71 Carbon Monoxide poisoning

KYJ 71 - Carbon Monoxide (CO)

In knowing your jargon (KYJ)  blogs we explore commonly heard terms in the clinical environment.  It is ECT4Health's little way of contributing to #FOAMed.

Today, the noxious gas Carbon Monoxide (CO) is our topic.

First a story.  As a kid I was into motocross. I loved bikes and motors and would spend hours tinkering in the shed tuning and playing with my bike. One afternoon in the closed up shed with the bike idling away, I started developing a thumping headache and a sudden burst of dizziness. Not making the connection between a closed up shed and an engine spewing out fumes, I learned the hard way about carbon monoxide and some of the early adverse effects.

CO is a colourless odourless tasteless gas produced when organic matter (carbon fuel) is burned. It is present in all hydrocarbon combustion (diesel, petrol, kerosine,oils), and when natural fibers like wood, paper and cotton burn.

The colour of smoke is deceptive, as smoke contains many gases and particulate matter that gives off colour and odour.  CO is invisible.

CO has a remarkable ability to bind to haemoglobin at the same receptor site as oxygen.  The sinister thing is, CO's affinity to bind to Hb is 240-320 times greater than oxygen.  So if there is even the slightest hint of CO in the air you breathe, it will kick off any oxygen from your red blood cells.

Now CO is able to be measured in blood using a venous or arterial blood gas.  Carboxyhaemoglobin (HbCO) levels are considered abnormal when elevated above 3%.
The average smoker may have a HbCO of 5-10%, and values over 25% are pathological.
At the cellular level CO shuts down a cells energy (ATP) production causing hypoxia, and lactic acidosis.
Headaches, shortened clotting times (note that DVT risk is high in smokers), sleepiness, and alteration in consciousness leading to coma and death by asphyxia.

Being so good at sticking to Hb, CO has a slow half life of about 5 hours, but if the patient is administered 100% oxygen, it can be reduced to under an hour.  It is no surprise then that the treatment for CO poisoning is oxygen therapy .
Initially 100% should be applied on suspicion, and an ABG taken to determine levels.
Always take a Neuro obs baseline, and 12 lead ECG.
If severe, treatment may consider Hyperbaric oxygen therapy.  The standard is 18 meters of pressure for 90 minutes.

Every year many people die from deliberate or accidental exposure to Carbon monoxide.  Suicide intent, building fires, car fires, bush fires and blocked flues in caravans/campers are all common.
Less common causes are the use of paint strippers in poorly ventilated areas (methylene chloride) as the liver metabolises these stripper fumes into CO.
Another cause is poorly maintained air compressors being used to fill SCUBA tanks on dive charter boats.   If the exhaust pipe is downwind of the air intakes on a compressor, then CO is sucked into the intake and compresses CO gas into the Scuba tank.

CO is a dangerous poison, and one that is insideous.  The sad reality is that it is impossible for the victim to know they are dangerously affected, because they just drift off to sleep (or never wake up).