This is driving me crazy.. Hemoglobin

[MangoPlant]

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Apparently bleeding causes a decrease in the concentration of hemoglobin in the blood. (ex: someone who is not bleeding will have a hemoglobin level of 14g/decileter whereas someone who is bleeding will have 8g/decileter.)

Why does bleeding lower hemoglobin CONCENTRATION. Shouldn't the concentration remain constant even if there is bleeding? I can see how it lowers the TOTAL AMOUNT of hemoglobin in the body, but I fail to see how it lowers the concentration of hemoglobin in blood. The only way is if the blood that is being bled out is a higher concentration of hemoglobin than normal blood in the body.

Anyone have any ideas?

 

[dsoz]

Apparently bleeding causes a decrease in the concentration of hemoglobin in the blood. (ex: someone who is not bleeding will have a hemoglobin level of 14g/decileter whereas someone who is bleeding will have 8g/decileter.)

Why does bleeding lower hemoglobin CONCENTRATION. Shouldn't the concentration remain constant even if there is bleeding? I can see how it lowers the TOTAL AMOUNT of hemoglobin in the body, but I fail to see how it lowers the concentration of hemoglobin in blood. The only way is if the blood that is being bled out is a higher concentration of hemoglobin than normal blood in the body.

Anyone have any ideas?

Maybe blood volume is made up by lymph and interstitial fluid. But hemoglobin takes a little bit of time to be produced.

dsoz

 

[LoLCareerGoals]

Yep, read this on some health site:

"Whenever blood is lost, so are red blood cells, which take 120 days to be formed. Blood volume is replaced more quickly than red blood cells, leading to a lower concentration of hemoglobin."

There is also a related article on slightly different physiology:
http://en.wikipedia.org/wiki/Vampire_%28Blade%29
"Vampire blood cells cannot produce hemoglobin which is why vampires must feed on blood (preferably human) in order to be sustained and nourished. "
I guess it makes sense why blood is "less delicious" to them after some time in the feeding process. Must have to do with progressively lower hemaglobin levels caused by bleeding.

​

 

[theCLE]

I agree with the above statement. Hence, this is why marathon runners and the like are not suggested to give blood because they will have lower levels of oxygen running (and therefore lower levels of hemoglobin, the oxygen carrier)

 

[MedPR]

I agree with the above statement. Hence, this is why marathon runners and the like are not suggested to give blood because they will have lower levels of oxygen running (and therefore lower levels of hemoglobin, the oxygen carrier)

This only supports lower levels of Hb.. Not lower [Hb]. Bleeding causes a decrease in [Hb] because you're losing more RBCs than you are making. RBCs hold tons of Hb so losing 1 RBC means losing many Hb.

 

[Leonardo Noto]

Apparently bleeding causes a decrease in the concentration of hemoglobin in the blood. (ex: someone who is not bleeding will have a hemoglobin level of 14g/decileter whereas someone who is bleeding will have 8g/decileter.)

Why does bleeding lower hemoglobin CONCENTRATION. Shouldn't the concentration remain constant even if there is bleeding? I can see how it lowers the TOTAL AMOUNT of hemoglobin in the body, but I fail to see how it lowers the concentration of hemoglobin in blood. The only way is if the blood that is being bled out is a higher concentration of hemoglobin than normal blood in the body.

Anyone have any ideas?

Yeah, like the other folks said (and you suspected) it's b/c fluid shifts from other compartments of the body recover blood volume fairly quickly but it takes much longer for your body to make new red cells to replace the ones you lost. As an aside, a person who is acutely bleeding in front of you may have a totally normal hemoglobin on labs b/c it takes a little while for the fluid shifts to dilute the red cells that are left in your blood. Very acute bleeders tend to have normal hemoglobin levels whereas subacute/chronic bleeders will have a low hemoglobin b/c there has been time for fluid shifts in the body to recover some of the blood volume (but with fluid, not with many new red cells yet). This was a very clever question, btw. You're going to enjoy physiology in medical school and your internal medicine/ICU rotations.

Dr. Leonardo Noto
www.leonardonoto.com or follow me on Twitter @DrLeonardoNoto

 

[MangoPlant]

Thanks everyone!

 

[theCLE]

I'm confused, as bleeding would decrease the concentration of Hb, so would giving blood. they are the same thing, basically, right?.... or wait, are you saying including oxygen in the mix is invalidating it? why is my statement wrong? If they lose blood for whatever reason, they will have the same blood volume but have less Hb, like you say. The concentration of Hb will be less for the same reason you state. right? thanks for the feedback

 

[Leonardo Noto]

I'm confused, as bleeding would decrease the concentration of Hb, so would giving blood. they are the same thing, basically, right?.... or wait, are you saying including oxygen in the mix is invalidating it? why is my statement wrong? If they lose blood for whatever reason, they will have the same blood volume but have less Hb, like you say. The concentration of Hb will be less for the same reason you state. right? thanks for the feedback

I'm not sure what you're confused about, man. Yeah, if you lose blood (bleeding, donation, hemolysis, whatever) you will end up with a lower hemoglobin concentration after the fluids in your body have a little bit of time to re-equilibrate. Yes, lower hemoglobin --> lower oxygen carrying capacity in the blood so donating blood before a marathon would be a bad idea.

As an aside, the reason why marathoners in the Olympics train at altitude is b/c the hypoxia (due to less oxygen in the air) induces increased red blood cell production (erythopoiesis) --> higher hemoblobin [ ] when they return to sea level which provides a temporary increase in the blood's oxygen carrying capacity (body compensates by decreasing red blood cell production once you return to sea level but it takes awhile for the levels of hemoglobin to decrease from the higher concentration that was appropriate when at altitude). Athletes who cheat use erythropoietin (EPO), a hormone produced by the kidneys that induces erythropoiesis to increase their hemoglobin concentration before a race. Another trick they have is to get blood transfusions before a race, both of which are very dangerous b/c extremely high red blood cell/hemoglobin concentrations in the blood predispose you to blood clots (thromboembolic disease).

Dr. Leonardo Noto
www.leonardonoto.com or follow me on Twitter @DrLeonardoNoto

 

[Leonardo Noto]

Maybe blood volume is made up by lymph and interstitial fluid. But hemoglobin takes a little bit of time to be produced.

dsoz

Great quote (and even greater cartoon)!

Dr. Leonardo Noto
www.leonardonoto.com