CO poisoning

Question 1

Describe CO.

Answer 1

odorless, tasteless, colorless, nonirritating gas formed by hydrocarbon combustion

atmospheric CO is < 0.001%

Question 2

What is the physiology with CO inhalation?

Answer 2

CO binds to Hb with much greater affinity than O2, forming carboxyhemoglobin (COHb) –> impaired oxygen transport and utilization

Question 3

What are the sources of CO poisoning?

Answer 3

• Smoke from fires
• Faulty heating system
• Poor ventilation for heating devices
• Cars operating in poorly ventilated areas

Question 4

How does the oxygenation curve shift with CO poisoning?

Answer 4

Left - diminished ability of the other 3 oxygen sites in Hb to offload oxygen to tissues

Question 5

What are the clinical features of CO poisoning?

Answer 5

• Headache
• Dizziness
• Malaise
• Nausea
• Confusion
• SOB
• Visual changes

Question 6

How do you diagnose CO poisoning?

Answer 6

• May be informed of high CO levels by fire department at site of fire
  OR
• COHb blood levels (venous) - >3% in non-smokers, >10% in smokers

Question 7

What other investigations should be done in CO poisoning?

Answer 7

• ECG
• Troponin/BNP
• ABG/VBG
• FBS
• Urinalysis
• CXR

Question 8

What is the management of CO poisoning?

Answer 8

• ABCDE approach
• High flow oxygen via nonrebreathing mask
• +/- hydroxycobalamin - to treat co-existent cyanide poisoning
• +/- hyperbaric oxygen therapy - if very high COHb or LOC, severe metabolic acidosis

Question 9

What are the long term complications of CO poisoning?

Answer 9

• neurocognitive impairment from hypoxic-ischaemic brain injury
• myocardial injury may predispose to CVD mortality