Help..Saunders Question regarding Metabolic Acidosis and Respiratory Acidosis

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Hi. This item is from my Saunders review cd and I was wondering if anyone can explain to me why it's metabolic acidosis and not respiratory acidosis.

The following values were given:

ph 7.30

pco2 32 mmhg

bicarbonate 20 meq/L

It says this is metabolic acidosis.

I'd really appreciate your help, thank you.

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maybe this will help you understand it better

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Specializes in PICU, Sedation/Radiology, PACU.

Try this link for information about how to interpret ABG's.

http://www.ed4nurses.com/resources/1/pdf/ABGebook.pdf

This is a very straightforward ABG interpretation question.

First, decide if it is acidosis or alkalosis by looking at the pH. Normal pH is 7.35-7.45.

Acidosis is less than 7.35

Alkalosis is more than 7.45

The pH in this question is 7.30, which is acidosis.

Then, decide whether it is respiratory or metabolic by looking at which value is deviated in the direction that matches the pH.

CO2 is respiratory

Bicarb (HCO3) is metabolic

Normal CO2 is 35-45

Acidosis is more than 45

Alkalosis is less than 35

The CO2 is 32, which shows alkalosis. This does NOT match the pH, so you can eliminate respiratory.

Normal HCO3 is 22-26

Acidosis is less than 22

Alkalosis is more than 26

The HCO3 is 20, which shows acidosis. This matches the pH (pH is also acidosis) so you know that the gas is metabolic acidosis.

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In my A&P2 class, some of the nursing students said they were taught the acronym ROME: Respiratory Opposite, Metabolic Equal. We know it's acidosis since the pH is low. Then look at the pH (low) and the pcO2 (also low). Since they are both low (i.e equal), it's metabolic.

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Thank you Ashley and RunnerRN2b2014, both of you were very helpful! Thank you!

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Thank you futurelpn2012 for the link, I'm watching it right now :)

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If you forget all that, remember at least the normals, Co2, Bicarb, and pH range and the fact that CO2 acts as an acid and bicarb is a base. I used to write it on the board where the C in CO2 was part of the word ACID, and B is for Base and Bicarb.

Too much CO2 may be accompanied by an increase in bicarb-- that's your body trying to bring the pH back to normal (compensation), but it takes some time for the kidneys to do that.

Too much bicarb is usually accompanied by a rise in CO2, but you are more likely to see a drop in bicarb, for instance, if it's being consumed by other acids (acetylsalicylic ACID (aspirin OD) or diabetic ketoACIDOSIS being the big ones, and less often, lactic ACID from hypoxic tissues). That's why patients with DKA and the others are doing Kussmaul resps, big, deep resps that blow off CO2 really fast (decreasing acid load in the body, compensation again), and they have CO2s that are as low as they can get 'em. This is probably the other reason why compensation happens through the lungs for acidoses-- compensation happens really fast that way, and acidoses are more common anyway.

Isn't physiology COOL! Questions like this are why you learn it. In the immortal words of Lord Peter Wimsey as told by Dorothy Sayre, "And if you have forgotten I shall have to teach you all over again."

Note: to get full impact of this message, it should display in Comic Sans, green. Thank you.

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you welcome, hope it helps ;)

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