Biomedical Engineering Reference
In-Depth Information
been used to treat plutonium and americium toxi-
city. Given intravenously or intramuscularly, it has
significant side effects, including gastrointestinal
upset, pain at the injection site, bone marrow
depression, and nephrotoxicity.
The chelator DTPA (diethylenetriaminepen-
taacetic acid), in the zinc (Zn) or calcium (Ca) salt
state, can form stable soluble complexes with a
large number of metal ions. When DTPA releases
its calcium or zinc, it binds to soluble plutonium,
americium, or curium and carries it to the kidneys
where it is then excreted in the urine. The plasma
half-life of CaDTPA is 20-60 minutes. No accu-
mulation of DTPA occurs in tissues or specific
organs. CaDTPA is approximately 10 times more
effective than ZnDTPA for initial chelation of
transuranics. Therefore, CaDTPA should be used
whenever larger body burdens of transuranics are
involved. DTPA has been shown to greatly reduce
the uptake of absorbed plutonium-239 if given
within an hour of contamination. The most effec-
tive dose schedules have not been determined. As
with most chelators, it is more effective when it
is given earlier. Both salts can be given intra-
venously or as a nasal inhalant. Dose recommen-
dations are, for adults, 1 g in 100-250 cc of normal
saline infused intravenously over 3-4 minutes and
repeated on 5 successive days per week. Given
through the aerosolized route, 1 g in a 4 cc vial
is placed in a nebulizer, and the entire volume
is inhaled over 3-4 minutes and repeated daily.
DTPA is distributed by Oak Ridge Associate
Universities under contract with the U.S. Depart-
ment of Energy as an investigational new drug.
The initial care of radiologic casualties with
moderate and severe radiation exposure should
include early measures to reduce pathogen acqui-
sition. These could include low-microbial-content
food, clean water supplies, frequent hand washing,
and air filtration. When possible, oral feeding is
preferred to intravenous feeding to maintain the
immunologic and physiologic integrity of the gut.
During the neutropenic phase of the radia-
tion syndrome, the prevention and management
of infection is the mainstay of therapy. These
patients should be treated with a hospitals standard
regimen for neutropenic patients [6-8]. Empirical
content is suitable. Potassium perchlorate (200mg
by mouth daily) may be given to individuals who
are sensitive to iodine.
5.3.3 Mobilizing Agents
Mobilizing agents are compounds that increase the
metabolic rate of internal contaminants, resulting
in an increase in elimination. Examples of mobi-
lizing agents are the anti-thyroid medications
propylthiouracil, methimazole, and potassium thio-
cyanate. These medications reduce the manufac-
ture of thyroid hormone (T3 and T4) reduce the
presence of radioactive iodine in this critical organ.
Iodine, which has not been oxidized and incorpo-
rated into thyroid hormone, is excreted at a much
faster rate. However, the toxicity of these three
anti-thyroid drugs and the relative ineffectiveness
make them less appealing for use than potassium
iodide.
Ammonium chloride, an acidifying salt given
orally, mobilizes strontium frombody tissues and, if
given with calcium gluconate intravenously, causes
a 40-75per cent decrease inbody stores of strontium
over a period of 3-6 days. The combined treat-
ment is most effective if given early after strontium
deposition, but some effectiveness is still demon-
strated if given as late as 2 weeks after deposition.
Diuretics are known to decrease sodium, potas-
sium, and chloride serum levels. In theory,
diuretics may be useful in reducing sodium-22,
sodium-24, potassium-42, and tritium levels.
Chelators are mobilizing agents that enhance the
elimination of metals from critical organs. Chela-
tors are organic compounds (ligands) that exchange
less firmly bonded ions for metal ions. The kidney
then excretes the stable chelator-metal complex.
Chelation therapy has been used for lead, mercury,
arsenic, and other heavy metals. New chelators,
including DMSA (meso-2,3,-dimercaptosurrinic
acid) for lead toxicity and DMPS (2,3 dimercapto-
1-propanesulfonic acid) for mercury toxicity, have
not been used for metals, including plutonium and
americium.
One of the older chelators, CaEDTA (calcium
ethylenediaminetetraacetate), was used extensively
in the past to treat lead intoxication, and it has
