Confused on ABG's

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Im a 1st year nursing student, and in Med Surg, and I am completely going out of my mind trying to interpret ABGs can anyone help me! :bugeyes::bluecry1:

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Specializes in med/surg, telemetry, IV therapy, mgmt.

abg interpretation tutorials are listed on this post: https://allnurses.com/forums/2488838-post46.html

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Not sure what all you are having problems with but this site really helped me with the basics. I found it on here so whoever posted it I would also like to thank them.....

http://www.realnurseed.com/abg.htm

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I thought I had acid/base figured out until this semester. Here is a typical lab I see from a BMP.

CO2(TOTAL) 22 LOW Expected Value 23-31 meq/L

This is different from PaCO2? 35-45 is not the expected range? And this CO2 actually measures HC03 (from what I have found reading)? I'm very confused. :)

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Specializes in med/surg, telemetry, IV therapy, mgmt.

a bmp is a basic metabolic panel and comes from venous blood serum. abg's are tested from an arterial blood sample. total co2 in the bmp is part of assessing the electrolytes. my lab reference specifically says that venous samples of co2 are likely to be affected by air and are inaccurate. they should only be used as a rough guide of a patient's acid/base balance. only arterial blood will give an accurate co2 measurement.

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Ok thank you, that helps. I haven't seen any patients so far on med-surg with ABGs, just the basic BMP. Is it more common in critical care?

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Specializes in med/surg, telemetry, IV therapy, mgmt.
Ok thank you, that helps. I haven't seen any patients so far on med-surg with ABGs, just the basic BMP. Is it more common in critical care?

ABGs are done on patients with respiratory and breathing problems.

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Stolen from another thread....

An easy way to remember which is which:

ROME:

Respiratory= Opposite:

- pH is high, PCO2 is down (Alkalosis).

- pH is low, PCO2 is up (Acidosis).

Metabolic= Equal:

- pH is high, HCO3 is high (Alkalosis).

- pH is low, HCO3 is low (Acidosis).

RO means to make it Respiratory - if the pH is higher the PaCO2 should be lower. below 35.

ME means to make it metabolic - if the pH is higher the HCO3 should be higher too. greater than 26.

If you have a rare question where the Ph is normal and you need to know which way the patient is "leaning" you take the pH normals and you split them...so the normal range is 7.35 to 7.45, so if you got a question where it was 7.39, it's going to be leaning toward Acidosis. Your instructor won't give you a 7.40 question!!!

The pH alone tells you if it's Acidosis or Aklkalosis right off the bat...so the only thng you have to calculate is if it's respiratory or metabolic and how it's being compensated for.

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Specializes in Med Surg, LTC, Home Health.

Here is a method taught to me by a great teacher. I have condensed the information, so if you have any questions, feel free to PM me.

First, you already know that the ph of blood is 7.35-7.45. Anything less than 7.35 will be acidosis, and anything above 7.45 will be alkalosis.

PaCO2 (parital pressure of carbon dioxide) 35-45-Think of CO2 as an acid. The higher it is, the more acidic. Since CO2 is removed by the lungs, it is the respiratory component.

HCO3 (bicarbonate) 22-26-Think of HCO3 as a base, or alkalotic. The higher the number, the more alkalotic, and the lower the number, the more acidotic. Since HCO3 is removed by the kidneys, it is the metabolic component.

ph- 7.49

PaCO2- 44

HCO3- 28

To get your answer, pick the component that matches the ph. Since the ph is akalotic, and the HCO3 is alkalotic, your answer is metabolic alkalosis.

ph- 7.32

PaCO2- 47

HCO3- 27

To get your answer, pick the component that matches the ph. Since the ph is acidotic, and the PaCO2 is acidotic, your answer is respiratory acidosis. Had the HCO3 been acidotic as well (

In the problem above notice that the HCO3 has risen above normal. It is adding more base to try and neutralize the acid. Since the ph is still abnormal, this is considered partially compensated respiratory acidosis.

If the HCO3 were normal (22-26), it would be uncompensated.

ph- 7.44

PaCO2- 48

HCO3- 29

The ph is normal, but since the others are not, you look at which way it is leaning. Since the ph is closer to an alkalotic state, and the HCO3 is high, there was initially metabolic alkalosis. PaCO2 has risen to compensate for this, bringing the ph back to normal. Thus you have fully compensated metabolic alkalosis.:)

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