Originally Posted by kid_next_door
- Why is there a normal Po2 in Methemoglobinemia, oxidized hemoglobin can't carry o2
- Bicarbonate is used in TCA overdose to prevent arrhythmia
- VF & pulse-less VTach are the only arrhythmias that get un-synchronized cardioversion
- Defibrillation is more important than endotracheal intubation while giving basic life support
- MCC of death in hypothermia is arrhythmia (VTach)
To answer your question about why there is normal Pao2 in Methaemoglobinaemia. To understand this it is important to explain the difference between 2 key concepts---- Pao2 measures the the pressure of oxygen DISSOLVED IN PLASMA while Oxygen saturation is the actual measure of oxygen which is carried by the heamoglobin in the red blood cells.
We breathe in Oxygen in room air which gets into the lungs which has to be dissolved in plasma first(PaO2) before the RBCs then take it up(O2 sats).
If you understand the above, then u can see why Methaemoglobinaemia will have a normal PaO2 and a reduced O2 sats. It has nothing to do with the oxygen dissolved with the plasma and everything to do with Hb which is oxidised so it has a low affinity for O2.
Does this make any sense?