CO2 and hydration

Specialties Emergency

Published

Recently a fellow nurse told me that if someone's CO2 is low it means they are dehydrated. I had never heard this before and was wondering if any of you had, and if so, how the two are related.

just looking at labs, i would say one lab that could help differentiate uncomplicated dehydration from a hypovolemic shock state would be the serum lactate. in addition, abg findings and serum potassium levels will provide us with allot of information. hard to say when the co2 level will change. it does seem to occur more often in the pedi population.

phiposurde, thanks for the good debate.

here is a link to research on etco2 monitoring used to assess the level of acidosis in carpet commandos with gastroenteritis.

great discussion guys!

Specializes in critical care,flight nursing.

"just looking at labs, i would say one lab that could help differentiate uncomplicated dehydration from a hypovolemic shock state would be the serum lactate. in addition, abg findings and serum potassium levels will provide us with allot of information. hard to say when the co2 level will change. it does seem to occur more often in the pedi population. "

*** i found that website

from that website a few point seem to come out:

1)"mild or moderate dehydration can usually be treated very effectively with ort"

2)"severe dehydration is characterized by a state of hypovolemic shock requiring rapid treatment. initial management includes placement of an intravenous or intraosseous line and rapid administration of 20 ml/kg of lactated ringer solution or isotonic sodium chloride solution"

3)"laboratory data are generally not required if the etiology is apparent and mild-to-moderate dehydration is present"

even if they don't answer complety our question. i think we can deduct that mild dehydration not much change would present. moderate to severe we could start seeing change in some of the labs and vitals. severe is to be treated just like shock. a cool question would be to know if by level of change in the co2 we can determine the level of dehydration. another point with the electrolytes and the co2 we could calculate an ion gap. in this case would propably high in 2 ways: lactate and ketones.

"phiposurde, thanks for the good debate."

***welcome and return the same. the pursue of knowledge is an expedition not a competition!8)

"here is a link to research on etco2 monitoring used to assess the level of acidosis in carpet commandos with gastroenteritis."

** i don't work with kids to much, what is carpet commandos?? when i google it, they gave me address of carpet cleaner!lol

A carpet commando is just another name for a kid.

http://www.aemj.org/cgi/content/abstract/9/12/1373

http://pediatrics.aappublications.org/cgi/content/abstract/118/1/260

These are the links to the research.

Specializes in critical care,flight nursing.

A carpet commando is just another name for a kid.

http://www.aemj.org/cgi/content/abstract/9/12/1373

http://pediatrics.aappublications.org/cgi/content/abstract/118/1/260

These are the links to the research.

*** Very interesting, but just to keep that discussion interesting:

"In most cases, metabolic alkalosis is caused by loss of hydrochloric acid (HCl) through the kidney or GI tract, especially due to vomiting........

Respiratory: An increase in blood pH shifts the oxygen-hemoglobin dissociation curve to the left. This creates a tighter bond between hemoglobin and oxygen, causing decreased oxygen delivery to tissues. Hypoxemia is worsened by a compensatory hypoventilation to elevate PCO2. Hypoventilation may be severe enough to cause apnea and respiratory arrest. "

So if somoene is vomiting and only vomiting it can direct to metabolic Alkelemia therefore the CO2 would be elevated not decrease, no??

NB: I am like a Dr. House, I like complicated theory!!LOL

The physiology does support this scenario; however, what do you think of this scenario? I do see metabolic alkalosis in GI patients; however, this seems to be in people who receive ongoing or overaggressive GI suctioning. I think what can happen in the acute situation especially with a kiddo is the following: The person develops an acute illness and severe vomiting. While they do loose some hydrogen ions through vomiting, they end up loosing their circulating volume much faster. They end up developing a metabolic acidosis related to the actual hypovolemia. In addition, with many viral illness comes fever. The increase in temp will cause an increase in metabolic demand and increase in the resp drive. As I understand, in most cases, the acidosis is mild and I would not expect significant shifts in the O2/Hbg curve.

Specializes in Peds ED, Peds Stem Cell Transplant, Peds.

Many years of working in a peds ER, let me say every doc looks at the CO2 when distinguishing how dehydrated a kiddo is.

Specializes in critical care,flight nursing.

Last week I took care of a little lady that a nursing care center send her in pre-renal ARF( creat 580). So she was dehydrated ++ and I look at the CO2. of course, it was low as we spoke before. I just wanted to share and prove that I keep my promises!!:welcome:

Great follow up and thanks for bringing the discussion full circle so to speak.

Let's think about h2o and co2; co2 drops with dehydration while the o2 peels off of co2 to bind with hydrogen to incease the h2o. co2 falls because its comnig apart to keep all of the free hydrogen from building up. Makes real since.

Not exactly.

Venous CO2 (NOT ABG pCO2) = HCO3 (bicarb) if you don't believe then check out the normal value in chemistry panel for CO2 and HCO3 on ABG value (they are the same). Not sure why they ever named it CO2 since it really indicates HCO3 levels. This needs to be taught in more colleges for nurses since it is the ONE way without drawing an ABG to tell if someone is acidotic or alkalotic. This is SUPER important and one of the most important things I have EVER learned in my career. I think it's because of how the HCO3 is broken down, the end results is CO2 (carbonic break down).

LOW CO2 (since it is really bicarb which is alkalotic) means that the person is acidotic. A low venous CO2 can actually mean the person is dehydrated for SURE!

Every teacher across America should be teaching this! It is useful in every medical arena. This could potentially prevent a code from occurring on your shift. I go to codes (on code team) all day long and it is the #1 asked question by me, b/c their CO2 is many times low and they could have been calling it in to Dr's to get help before the code.

SO in chemistry panel:

Low CO2 --> ACIDOSIS (not enough bicarb in blood HCO3, could be sign of dehydration which is only 1 explanation of many).

ABG CO2 is different and is NOT same as venous CO2 from Chem/SMAC panel.

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