Blood pH

medichopeful

Flight nurse, ground paramedic
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You seem to have picked up some extra fluid somewhere. (H2O) + (CO2) <> (H2CO3) <> (HCO3-) + (H+) would be the result of your equation, and this is commonly used to demonstrate the carbonic-acid-bicarbonate equilibrium. Your equation needs an extra H2O on the left to make it correct and show the 2 equations, although to be honest I'm not sure that for the purposes of your average ambulance driver that it adds any useful info.

I've seen the equation written both ways, your way and mine. The way I wrote it [(H20)+(CO2) <-> (H2CO3)+(H2O) <-> (HCO3-)+(H3O+)] shows that there is extra fluid in the body, shows the role of water, and is not balanced. I see what you mean by saying that I would need an extra H2O on the left, but as this equation is not balanced (it just takes into account the excess fluid in the body), it's actually not necessary. Your way is probably a little bit clearer, because it takes water out of the equation. But the fact of the matter is, the water is still there in yours, you just don't see it in the equation. I hope this makes sense :wacko:
 

MrBrown

Forum Deputy Chief
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Oh bloody hell Brown knew finishing reading that basic chemistry book would be a good idea... where is Mrs Brown when you need her, after all she is the chemistry smartypants at Cassa de Brown.
 

JPINFV

Gadfly
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You seem to have picked up some extra fluid somewhere. (H2O) + (CO2) <> (H2CO3) <> (HCO3-) + (H+) would be the result of your equation, and this is commonly used to demonstrate the carbonic-acid-bicarbonate equilibrium. Your equation needs an extra H2O on the left to make it correct and show the 2 equations, although to be honest I'm not sure that for the purposes of your average ambulance driver that it adds any useful info.

H2O is in excess and H+ vs H3O (hydronium ion) is the same thing as you won't have free hydrogen ions floating around when water is present.
 

Smash

Forum Asst. Chief
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Sorry, I'm probably being a touch pedantic. The first equation is used to show the effect of water on the acid-base and non acid-base equilibrium, but to be correct it should read (2H2O) + (CO2) <> ..... and so on. Otherwise it is mathematically incorrect (biology just being chemistry, chemistry being physics and physics being maths after all :) )
 

Sandog

Forum Asst. Chief
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H2O is in excess and H+ vs H3O (hydronium ion) is the same thing as you won't have free hydrogen ions floating around when water is present.

Now ya done it, I'm gonna have Titration lab nightmares again. Blip, blip... :p
 
OP
mikie

mikie

Forum Lurker
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Paging Einstein!

OK so as I'm reading through this and trying to decipher what you chem whiz'z said (though I did take my fair share of chemistry)...

This is occurring in the capillary beds? Venous system? Diffusing during respiration? ----Ya those are loaded questions, but I'm just trying to understand how Arterial blood and Venous blood have similar pH's. Yes it's obviously complex medicine beyond the SOP for medics, I'm just trying to learn B) and understand how this is possible (on a simpler scale).


Thanks EVERYONE!!
 

Commonsavage

Forum Crew Member
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Great discussion, but....KISS

I think the simple answer to a simple question was lost in the minutea of acid-base explanations, some of which are nothing more than complicated guesswork.
So, I will attempt the simple:
1) pH is a relative measurement of the ratio of hydrogen ions (H+) to hydroxide ions (OH-)
2) the pH scale is 1 to 14. 7 is neutral, in which the ratio of H+ to OH- is 1:1.
Anything below 7 is acid, higher in hydrogen ions. Anything above 7 is basic (alkylotic), higher in hydroxide ions.
3) Venous blood is relatively more acid than arterial blood due to the way in which carbon dioxide is carried in the venous serum, in the form of carbonic acid. The presence of lactic acid or pyruvate has very little to do with it. It is the accumulation of CO2 in the form of carbonic acid that is the major and overriding factor.
What you need to know is that, metabolic and/or respiratory issues that take the human organism outside of the narrow limits of 'normal' pH (7.35 - 7.45) can be critical and can be corrected...within limits. Outside of the correctable limits (6.5 - 7.65), recovery is doubtful. Acidosis is much more prevalent than alkylosis. As one's condition deteriorates, with decreased respiratory status and increased tissue catabolism, one becomes acidic.

That, my friend, is the VERY basic bare bones of pH blood chemistry. I am really sorry that your instructor is so ill educated. Unfortunately, at least in my observations of EMT/Paramedic certification/education programs in this country, we have people placed as instructors in courses about which they know only enough to get in trouble, generate myths, and pass on bad information. By the way, that's pretty much the status of many nursing instructors as well.;)
 
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