Tuesday 2 November 2010

MRCP revision battle 40.2: Carbon monoxide poisoning

Carbon monoxide has 200x more affinity for Hb than oxygen
This results in a left shift of the oxygen dissociation curve.



Normal levels of carboxyhaemoglobin are <3% in non-smokers or <10% in smokers.




In terms of carbon monoxide poisoning:
  • 10-30% carboxyhaemoglobin = mild poisoning
  • 30-60% = severe poisoning


Features of carbon monoxide poisoning are vague:
  • 90% have a headache
  • 50% nausea/vomiting
  • 50% vertigo
  • 30% confusion

Patients look pink


Severe CO poisoning can cause:
  • fits
  • coma
  • cardiac arrrest/arrthymias
  • pyrexia
  • muscle necrosis
  • acute renal failure
  • increased reflexes and tone

Treatment is:
  • 100% oxygen
  • hyperbaric oxygen if LOC/pregnant/neuro signs - this decreases the half life from 4 hrs to around 22 minutes.



Next.... some pharmacology with acetylator status