Industrial Toxins Cyanide Flashcards
Mechanism of action of cyanide
binding with very high affinity to the ferric ion cytochrome a3 portion of cytochrome oxidase within the mitochondria
Cyanide binds with very high affinity to the ferric ion cytochrome a3 portion of cytochrome oxidase within the mitochondria, resulting in what?
abrupt cessation of electron transport and oxidative phosphorylation, thus inhibiting aerobic metabolism
primary mechanism for detoxification of cyanide is
its metabolism in the liver by rhodanese to thiocyanate, a nontoxic compound that is renally excreted
True or false
The onset of symptoms following inhalational exposure to hydrogen cyanide gas is immediate
True
Exposure to concentrations <50 parts per million causes the following symptoms
restlessness, anxiety, palpitations, dyspnea, and headache
Higher concentrations of hydrogen cyanide gas cause the following symptoms
severe dyspnea, loss of consciousness, seizures, and cardiac dysrhythmias
The median lethal dose for humans from hydrogen cyanide gas is estimated to be ____________ppm for a 30-minute exposure and _____________ppm for a 5-minute exposure
200 parts per million
600 to 700 parts per million
median lethal dose of potassium or sodium cyanide in an untreated adult is estimated at _____________
140 to 250 milligrams
Describe the typical seriously poisoned patient
altered level of consciousness and is hyperventilating, hypotensive, and bradycardic
True or false
patient is not initially cyanotic, as cyanide does not significantly alter the oxygen-carrying capacity of hemoglobin
True
The cherry-red skin color is attributed to
increased venous hemoglobin oxygen saturation
________________is a consistent clinical feature
Severe unexplained metabolic acidosis
Symptoms of poisoning are delayed
Since they require metabolic activation to release free cyanide
- acetonitrile, a solvent sold commercially as a cosmetic nail remover
- amygdalin from apricot pits.
- sodium nitroprusside, which is increased by exposure to sunlight,
should be considered the first-line therapy in cyanide poisoning if exposure involves fire smoke or any other potential source of concomitant carbon monoxide poisoning
hydroxocobalamin
Who should be empirically treated with hydroxocobalamin or thiosulfate?
Patients who have been exposed to smoke and/or fire and present with a Glasgow Coma Scale score of <10 with signs of end-organ damage (i.e., cardiac arrest, seizures, respiratory distress); a carboxyhemoglobin level >10% and/ or lactate level of >8 mmol/L strengthen this decision.
is a metalloprotein with a cobalt center that binds cyanide, removing it from cytochrome oxidase and forming cyanocobalamin, which is then eliminated via the kidneys
Hydroxocobalamin (vitamin B12a)
The dose of hydroxocobalamin in an adult patient is
5 grams IV over 15 minutes
Hydroxocobalamin has a low toxicity profile; side effects include
transient hypertension, a reddish discoloration of the skin and mucous membranes, and rare anaphylactic reactions
antidotes contained in the cyanide treatment kit include
ampules of amyl nitrite for inhalation, 10-mL vials of 3% sodium nitrite (300 milligrams), and 50-mL vials of 25% sodium thiosulfate (12.5 grams)
True or false
amyl nitrite is not needed when sodium nitrite can be given IV
True
The rationale for using nitrites is based on
ability to form methemoglobin, which binds cyanide more avidly than the ferric iron of
cytochrome oxidase, thus removing cyanide from the cytochrome and
enabling the mitochondria to reactivate electron transport and oxidative metabolism
Nitrites do have significant side effects, including
hypotension and the development of excessive methemoglobinemia, which will further decrease oxygen delivery with concomitant carbon monoxide poisoning.
_______________, given after the administration of sodium nitrite, enhances the activity of the enzyme rhodanese, which catalyzes the transfer of sulfate from sodium thiosulfate to cyanide to form thiocyanate, a less toxic form that is excreted by the kidneys
Sodium thiosulfate
