Pul 3 - Oxygen and Hemoglobin Flashcards
What is the difference between T form of hemoglobin and R form of hemoglobin?
Called taut form, it has low affinity for oxygen, favoring tissue; delivering oxygen to tissue.
R form is called the relaxed form, it has a high affinity for oxygen.
What is positive cooperativity for hemoglobin?
It means that once hemoglobin is bound to one oxygen, it is more likely to bind to a second oxygen, and so on.
What is the cause of the S (sigmoid) shape of oxygen dissociation curve?
Positive cooperativity of hemoglobin to oxygen.
What favors the T form of hemoglobin?
- CO2
- Hydrogen Ion
- Increased temperature
- 2,3-DPG
What is the component of fetal hemoglobin?
It is made up of 2 alpha globins and 2 gamma globins.
What are some unique properties for fetal hemoglobins?
It has lower affinity for 2,3-DPG and higher affinity for O2.
How do we measure PO2 vs how do we measure hemoglobin saturation?
Partial pressure of oxygen is measured by an arterial blood gas (ABG). We can measure hemoglobin saturation with a pulse oxymeter.
How do we shift the oxygen-hemoglobin dissociation curve to the right?
Everything that that favors the change of hemoglobin to a T form; CO2, increase in 2,3-DPG, H+, Increase in temp.
How do we shift the oxygen-hemoglobin dissociation curve to the left?
Decreasing CO2, decreasing 2,3-DPG, alkalosis, decreasing tempature. Also, fetal hemoglobin is shifted to the left (lower affinity to 2,3-DPG).
What are two form of toxic hemoglobin?
Methemoglobin and carboxyhemoglobin.
What is methemoglobin?
It is the oxydized form of hemoglobin; it has iron in the ferric form (Fe3+: remember that ferric ends in “c”, the third letter of the alphabet). Ferrous is the Fe2+ (change the the last letter “s” in ferrous to a “2”).
What are the structural components of Hemoglobin (HbA)?
It is made up of 2 alpha globins and 2 beta globins; each globin is bound to a heme, making 4 heme oxygen binding site in one hemoglobin.
Methemoglobin has decreased affinity for oxygen but has increased affinity for what substance?
Methemoglobin has an increased affinity for cyanide.
What substance do we use to purposely oxidize hemoglobin to methemoglobin? And in what pathology can we use this to our advantage?
Nitrite and sodium nitrite change hemoglobin to methemoglobin. This can be used as an antidote to cyanide poisoning, so the methemoglobin can circulate in the body, picking up cyanide.
What are the components of a cyanide antidote kit?
- Amyl nitrite (inhaled).
- Sodium nitrite (IV).
Then after some time: - Thiosulfate: it binds to cyanide and forms thyocyanade, which then can be excreted by the kidneys.
What are the causes of methemoglobinemia?
They are caused by drugs.
- Nitrates and nitrites.
- Antimalarial drugs: Chloroquine, primaquine.
- Dapsone.
- Sulfonamides.
- Local anesthetics: lidocaine.
- Metoclopramide.
What is the treatment for methemoglobinemia?
- Methylene blue.
- Vitamin C.
- Cimetidine (Gradually lowers it, so not for acute but people with chronic use of drugs that cause methemoglobinemia).
What is carboxyhemoglobin?
Hemoglobin bound to carbomonoxide. It has an affinity of 250x greater than oxygen.
What does carboxyhemoglobin cause?
Decrease in O2 binding capacity. Causes a leftward shift in O2-hemoglobin dissociation curve.
Why is the use of pulse oxymeter detrimental in the case of carboxyhemoglobin poisoning cases?
Patient can have lots of carboxyhemoglobin but the pulse oxymeter will be normal because it only indicates hemoglobin saturation, not specifically for oxygen.
Which for of hemoglobin has a high affinity for oxygen? Which form has low affinity for oxygen?
R form (relaxed) has high affinity for oxygen while T form (taut) has low affinity for oxygen.
