Pediatric emergency medicine trisk 495

FIGURE 90.11 The effect of distance on radiation exposure from a point source of radiation.

Recognition
Radiation exposures can be recognized by understanding three questions: (i) Who
is likely to be affected by a radiation exposure or accident? (ii) What are the
likely sources of radiation? and (iii) What are the likely injuries? The people most
likely to be involved in a radiation exposure event are individuals whose work
involves radiation. Other individuals who may be exposed to radiation include
members of the general public who inadvertently come into contact with a
radiation hazard, for example, the population surrounding a nuclear powerplant,
those who are intentionally poisoned, and patients who have undergone medical
procedures (e.g., fluoroscopy or radiation therapy). To cause a significant
radiation injury, an intense radiation source is needed. The four major types of
possible intense radiation sources are listed in Table 90.12 . Because of their
various physical properties, different sources are likely to cause different types of
radiation injuries.
Radiation induces injury either through exposure or contamination. Because
patients exposed to radiation do not have radioactive elements on or in them, they
do not emit radiation and can be treated without any additional precautions on the
part of healthcare workers. Two types of injury from radiation exposure are


possible—whole body and local injury. A high dose of penetrating radiation over
a short period of time to a large portion of the body (i.e., whole-body radiation)
causes the acute radiation syndrome. Large doses of radiation over a short period
of time to a small portion of the body cause a local radiation injury. Analogous
medical situations would be whole-body radiation as conditioning for bone
marrow transplantation and localized radiation therapy for breast cancer. The
signs and symptoms of the acute radiation syndrome ( Table 90.13 ) begin to
appear after whole-body radiation doses of approximately 1 Gy. Organs with
rapidly dividing cells such as bone marrow and GI tract lining are the most

susceptible to radiation damage. The amount of damage that occurs is dependent
both on the dose and on the dose rate, for example, a dose of 1 Gy/min would
probably cause symptoms but 1 Gy at a dose rate of 10 mGy/day for 100 days
would likely be asymptomatic. Acute doses of about 4 Gy may be lethal in
approximately 50% of people if they do not receive medical treatment. With
maximum medical treatment, the dose of radiation that will kill 50% of people
may be as low as 6 Gy.


TABLE 90.12
INTENSE RADIATION SOURCES
Type of source

Examples

Likely injuries

Sealed

Industrial radiography

Contamination unlikely

Brachytherapy

Local radiation injury with
small source

Some radiation therapy
machines

Industrial sterilizers

Whole-body exposure with
large source

Unsealed

Medical radionuclides (e.g., External and internal
131 I, 32 P)
contamination likely
Accidental release by a
reactor
Radium dial painters

Radiation devices

Cyclotron
Linear accelerator

Uncontrolled
fission

Fluoroscopy unit
Nuclear reactor
Uranium enrichment

Local radiation injury likely

Large whole-body doses
likely

On- and off-site
contamination possible
for nuclear reactors

Weapons production
The acute radiation syndrome consists of three distinct phases ( Table 90.14 ):
prodromal, latent, and manifest illness. The prodromal phase begins minutes to
hours after the radiation exposure, lasts for 2 to 3 days, and common symptoms
are nausea, vomiting, diarrhea, fatigue, and/or headache. The prodromal phase is
followed by the latent phase, in which the patient is relatively asymptomatic and
generally lasts days or weeks after the exposure. The manifest illness phase poses
the greatest risk for infection and bleeding due to bone marrow suppression and
GI epithelial damage. As the radiation dose increases, the duration of the
prodromal phase increases and the length of the latent phase decreases.


TABLE 90.13
DOSE–EFFECT RELATIONSHIP AFTER ACUTE WHOLE-BODY
RADIATION EXPOSURE
Whole-body
absorbed dose
(Gy)

Comments

0.1

Asymptomatic (minimal detectable dose using
cytogenetics)
Asymptomatic (minor depression of white blood cell and

platelets)
Nausea and vomiting in approximately 15% of patients
within 2 days of exposure

0.5
1
2
4

6

Nausea and vomiting in most patients
Nausea, vomiting, and diarrhea within 48 hrs; severe
hematologic depression; 50% mortality without medical
treatment
100% mortality within 30 days without medical treatment;
50% mortality with medical treatment

7

Gastrointestinal syndrome; survival unlikely; death in 2–3
wks

50

Cardiovascular/Neurovascular syndrome; death in 24–72
hrs

With doses of 2 to 4 Gy, the primary effect of whole-body radiation is to
depress the bone marrow. Although the absolute lymphocyte count ( Fig. 90.12 )

decreases rapidly within the first 24 hours, there is no need for specific medical
treatment. The patient will be at greatest risk 3 to 4 weeks after the radiation
exposure when the total white blood cell, neutrophil, and platelet counts reach a
nadir ( Fig. 90.13 ). At this time, the patient is vulnerable to death from infection
and bleeding. If the patient can be supported during this period of vulnerability
and if the bone marrow is not irreversibly damaged, a recovery phase ensues.
The gastrointestinal syndrome occurs from absorbed doses of more than
approximately 7 Gy. During the prodromal phase there is prompt onset of severe
nausea, vomiting, and diarrhea. There is a latent period of approximately 1 week
and then recurrence of GI symptoms, sepsis, electrolyte imbalance, and likely