Cyanide

Question 1

What is the first antidote for cyanide toxicity?

Answer 1

Hydroxycobalamin

Hydroxycobalamin is a form of vitamin B12 that binds to cyanide, forming a non-toxic complex.

Question 2

Why does cyanide cause toxicity?

Answer 2

Cyanide allows adequate oxygenation of haemaglobin but it uncouples oxidative phosphorylation causing tissue hypoxia

Question 3

What disturbance could be shown on ABG?

Answer 3

HAGMA (Classically)

If GCS reduced +/- resp depression then may get mixed resp acidosis

Question 4

What is the oxygen saturation gap?

Answer 4

It is the difference between oximetry oxygen saturations and measured PaO2 on a blood gas machine
A difference of >5% can be caused by a haemoglobinopathy:
Cyanide
Methaemagolbinaemia
Sulfhaemoglobinaemia

An oxygen saturation in the 80s should not generally cause a perioral/oral cyanosis (usually it must be substantially lower before cyanosis occurs). Thus, any time a patient has a clinical cyanosis with an oxygen saturation in the 80s, this suggests methemoglobinemia.

Question 5

What is the mechanism of action of Hydroxycobalamin?

Answer 5

Chelates vascular cyanide

This mechanism helps to detoxify cyanide by forming a stable complex that can be excreted by the kidneys.

Question 6

What is one disadvantage of using Hydroxycobalamin?

Answer 6

Turns skin orange

This side effect can be concerning for patients and may affect the visual assessment of the patient’s skin.

Question 7

What is the second antidote for cyanide toxicity?

Answer 7

Sodium thiosulfate

12.5grams over 10 minutes

Question 8

What is the mechanism of action of Sodium thiosulfate?

Answer 8

Sulfur donor to endogenous rhodanese enzymes

This action helps to facilitate the conversion of cyanide to thiocyanate, which is less toxic and can be excreted by the body.

Question 9

What is one disadvantage of using Sodium thiosulfate?

Answer 9

Need second IV to give it (complexes with hydroxycobalamin)

This requirement complicates treatment logistics and may delay administration.

Question 10

What is the third antidote for cyanide toxicity?

Answer 10

Amyl nitrite

Amyl nitrite is a volatile compound that can be inhaled for quick action in cyanide poisoning.

Question 11

What is the mechanism of action of Amyl nitrite?

Answer 11

Converts Hb to methHb which binds cyanide

Methhemoglobin can bind to cyanide, reducing its availability to interfere with cellular respiration.

Question 12

What is one disadvantage of using Amyl nitrite?

Answer 12

Unconscious pt may not be able to inhale it

This limits its effectiveness in patients who are unable to self-administer the antidote.