Page 115 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

82 SECTION | I General

VetBooks.ir ingestion as the absorption of cyanide is rapid. Flush eyes Concluding Remarks
for at least 15 20 min with tepid water. Wash all contam-
Because HCN is lighter than air, it has a long half-life in
inated animals thoroughly with soap and water.
Monitor blood gases and serum electrolytes. air. However, HCN rapidly disperses and is diluted to
nontoxic concentrations. Cyanide does not concentrate in
Administer 100% humidified oxygen with assisted venti-
soil or plant material but can mix with water. Water con-
lation if needed to maintain an elevated pO 2 . Hyperbaric
verts HCN gas to HCN liquid. Treat contaminated water
oxygen therapy is approved for cyanide poisoning, but
with ozone, hydrogen peroxide, or calcium or sodium
experimental animal studies have been questionable (Way
hypochlorite bleach. The potential for secondary contami-
et al., 1972). For severe acidosis (pH , 7.1) administer
nation of rescue personnel is high. Boots, gloves, goggles,
sodium bicarbonate, but acidosis may be difficult to
full protective clothing, and a self-contained positive pres-
correct prior to administration of antidotes in cyanide
sure breathing apparatus are needed (AAR, 2000).
toxicosis (Hall and Rumack, 1986). Control seizures with
As a chemical warfare agent, cyanide is not easy to
benzodiazepines or barbiturates.
disseminate; however, it is widely available which
Cyanide toxicosis usually occurs and progresses so
increases the chances of its use in terrorist activities
rapidly that treatment is rarely administered soon enough
(Burklow et al., 2003). Cyanide works much better as a
to be effective. Antidotal agents should be used if the
terrorist weapon in an enclosed space.
animal is in respiratory distress or a coma. There are
several different antidotal agents that can be used.
Hydroxocobalamin, a vitamin B 12 precursor, is a cobalt
containing chelator. Hydroxocobalamin reverses cyanide MILITARY NERVE AGENTS
toxicosis by combining with cyanide to form cyanocobal- Background
amin (vitamin B 12 )(Hall and Rumack, 1987). It has been
shown to be effective in treating cyanide-poisoned labora- Military nerve agents are probably the most poisonous of
tory animals and has the advantage of producing neither the known chemical warfare agents and are sufficiently
methemoglobinemia nor hypotension, as sodium nitrite toxic that even a brief exposure may be fatal. They were
does. originally synthesized by the Germans during World War
Another choice for treatment of cyanide poisoning II in search of alternatives to the embargos against insecti-
utilizes several steps. Sodium nitrite is given IV over cidal nicotine. Military nerve agents are rapidly acting,
15 20 min; quick administration can cause hypoten- anticholinesterase organophosphate (OP) compounds, and
sion. Sodium nitrite reacts with hemoglobin in the red are more potent than OP insecticides. Military nerve agents
blood cells forming methemoglobin. The methemoglo- contain a C P bond that is unique and very resistant to
bin will combine with free cyanide to form cyanomethe- hydrolysis, except in highly alkaline solutions. At ambient
moglobin. Follow sodium nitrite with IV administration temperatures, nerve agents are viscous liquids, not gases.
of sodium thiosulfate. Sodium thiosulfate supplies sulfur Military nerve agents are generally divided into “G”
for the rhodanase reaction. Thiocyanate is formed and agents and “V” agents. The “G” agents (tabun, sarin,
excreted in the urine. Oxygen, combined with traditional soman) were developed during World War II and are
nitrite/thiosulfate therapy, provides better results than called “G” agents because they were first synthesized in
thiosulfate alone (Way et al., 1972). It is believed Germany. The “G” agents are very volatile and present a
that oxygen may reverse the cyanide cytochrome vapor hazard. The vapors are more dense than air, thus
oxidase complex and aid in the conversion to thio- they stay close to the ground (Garigan, 1996).
cyanate following thiosulfate administration. Other Tabun (Agent GA, C 5 H 11 N 2 O 2 P) is the easiest of the
chelators such as dicobalt-EDTA (Kelocyanor) and “G” agents to manufacture. It is a fruity-smelling (like
4-dimethylaminophenol hydrochloride (4-DMAP) may bitter almonds) combustible colorless to brownish liquid.
be found in Europe, Australia, and Israel (Hillman Contact with bleaching powder generates cyanogen chlo-
et al., 1974; van Dijk et al., 1986). ride (EPA, 1985b). It may also undergo hydrolysis in the
Animal studies to identify other alternate cyanide anti- presence of acids or water, releasing hydrogen cyanide
dotes have tested alpha-ketoglutaric acid, chlorpromazine, (Munro et al., 1999; Budavari, 2000; HSDB, 2005). Sarin
hydroxylamine, phenoxybenzamine, centrophenoxine, nal- (GB, C 4 H 10 FO 2 P) is a colorless liquid with almost no
oxone hydrochloride, etomidate, para-aminopropiophenone, odor in its pure state (Budavari, 2000). Soman (GD,
and calcium-ion channel blockers (Dubinsky et al., 1984; C 7 H 16 FO 2 P) is a colorless liquid with a fruity or camphor
Leung et al., 1984; Bright and Marrs, 1987; Yamamoto, odor. Soman can release hydrogen fluoride when in con-
1990; Budavari, 2000). These antidotes have shown some tact with acids.
promise in the laboratory setting but have not been tried The “V” agents (“V” for venomous) were developed
during actual poisoning situations. in 1954 in the United Kingdom and are more stable than