Help with Arterial Blood Gases

[Bluebell.]

Hello all, I need help in understanding this one ABG problem.

For most scenarios, I understand why something is a respiratory or metabolic cause. For the questions that that have both the CO2 and HCO3 going in the same direction, I am still confused.

For example: pH is 7.33, PaCO2 is 34, HCO3 is 27, and PO2 is 96. The answer is Metabolic acidosis; partially compensated.

Why is it a metabolic cause rather than a respiratory cause? Both values of CO2 and HCO3 are technically moving towards "alkaline," so I cannot tell what is causing the acidosis. Also, is it partially compensating b/c the CO2 and bicarb are going in the same direction?

Any help would be greatly appreciated.

[NICU Guy, BSN, RN]

pH is 7.35-7.45 (Acid- Alkaline)

PaCO2 is 35-45 (Alkaline-Acid) Respiratory

HCO3 is 22-26 (Acid- Alkaline) Metabolic

7.33 is acidic

34 is alkaline

27 is alkline

Since 7.33 is acidic, you look for which of the others match. In this case it is HCO3. HCO3 is metabolic, so it would be Metabolic Acidosis. Then look at PaCO2, it is trying to pull the pH back to normal by becoming alkaline but pH is still below 7.35 so it is partially compensating.

[Bluebell.]

Thank you. But since 27 is above the normal limit, why is it acidic? I would think above 26 is alkaline.

[203bravo, MSN, APRN]

HCO3 of 27 is alkaline not acidic.

[203bravo, MSN, APRN]

Metabolic acidosis results from all conditions that decrease the pH of the body fluids below 7.35, with the exception of conditions resulting from altered function of the respiratory system. --> pH 7.33 = acidosis and PaCO2 = 34 basic THUS acidosis is not caused by respiratory then it is metabolic.

If metabolic acidosis persists for many hours and if the kidneys are functional, the kidneys can also help compensate for metabolic acidosis. They begin to secrete hydrogen ions at a greater rate and increase the rate of bicarbonate ion reabsorption. ---> both HCO3 and CO2 are becoming basic to compensate,, but since pH is still acidic it is only partially compensated.

[BostonFNP, APRN]

pH is 7.33 PaCO2 is 34, HCO3 is 27, and PO2 is 96. [/quote']

Simple way: Look at the pH and the PaCO2 and apply ROME.

pH is down and PaCO2 is down is "equal" so metabolic.

[203bravo, MSN, APRN]

Simple way:

Look at the pH and the PaCO2 and apply ROME.

Boston - what exactly is ROME? sounds like an easier way to remember this :)

Thanks

[Bluebell.]

Thanks guys :)

[Bluebell.]

Boston - what exactly is ROME? sounds like an easier way to remember this :)

Thanks

I was just about to ask that as well. I did not learn that in class.

[BostonFNP, APRN]

Boston - what exactly is ROME? sounds like an easier way to remember this :) Thanks

Respiratory opposite metabolic equal is ROME. You can use it to determine the primary cause by looking at the pH and the PaCO2. If they are moving in opposite directions (pH up PaCO2 down or vise-versa) it is respiratory, in the same direction (or equal) it is metabolic.

[203bravo, MSN, APRN]

Respiratory opposite metabolic equal is ROME. You can use it to determine the primary cause by looking at the pH and the PaCO2. If they are moving in opposite directions (pH up PaCO2 down or vise-versa) it is respiratory, in the same direction (or equal) it is metabolic.

Excellent -- thank you ... I like that much better than the silly tic-tac-toe board that everyone tries to teach.. and easier to remember :)

[Bluebell.]

Respiratory opposite metabolic equal is ROME. You can use it to determine the primary cause by looking at the pH and the PaCO2. If they are moving in opposite directions (pH up PaCO2 down or vise-versa) it is respiratory, in the same direction (or equal) it is metabolic.

That is a fantastic way to remember this stuff! Thanks for sharing!