Total body irradiation Flashcards
An employee working in a nuclear power plant is accidentally exposed to a total body y-ray dose of 2 Gy. Ten days after the accident, you draw blood and submit it for hematologic analysis. Which of the following would you expect to see?
A. A decrease in hemoglobin concentration and platelet counts
B. A decrease in platelet count and an increase in lymphocyte count
C. A decrease in lymphocyte count, but no effect on hemoglobin concentration
D. An increase in neutrophil count, but no effect on hemoglobin concentration
E. No effect on lymphocytes, hemoglobin, neutrophils or platelets
C
Ten days after a total body dose of 2 Gy, one would expect lymphocyte and neutrophil counts to decrease, but hemoglobin concentration and platelet counts to remain normal. Platelets will not decrease until ~20 days after a 2 Gy exposure. Hemoglobin will not decrease unless much higher doses are received and a longer time period has elapsed.
A terrorist preparing a “dirty bomb” containing 210-Po received a total body dose equivalent of approximately 8 Sv resulting from an accidental ingestion of this radioisotope. He did not seek medical attention and died 7 days later from acute radiation toxicity. Which of the following would you expect to see at autopsy?
A. Complete bone marrow aplasia
B. Mitotic arrest of intestinal crypt cells
C. Cerebral edema
D. Microvasculitis
E. Brain necrosis
B
This individual will experience the GI syndrome and die before his bone marrow would become completely aplastic, although there probably would be some hypoplasia in the marrow, spleen, and lymph nodes. A characteristic feature observed in people who die from the GI syndrome is mitotic arrest in the intestinal crypt cells. The other listed changes (cerebral edema, microvasculitis, brain necrosis) would be expected with the cerebrovascular syndrome, which would not occur unless the total dose received was at least 3-4 fold higher than 8 Sv.
Which of the following pairs of total body radiation effects and approximate threshold dose is CORRECT?
A. Gastrointestinal syndrome – 2 Gy
B. LD50 (no medical intervention) – 3.5 Gy
C. LD50 (best current medical treatment) – 15 Gy
D. Cerebrovascular syndrome – 5 Gy
E. Hematopoietic syndrome – 0.2 Gy
B
Estimated human LD50 (dose to result in lethality in 50% of an irradiated population) is 7 Gy with the best medical intervention and 3.5 Gy without any medical intervention. The dose thresholds for the hematopoietic, gastrointestinal, and cerebrovascular syndromes are roughly 2 Gy, 8 Gy and 20 Gy, respectively. Death at 30-60 day, 5-16 days, hours-2 days respectively.
The death of a person 30-60 days following a total body radiation dose close to the LD50 (no medical intervention) would likely be due to damage to the:
A. Heart
B. Bone marrow
C. Central nervous system
D. Brain
E. Gastrointestinal system
B
The death of a person 30-60 days following a total body radiation dose close to the LD50 would be due to damage to the bone marrow, resulting in the gradual reduction in the level of peripheral blood elements. Infection due to loss of white blood cells and/or hemorrhage due to the loss of platelets are typically the cause(s) of death. Usually, death from ablation of the bone marrow would not be manifest until about a month or two after irradiation; this is a reflection of the normal turnover rates of the mature blood components, which would not be replaced in the absence of functioning bone marrow stem cells. Death from radiation damage to the heart, liver, or kidney would not occur within two months following irradiation. Death due to damage to the gastrointestinal system usually takes place within 5-16 days following irradiation and would not be likely with a dose near the LD50 since it requires higher doses to manifest.
Which of the following statements is correct? After total body irradiation, the prodrome of the radiation syndrome:
A. Is not seen unless doses exceed 10 Gy
B. Occurs after the exposed person has recovered from the GI syndrome
C. Can be ameliorated through treatment with amifostine approximately 3-5 hours after the exposure
D. Includes GI symptoms such as anorexia, nausea, and vomiting that occur within minutes to hours following exposure and lasting hours to days, depending on the radiation dose
E. Is characterized by hematopoietic system damage, but no effects related to the gastrointestinal system
D
The prodrome of the radiation syndrome is a spectrum of early symptoms that occur shortly after whole body irradiation, lasts for a limited amount of time, and varies in time of appearance, duration, and severity depending on the dose. GI symptoms such as anorexia, nausea, and vomiting occur when an individual is exposed to doses near the LD50; at higher doses, symptoms such as fever and hypotension are also seen. The radioprotector amifostine would not be expected to ameliorate these symptoms if given after irradiation.
Following a total body dose of 12 Gy in one fraction, an exposed individual will not show the bone marrow syndrome because:
A. Higher doses than 12 Gy are needed to cause the bone marrow syndrome
B. The individual will likely die within 5-16 days from the GI syndrome, before overt symptoms of the bone marrow syndrome occur
C. This dose is not sufficiently high to cause any radiation syndrome
D. A bone marrow transplant will likely have been given and would mask the symptoms of the bone marrow syndrome
E. At this dose the radiation syndrome prodrome will be so severe it will overshadow the bone marrow syndrome
B
Following a total body dose of 12 Gy, an irradiated individual will likely die within 5-16 days from the GI syndrome. Thus, death will occur before the symptoms of the bone marrow syndrome are manifest, usually starting at about 20 days and resulting in death at 30-60 days. The bone marrow syndrome, resulting from damage to bone marrow stem cells, occurs after doses in the 2-8 Gy region.
For individuals accidentally exposed to radiation, a bone marrow transplant is potentially useful when the radiation dose is within a narrow range. That dose window is approximately:
A. 1-2 Gy
B. 3-4 Gy
C. 8-10 Gy
D. 15-20 Gy
E. Bone marrow transplants have no potential usefulness at any dose
C
Bone marrow transplants are only useful when the radiation dose to the exposed person is within about 8-10 Gy. At lower doses, an exposed person will likely survive with appropriate medical care. For doses above 10 Gy death from effects on the GI tract will occur even despite use of all effective currently available treatments.
Which of the following statements is FALSE regarding the symptoms that make up the prodrome after total body irradiation:
A. After receiving 2 Gy, the majority of those affected experience nausea and vomiting within 30 minutes
B. Serotonin-receptor antagonists are recommended in the management of nausea and vomiting after total body irradiation
C. Time to onset of prodromal symptoms is inversely related to radiation dose
D. Diarrhea is a prodromal symptom
E. The severity of prodromal symptoms is directly related to radiation dose
A
After exposure to 2 Gy, 50% or less will experience nausea and vomiting. Typically, this occurs within 2-6 hours of exposure. The majority of those who receive greater than 10 Gy would be expected to show prodromal symptoms by about 30 minutes after exposure. Symptoms of the prodromal syndrome after a sublethal exposure to total body irradiation include fatigue, anorexia, nausea and vomiting. The onset of these symptoms are inversely proportional to the dose of the exposure. In individuals who receive a supralethal dose of total body irradiation, additional prodromal symptoms include fever, immediate diarrhea, apathy, headache and hypotension.
Which of the following is NOT recommended as part of routine management of the gastrointestinal radiation syndrome after accidental total body irradiation:
A. Antiemetics
B. Antibiotics
C. Antidiarrheals
D. Corticosteroids
E. Oral nutritional support
D
Systemic corticosteroids are not recommended in management of patients with gastroinstestinal syndrome from total body irradiation. Supportive care (including psychological support), symptomatic treatment (50HT3 antagonist antiemetics, etc.), and fluid/electrolyte replacement (PO and/or IV) should be the earliest goals of medical management.
With recent advances in supportive measures to manage acute radiation exposure, what syndrome has been seen following exposure to 8-10 Gy in modern nuclear reactor accidents?
A. Pulmonary
B. Renal
C. Endocrine
D. Musculoskeletal
E. Hepatic
A
Pulmonary syndrome has been found to occur in nuclear reactor workers who were exposed to 8-10 Gy and survived hematopoetic syndrome due to modern supportive care with isolation, IV hydration, transfusions, antibiotics and hematopoetic colony stimulating factors. These patients died at approximately 130 days after exposure due to pneumonitis
