Industrial Toxins Cyanide

Question 1

Mechanism of action of cyanide

Answer 1

binding with very high affinity to the ferric ion cytochrome a3 portion of cytochrome oxidase within the mitochondria

Question 2

Cyanide binds with very high affinity to the ferric ion cytochrome a3 portion of cytochrome oxidase within the mitochondria, resulting in what?

Answer 2

abrupt cessation of electron transport and oxidative phosphorylation, thus inhibiting aerobic metabolism

Question 3

primary mechanism for detoxification of cyanide is

Answer 3

its metabolism in the liver by rhodanese to thiocyanate, a nontoxic compound that is renally excreted

Question 4

True or false

The onset of symptoms following inhalational exposure to hydrogen cyanide gas is immediate

Answer 4

True

Question 5

Exposure to concentrations <50 parts per million causes the following symptoms

Answer 5

restlessness, anxiety, palpitations, dyspnea, and headache

Question 6

Higher concentrations of hydrogen cyanide gas cause the following symptoms

Answer 6

severe dyspnea, loss of consciousness, seizures, and cardiac dysrhythmias

Question 7

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

Answer 7

200 parts per million

600 to 700 parts per million

Question 8

median lethal dose of potassium or sodium cyanide in an untreated adult is estimated at _____________

Answer 8

140 to 250 milligrams

Question 9

Describe the typical seriously poisoned patient

Answer 9

altered level of consciousness and is hyperventilating, hypotensive, and bradycardic

Question 10

True or false

patient is not initially cyanotic, as cyanide does not significantly alter the oxygen-carrying capacity of hemoglobin

Answer 10

True

Question 11

The cherry-red skin color is attributed to

Answer 11

increased venous hemoglobin oxygen saturation

Question 12

________________is a consistent clinical feature

Answer 12

Severe unexplained metabolic acidosis

Question 13

Symptoms of poisoning are delayed

Since they require metabolic activation to release free cyanide

Answer 13

1. acetonitrile, a solvent sold commercially as a cosmetic nail remover
2. amygdalin from apricot pits.
3. sodium nitroprusside, which is increased by exposure to sunlight,

Question 14

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

Answer 14

hydroxocobalamin

Question 15

Who should be empirically treated with hydroxocobalamin or thiosulfate?

Answer 15

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.

Question 16

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

Answer 16

Hydroxocobalamin (vitamin B12a)

Question 17

The dose of hydroxocobalamin in an adult patient is

Answer 17

5 grams IV over 15 minutes

Question 18

Hydroxocobalamin has a low toxicity profile; side effects include

Answer 18

transient hypertension, a reddish discoloration of the skin and mucous membranes, and rare anaphylactic reactions

Question 19

antidotes contained in the cyanide treatment kit include

Answer 19

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)

Question 20

True or false

amyl nitrite is not needed when sodium nitrite can be given IV

Answer 20

True

Question 21

The rationale for using nitrites is based on

Answer 21

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

Question 22

Nitrites do have significant side effects, including

Answer 22

hypotension and the development of excessive methemoglobinemia, which will further decrease oxygen delivery with concomitant carbon monoxide poisoning.

Question 23

_______________, 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

Answer 23

Sodium thiosulfate