Adapted from Donnelly et al, Acute Radiation Syndrome: Assessment and Management, Southern Medical Journal, 103:6, June 2010

Acute Radiation Syndrome (ARS)

Few clinicians will experience this first hand, therefore theoretical preparation is key to handling patients with radiation

exposure should a disaster arise. There are no pathognomonic signs or symptoms so it is difficult to diagnose without an

obvious history of exposure.

Pathophysiology More actively replicating cells are most sensitive to radiation.

Tissues affected most: gonads>bone marrow>GI>neuro>connective tissue>muscle>bone

3 classic ARS syndromes There is clinical overlap between the syndromes. Damage to increasingly radio-resistant cells is a marker of higher

absorbed dose and clinical severity.

Hematopoietic/Bone Marrow syndrome Occurs with exposure >200 rad

Lymphocytes depleted first, followed by granulocytes and platelets within days

Red cells less sensitive so rapid anemia is unusual (i.e. search for other causes e.g. bleeding)

Death occurs within weeks-months due to infection from impaired immunity or bleeding

Gastrointestinal syndrome Occurs with exposures between 600 – 1000 rad

Abrupt onset within hours of n°/v°, anorexia and crampy abdo pain

Vomiting suppressed >1000 rad

Diarrhea is an ominous sign

Death occurs from overwhelming sepsis, multi-organ failure, bleeding within weeks

Neurovascular syndrome At doses >1000 rad:“fatigue syndrome”: fever, headache, then altered reflexes, dizziness, confusion,

disorientation, ataxia, and loss of consciousness with increasing dose

At doses >3500 rad: damaged blood vessels →circulatory collapse, ↑ICP, cerebral vasculitis, meningitis

At doses >5000 rad: death within 48h before other syndromes can manifest

Phases All 3 syndromes have 4 phases:

Prodromal phase: n°/v°, fever, headache, parotitis, abdominal cramping, skin erythema, conjunctivitis, and

hypotension. Usually <48h duration. More rapid time to onset with higher dose.

Latent phase: hours to weeks of clinical improvement but stems cells are depleted.

Manifest phase: days to months of adverse health effects of each syndrome.

Recovery or death: recovery can take months to years. Patients exposed to very high dose die within days,

lower lethal doses cause death within weeks to months.

Farooq Khan MDCM PGY3 FRCP-EM

McGill University November 14

th 2011

Adapted from Donnelly et al, Acute Radiation Syndrome: Assessment and Management, Southern Medical Journal, 103:6, June 2010

Assessment Absolute lymphocyte count

Easy and quick, esp. In mass casualty

CBC q4h for first 8h, then q6h for next 40-48h

Initially low or progressively falling count is highly

suggestive of high dose radiation exposure (see

nomogram)

Time to vomiting

Caveats about time to vomiting

Non specific

Suppressed >1000 rad

50% sensitive at 200-300 rad

80-90% sensitive at 500-600 rad

Gold standard of dicentric chromosome assay is not offered at most sites and has long turnaround time (weeks)

Management

Prodromal phase Regardless of triage category:

History and physical examination

Removal of external contamination

Dose estimation

Symptomatic and supportive care (including

psychological support of the patient and family)

Replacement of fluids and electrolytes

Latent phase Estimate following factors that impact prognosis

Age and underlying health status

Magnitude of absorbed dose

Body volume irradiated

Illness severity

Concomitant infection, physical trauma, or

burn/dermal injury

Manifest phase Triage to minimal care, aggressive supportive care, or palliative care depending on prognosis

Transfer of individuals with hematopoietic syndrome to tertiary care centers specializing in the care of

pancytopenic patients (incl. ID and Heme for febrile neutropenia)

ANC<0.5×109 leads to higher infection rates

G-CSF (Neupogen) and GM-CSF can stimulating spared or resistant stem cells into repopulating bone marrow.

Stem cell transplants can also be done

Radiation emergency medicine consultation services provided by the Radiation Emergency Assistance Center/Training

Site (REAC/TS) with physicians and health physicists available 24/7 at 865-576-1005.

Figure 1 Andrews nomogram Curves 1 to 4 correspond roughly to the following whole-body doses: curve 1: 3.1 Gy (3,100 rad), curve 2: 4.4 Gy (4,400 rad), curve 3: 5.6 Gy (5,600 rad), and curve 4: 7.1 Gy (7,100 rad)