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Description:
Hydrogen cyanide is usually included among the CW agents
causing general poisoning. It has been reported that hydrogen cyanide was
used in the Iran-Iraq war, against the Kurds during the 1980's. Hydrogen
cyanide has high toxicity and in sufficient concentrations it rapidly leads
to death. During the Second World War, a form of hydrogen cyanide (Zyklon B)
was used in the Nazi gas chambers. At room temperature, hydrogen cyanide is a
colourless liquid which boils at 26 oC. Its high volatility probably makes
hydrogen cyanide difficult to use in warfare since there are problems in
achieving sufficiently high concentrations outdoors. On the other hand, the
concentration of hydrogen cyanide may rapidly reach lethal levels if it is
released in confined spaces.
Signs and Symptoms:
The most important route of poisoning is through
inhalation. Both gaseous and liquid hydrogen cyanide, as well as cyanide
salts in solution, can be taken up through the skin. The most important toxic
effect of hydrogen cyanide is by inhibiting the metal-containing enzymes. One
such enzyme is cytochromoxidase, containing iron. This enzyme system is
responsible for the energy-providing processes in the cell where oxygen is
utilized, i.e., cell respiration. When cell respiration ceases, it is no
longer possible to maintain normal cell functions, which may lead to cell
mortality. Symptoms of cyanide poisoning vary and depend on, for example,
route of poisoning, total dose and the exposure time. If hydrogen cyanide has
been inhaled, the initial symptoms are restlessness and increased respiratory
rate. Other early symptoms are giddiness, headache, palpitations and
respiratory difficulty. These are later followed by vomiting, convulsions,
respiratory failure and unconsciousness. If the poisoning occurs rapidly,
e.g., as a result of extremely high concentrations in the air, there is no
time for symptoms to develop and exposed persons may then suddenly collapse
and die.
Treatment:
The treatment against cyanide poisoning is based on
encouraging and speeding-up the body's own ability to excrete cyanide and to
bind cyanide in the blood. The enzyme rhodanese is present in the body,
mainly in the liver, and together with sulphur transforms cyanide into
thiocyanate, which is passed out in the urine. By supplying sulphur in the
form of sodium thiosulphate (Na2S2O3) the detoxification can be speeded up.
The cyanide ion has high affinity to trivalent iron (Fe3+). The divalent iron
in blood haemoglobin can be oxidized to trivalent, which leads to the
formation of methaemoglobin which binds cyanide ions. The formation of
methaemoglobin can be achieved by supplying sodium nitrite (NaNO2) or
dimethylaminophenol (DMAP). Cyanide can also be bound by metallic ions
supplied to the blood in suitable form. Among others, cobalt can be supplied
in the form of a cobalt complex or as hydroxycobalamin (vitamin B12). In
cases of poisoning with hydrogen cyanide it is of the utmost importance that
countermeasures are immediately introduced. For this reason, a medical
antidote (PAPP, para-aminopropiophenone) for use as a pretreatment is being
developed in the United Kingdom.
"Fact Sheets on
Chemical Warfare Agents, SDE/SEARO, World Health Organization, New
Delhi, India"
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