Page 113 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

80 SECTION | I General

VetBooks.ir Treatment agents (e.g., VX). The phosgene oxime will cause skin
damage which will increase the dermal absorption of the
There is no antidote for phosgene oxime exposure. Move
second agent.
animals into fresh air. Emesis is not recommended after
oral ingestion because of the irritant and corrosive effects
of phosgene oxime. Immediately dilute oral ingestions CYANIDE AND HYDROGEN CYANIDE
with milk or water. Activated charcoal is also not recom-
mended after ingestion, since the primary toxicity is Background
expected to be a local corrosive injury.
Flush eyes with tepid water until pH returns to neutral- Cyanide and related compounds are classified as blood
ity and remains so for 30 min after irrigation is discontin- agents. Cyanogen and cyanogen halides (cyanogen bro-
ued (Brodovsky et al., 2000). Decontamination after mide, cyanogen chloride, cyanogen iodide) have been
ocular exposure is critical since phosgene oxime is used historically as military chemical warfare agents
(ACGIH, 2005). Today cyanide is most likely to be used
absorbed within seconds. Corneal ulcers should be treated
for a terrorist weapon in the form of hydrogen cyanide or
with mydriatic cycloplegiecs to prevent synechiae devel-
cyanogen chloride.
opment (Grant and Schuman, 1993; Brodovsky et al.,
Hydrogen cyanide (Agent AC, HCN, prussic acid) is a
2000). For more severe corneal lesions, topical steroids,
colorless gas with a faint bitter almond-like odor
citrate, ascorbate, and tetracycline or doxycycline may be
used to aid in reepithelialization. (ACGIH, 2005). Hydrocyanic acid is the liquefied form
The skin should be flushed with large volumes of of hydrogen cyanide (Lewis, 2000). Cyanogen chloride
water and mild soap. As phosgene oxime reacts so (Agent CK, ClCN) is either a colorless irritant gas or
quickly with tissue, decontamination is not expected to be liquid with a pungent odor. It was developed to be slightly
entirely effective after pain has been produced. Isotonic heavier than air and to have greater environmental persis-
sodium bicarbonate or 0.5% hypochlorite may remove tence. It can release hydrogen chloride and hydrogen
phosgene oxime that has not yet reacted with tissue. cyanide when it contacts water, acids, or by thermal
Ulcerated skin lesions should be treated just like a thermal decomposition. The water soluble salt forms (calcium
burn. Topical silver sulfadiazine is recommended cyanide, sodium cyanide, and potassium cyanide) will
(Roberts, 1988). Healing of dermal lesions can take from form HCN gas when mixed with a strong acid.
1 month to over a year (Sidell et al., 1997). Both sheep Animals with cyanide poisoning may have an odor of
and horses should receive tetanus prophylaxis. Other spe- bitter almonds in their gastric or ruminal contents or
cies should be vaccinated at the veterinarian’s discretion. expired breath. The ability to smell the bitter almond-like
Large amounts of opioid analgesics may be needed to odor of cyanide is genetically determined, and 20% 60%
help control pain. of the population cannot detect its presence (Hall and
Monitor arterial blood gases, pulse oximetry, and tho- Rumack, 1986).
racic radiographs in patients following significant expo-
sures. Noncardiogenic pulmonary edema may take
12 24 h to develop. If dyspnea develops, administer Pharmacokinetics/Toxicokinetics
100% humidified oxygen, perform endotracheal intuba-
Cyanide and hydrogen cyanide can be absorbed by inhala-
tion, and provide assisted ventilation as required. Beta
tion, ingestion, ocularly and through intact skin (Hall and
adrenergic agonists may help if bronchospasm develops.
Rumack, 1986). Cyanide rapidly diffuses into tissues and
Administer IV fluids but ensure that the animal does not
irreversibily binds to its target sites. Dermal absorption of
become overhydrated (Hoffman, 2002).
significant amounts of hydrogen cyanide gas has not been
reported. There have been no reports of systemic poison-
ing in humans ocularly exposed to cyanide; however, rab-
Concluding Remarks
bits have died following ocular exposure to NaCN, KCN,
Phosgene oxime is considered nonpersistent in the envi- and HCN.
ronment. It hydrolyzes rapidly in aqueous alkaline solu- Cyanide is distributed to all organs and tissues. The
tions. The potential for secondary contamination is high. concentration of cyanide in red cells is greater than that in
Veterinary personnel should wear aprons, rubber gloves, plasma by a factor of two or three (HSDB, 2005).
and masks when treating decontaminated patients to avoid Cyanide accumulates in neural tissue. It preferentially
self-contamination. Phosgene oxime is of interest to ter- accumulates in the hypothalamus, with levels about 40%
rorists, as it penetrates garments and rubber much more higher compared to the hippocampus, cerebellum, and
quickly than other chemical warfare agents. Phosgene cortex (Borowitz et al., 1994). In acute cyanide intoxica-
oxime can also be mixed with other chemical warfare tion, there are no specific pathologic changes.