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Co2 in serum= HC02 and Anion gap

Cardiac   (7,060 Views | 9 Replies)

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I think this is confusing and many people I know are reading serum C02 from labs as acidic rather than alkaline. Apparently C02 dissolved in blood serum is the same as HC03. Does everyone agree. Also why don't they just say so in the lab results? How does this reading C02 blood coorespond with Anion Gap? What is the significance of anion gap, especially in cardio?

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delphine22 has 5 years experience and specializes in Quality, Cardiac Stepdown, MICU.

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What? That makes no sense.

Just took a class today on ABGs and the RRT who taught it told me that if I had a CO2 reading from a gas, and one from a chem, use the serum value, it's more accurate. It certainly doesn't correspond to bicarb.

I only watch the gap in DKA. Even if sugars are stabilized, our intensivists often like the gap to be closed, or close to it, before taking them off the drip.

The rest of your questions sound like homework.

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psu_213 has 6 years experience as a BSN, RN and specializes in Emergency, Telemetry, Transplant.

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As far as I know, the only way to tell for sure if the blood is acidic or alkaline (or normal) is from the pH in either an AGB or VBG.

CO2 is converted to carbonic acid in the blood, therefore increased CO2 level lead to increased acidity of the blood [that was the down and dirty version ;)].

And, I agree, the last part sounds a bit homework-ish…it't pretty easy to look up.

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MunoRN has 10 years experience as a RN and specializes in Critical Care.

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Most of the CO2 in your body exists in HCO3 (bicarbonate), which is why metabolic panels often use the two interchangeably. To find the amount that exists as a gas within the body as partial pressure of CO2 then a blood gas analyzer needs to be used.

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MunoRN has 10 years experience as a RN and specializes in Critical Care.

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What? That makes no sense.

Just took a class today on ABGs and the RRT who taught it told me that if I had a CO2 reading from a gas, and one from a chem, use the serum value, it's more accurate. It certainly doesn't correspond to bicarb.

I only watch the gap in DKA. Even if sugars are stabilized, our intensivists often like the gap to be closed, or close to it, before taking them off the drip.

The rest of your questions sound like homework.

The purpose of treating DKA doesn't really have a whole lot to do with normalizing blood sugars, since that's sort of irrelevant to treating DKA even though it's the primary cause of it. The purpose is to resolve acidosis and ketosis, which requires insulin regardless of blood glucose levels, which is why we often intentionally cause blood glucose values to rise (usually by giving IV dextrose) so that we can give sufficient insulin to clear the ketones and normalize the anion gap.

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18 Posts; 1,384 Profile Views

Not homework. No longer in school but I did graduate Magna Cum Laude in the top seven of my class and passed my boards in June with 75 questions. Always did my own homework and continue to work hard and question things on my own time as a nurse. I will get the paper I printed out that says CO2 in serum = HCO3. That's the whole point of me bringing it up here. Because it goes against what we have been taught and are used to.

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18 Posts; 1,384 Profile Views

CO2 blood test: MedlinePlus Medical Encyclopedia

Titled CO2 blood test. Starts off with the following:

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CO2 is carbon dioxide. This article discusses the laboratory test to measures the amount of carbon dioxide in the liquid part of your blood, called the serum.

In the body, most of the CO2 is in the form of a substance called bicarbonate (HCO3-). Therefore, the CO2 blood test is really a measure of your blood bicarbonate level.

Article concludes with: Bicarbonate test; HCO3-; Carbon dioxide test; TCO2; Total CO2; CO2 test - serum

So it seems when CO2 is measured outside of a gas form it is considered HCO3 and levels should be coorelated as such. My whole point in bringing this up because I think many of us may be interpreting the values incorrectly. On our blood tests at work it always shows serum CO2 with normal values listed for what we know to be HCO3 values this is why I went back and double checked the whole thing on my downtime from work. I remember getting confused by this in clinicals and not finding anyone to explain it to me except my big fat diagnostic lab values manual.

I just wanted to bring it up to see what more experienced cardiac nurses thought of this. MunoRN says that CO2 in blood is HCO2 and explains that metabolic panels often use the two interchangeably.

This is a communication forum in wich we try to improve our nursing practice by bringing things to each others attention and/or asking for help. Please don't assume a person questioning something hasn't checked for evidence of the topic posed for discussion. I appreciated all taking time to respond. Thank you.

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18 Posts; 1,384 Profile Views

By the way the whole subject brought up is CO2 levels read from a blood test rather than a CO2 blood gas. CO2 blood gas normal levels are btw 35-45. CO2 serum = (HCO3-) normal readings vary btw 22-26 through 29.

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Wile E Coyote is a ASN, RN and specializes in Critical care.

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The confusion is because of the behavior of CO2 varies between venous and arterial systems. The Haldane effect along with the action of carbonic anhydrase infuences how the CO2 behaves...confusingly similar to the Bohr effect.

Edited by Wile E Coyote

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18 Posts; 1,384 Profile Views

Thank you. So when we read CO2 in blood we are reading how CO2 is acting in venous blood (i assume) and blood gasses are then derived from the artrial blood. I will look up the Haldane effect.

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