Pediatric emergency medicine trisk 496

death. The patient is susceptible to infection due to lack of granulocytes and
because pathogens can readily enter the body across the damaged GI tract lining.
At dose levels of more than 50 Gy, the cardiovascular/neurovascular syndrome
predominates. There is almost immediate nausea, vomiting, prostration,
hypotension, ataxia, and convulsions. The permeability of blood vessels increases
and there is brain edema and hypotension caused by the difficulty of maintaining
a normal intravascular space. Death usually occurs within 1 to 4 days.
TABLE 90.14
ACUTE RADIATION SYNDROME—SYMPTOMS
Prodromal (0–2 a )

Latent (2–20 a )

Fatigue
Nausea and vomiting

Generally asymptomatic Sepsis
Bleeding
Diarrhea

Diarrhea
Headache
Dizziness
a Days

after exposure.

Manifest illness (21–60
a)

FIGURE 90.12 Effect of whole-body radiation on lymphocytes in the first 2 days after
exposure.

Estimating the whole-body radiation dose may be difficult, especially when
complicated by injuries that are not due to radiation. The signs and symptoms
during the prodromal period are quite nonspecific except for a rapidly decreasing
lymphocyte count. Nausea and vomiting are sensitive but nonspecific symptoms.
Patients who do not have nausea and vomiting are unlikely to have been exposed
to a radiation dose that is large enough to cause acute radiation syndrome.
However, individuals may have nausea and vomiting for reasons other than
exposure to radiation. The whole-body radiation dose from radiation accidents is
rarely uniform. The nonuniform nature of the radiation dose makes it more
difficult to predict the biologic effects from the exposure. Chromosome analysis
(cytogenetic dosimetry) may be helpful in estimating the radiation dose, but the
results may not be available for about 1 week.
The second type of radiation exposure that can occur is local exposure, which
involves a radiation dose to a small part of the body. Large doses can be tolerated
if only a small part of the body is exposed. Local radiation injuries may cause
bone marrow depression if accompanied by a significant whole-body radiation


dose. Local injuries are rarely life threatening, but they are difficult to manage
because they often cause a slowly progressive injury that takes months and
sometimes years to fully evolve. The injury develops slowly because the radiation
causes progressive fibrosis of the blood vessels, which, in turn, causes tissue
necrosis. The ultimate extent of the injury may not be appreciated initially.
Healing following amputation or reconstructive surgery is poor because of
deficient blood supply.
TABLE 90.15
APPROXIMATE ABSORBED DOSE TO PRODUCE SKIN CHANGES

FROM LOCAL RADIATION INJURY
Absorbed dose
(Gy)

Findings

3-6

Threshold for erythema

15
20

Moist desquamation
Skin ulceration with slow healing

>30

Gangrenous changes

The hand is the most common site for localized radiation injuries. The next
most common sites are the thighs and buttocks because individuals are likely to
put things that they find into their pockets. A patient who has undergone a
fluoroscopic procedure could have local radiation injury to the skin overlying the
region imaged. For example, the radiation source is typically positioned posterior
to a patient undergoing a cardiac catheterization and therefore a radiation burn
would be on the back. Most industrial radiography sources deliver an extremely
high radiation dose. In contrast, analytical x-ray crystallography machines, which
emit x-rays of much lower energy than the photons of 192Iridium, are not likely
to cause deep blood vessel injury.

Local radiation injuries can typically be differentiated from thermal burns. The
effects of a thermal burn appear immediately. If a patient presenting with a burnlike injury does not know the cause or time of the injury, a local radiation injury
should be suspected. Table 90.15 lists the dose-related findings expected after an
acute local radiation exposure.
If erythema is seen within the first 48 hours, ulceration may occur later. The
erythema may come in waves that appear, disappear, and then reappear. With
transepidermal injury, blister formation may occur at 1 to 2 weeks with doses in


the range of 100 Gy and at 3 weeks after dose levels of 30 to 50 Gy. Treatment is
required to prevent infection and to relieve pain. Skin grafting, especially
musculocutaneous flaps, may be appropriate if the radiation exposure was
localized and superficial. Progressive gangrene, due to the obliterative changes in
the small vessels, will occur if the radiation exposure is large and involves deep
structures. Under these circumstances, amputation may be necessary.

FIGURE 90.13 Effect of whole-body radiation on blood cell counts in the days after exposure.

Contamination
Contamination represents the other major type of radiation injury. Contamination
occurs when radioactive dirt or liquid remains on the patient (external
contamination) or, when inhaled or ingested, inside the patient (internal
contamination). Contamination is the only type of radiation injury that requires
the medical staff to take radiation-related precautions. Although there is usually
little danger to the medical staff when caring for a contaminated person once they
are in the hospital, medical personnel who respond to the accident site may be
exposed to large, potentially life-threatening doses of radiation. For these rescue
workers, 0.5 Gy is the voluntary limit suggested by the National Council on
Radiation Protection and Measurements (NCRP) for lifesaving activities.
External contamination. External contamination rarely is a significant

medical problem. To prevent additional radiation exposure to the patient, medical
staff, and the public, external contamination should be removed, and dispersal of
radioactive materials should be prevented. The goal of treatment of any
contaminated patient is to keep radiation exposures “as low as reasonably
achievable.” This is called the ALARA principle and requires advance planning,
specific supplies, and appropriate protective clothing. Preventing the dispersal of