carbon monoxide poisoning Flashcards
(18 cards)
physical properties of CO:
colourless
odourless
non-irritating gas
how is CO formed?
by incomplete combustion of carbon containing fossil fuels due to incomplete oxidation to carbon dioxide
normal atmospheric conc and lethal conc?
NA = >0.001%
lethal = 0.1%
what can low levels of CO induce?
4
inflammation
apoptosis
cell proliferation
up regulates mitochondrial bio genesis
CO poisoning can be…
acute
subacute
chronic
where does absorption of CO occur?
occurs between airways and red blood cell haemoglobin
CO can be in gas (alveoli) or liquid (air-blood interface) phase
mechanism of CO poisoning:
oxygen and CO are inhaled
they enter blood
CO diffuses into red blood cells = poisoning
what is the CO affinity for Hb compared to oxygen?
245 times greater than that for oxygen
mechanism of CO to CO2:
catalysed by?
catalysed by reduced cytochrome oxidase C in the mitochondria
dependent on O2 availability
common symptoms of mild CO poisoning:
headache
dizziness
nausea and vomiting
tiredness and confusion
stomach pain
difficulty breathing
symptoms of prolonged exposure to CO:
impaired mental state
vertigo
loss of co-ordination
tachycardia
chest pain (angina / heart attack)
seizures
loss of consciousness
what is the mechanism of CO toxicity?
what does CO bind to?
formation of carboxyhemoglobin (COHb)
this impairs delivery of oxygen to body cells = hypoxia
CO binds to intracellular myoglobin and impairs O2 supply to the mitochondria
pathophysiology of CO poisoning:
alters…
release…
CO alters the mitochondrial respiratory chain at the cytochrome c oxidase level
CO and cGMP causes release of nitric oxide from platelets and vascular endothelium
effects on cardiac muscle:
endothelial dysfunction amplifies cardiac vasoconstriction
increases cardiac function and contractility
neurological changes following CO poisoning:
facilitated leucocyte adhesion
release of destructive enzymes
other effects of CO poisoning:
rhabdomyolysis
pulmonary oedema
multi-organ failure
DIC
renal failure
fetal susceptibility:
CO levels in fetus’ can reach up to 10-15% higher than levels in maternal plasma
HbF binds CO 2/3x greater than HbA
elimination half life = 2 hrs for mum, 7 hrs for foetus
dissociation of COHb with different oxygen regimes:
the COHb half-life?
atmospheric O2 = 250 mins
normobaric O2 = 50 mins
hyperbaric O2 = 22 mins
