Tuesday, 10 February 2015

Cyanide

There was a chemical incident declared once because the pre-hospital team could smell almonds- they thought cyanide could be involved. Turns out someone had been baking... 

Cyanide is released by the incomplete combustion of nitrogen-containing materials, and metabolised from amygdalin. Amygdalin can be found in the pits of many fruits, such as apricots and papayas and raw nuts.

Cyanide is a colourless gas with a bitter almond smell, detectable by only 40% of people.
http://www.christem.com/storage/cyanide%20mechanism
CN blocks cellular respiration by blocking the cytochromes. Affected cells convert to anaerobic metabolism, and a lactic acidosis results. The CNS and the heart are most sensitive.

Symptoms
Symptoms after exposure to high vapor concentrations may include the following:
Transient hyperpnea and hypertension 15 seconds after inhalation
Loss of consciousness in 30 seconds
Respiratory arrest in 3-5 minutes
Bradycardia, hypotension, and cardiac arrest within 5-8 minutes of exposure

Symptoms after exposure to lower vapor concentrations or after ingestion or liquid exposure may include the following:
Feelings of apprehension or anxiety
Vertigo
Nausea, with or without vomiting
Muscular trembling
Loss of consciousness
Headache
Dyspnea

Patients exposed to cyanogen chloride experience severe eye and mucous membrane irritation.Low-dose exposure results in rhinorrhea, bronchorrhea, and lacrimation. Inhalational exposure results in dyspnea, cough, and chest discomfort. Onset of symptoms after exposure to nitriles (acetonitrile and/or propionitrile) may be significantly delayed.

Physical findings of cyanide exposure are generally nonspecific. They classically have cherry red skin.

Laboratory Investigations
- Normal arterial oxygen tension, high venous oxygen tension = decreased AV difference (<10%)
- High anion gap metabolic acidosis
- Raised lactate

Antidotes

Minimal symptoms that resolve spontaneously need observation only.

Other Factors
- Oxygen
- Consider sodium bicarbonate if severe lactic acidosis
- Treat haemodynamic instability and cerebral oedema






References
http://blog.clinicalmonster.com/2015/02/em-ccm-carbon-monoxide-and-cyanide-poisoning/
https://umem.org/educational_pearls/2675/
http://www.enlightenme.org/knowledge-bank/cempaedia/industrial-chemical-incidents

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