continue but diminish 48 hours after exposure
• Latent stage: patient is asymptomatic for hours to days but is markedly weak and tired
• Manifest clinical illness phase: return of severe diarrhoea, vomiting and diarrhoea with fever, bloody diarrhoea, shock and death. Complications with this phase include: simultaneous invasion of endogenous/pathogenic bacteria into blood stream, malabsorption, parlaytic ileus, GI bleeding

3. Neurovascular syndrome

• Identified at doses above 30 Gy
• Prodromal stage: begins in less than an hour within minutes of exposure. Symptoms include: burning sensation, severe nausea, projectile vomiting, bloody diarrhoea, hyperpyrexia, disorientation, cutaneous edema and erythema, lack of coordination and possibly seizures. Severe symptoms may last more than 24hrs
• Latent stage: is brief with apparent clinical improvement. Lasts only hours to days