Hemoglobin and Dyshemaglobinemias Flashcards
How many molecules of oxygen can bind to a single hemoglobin?
4
What is the main function of hemoglobin?
Transport oxygen from the lungs to the tissues and CO2 from the tissues to the lungs
What is cooperative binding?
the principle that once an oxygen molecule binds to iron in one heme group, it changes the shape of the molecule in such a way that it makes subsequent binding easier
What are the two ways oxygen is carried in the blood?
Dissolved in plasma
Combined with hemoglobin
What is allosteric inhibition in regards to oxygen delivery?
It refers to the property of CO2 and H+ to change the conformation of the heme such that oxygen is unloaded and CO2 is picked up (in the form of H+)
What principle facilitates the movement of oxygen from the RBC to the tissues and CO2 from the tissues to the RBC?
Diffusion
How is carbon dioxide transported in the blood?
- Dissolved in plasma
- Plasma proteins
- Combined with Hb
- As HCO3-
What are the components of total hemoglobin?
HbA-hemoglobin
HHb-deoxyhemoglobin
O2Hb-Oxyhemoglobin
COhB-carboxyhemoglobin
MetHb-methemoglobin
What is SaO2?
SaO2 reflects the percentage of Hb molecules in arterial blood saturated with oxygen
What is SvO2?
SvO2 reflects the percentage of Hb molecules in mixed venous blood saturated with oxygen
What is SpO2?
SpO2 reflects the percentage of Hb molecules in arterial blood saturated with oxygen measured by the pulse oximeter
How can we measure oxygen saturation?
- Portable Pulse oximeter
- Portable Co-oximeter
- Calculate via blood gas analysis machine without a CO-oximeter
- Directly measured via a blood gas with a CO-oximeter
What is the difference between a portable pulse oximeter and portable CO-oximeter?
- A co-oximeter measures the percentage of hemoglobin in the blood that is oxyhemoglobin
- A pulse oximeter measures the functional hemoglobin saturation but cannot determine what the Hgb is saturated with
What are the advantages or pulse oximeters?
- Non-invasive
- Continuous monitoring
- well tolerated
- Cheap
- reduced blood loss
What are the disadvantages of pulse oximeters?
- Can be inaccurate
- Does not distinguish among different types of hemoglobins
- can cause heat blisters with prolonged use
What collection techniques must be followed to ensure accurate co-oximetry results?
- Minimum sample of blood 0.3 ml
- Must be collected in air free heparinized syringe
- Blood must be mixed well
- Blood must have air bubbles removed
- blood must be placed on as as per directed by specific device
What are the indications for CO-oximetry?
- Pt history consistent with toxin exposure
- Hypoxia fails to improve with administration of oxygen
- Discrepancy between the PaO2 on blood gas determination and the oxygen saturation on pulse oximetry
- Clinician has reason to suggest carboxyhemoglinemia or mehemoglobinemia
What is the main difference between blood gas analyzers with CO-oximetry and those without?
CO-oximetry allows for direct measurements of O2Hb, HHb, COHb, MetHb
What is the partial pressure of oxygen in the blood at the P50?
27 mmHg
What is the partial pressure of oxygen in the blood at the P90?
60 mmHg
Describe methemoglobin
Hgb molecule whose iron molecule is in an oxidized state and cannot carry oxygen
What is the level of COhb in healthy non-smoking adults?
<2%
What level of COHb is associated with with severe poisoning?
> 20-25%
What level of COHb is normal in smokers?
3-10%
