Help with ABG

Double-Helix, BSN, RN · May 3, 2018

O2 admin may be the percentage of oxygen being administered to the patient. In this case, 21%=room air.

We'd like to hear your thoughts first. What do you think is going on? Is the pH normal, acidic or alkalotic? Is it compensated or uncompensated?

KelRN215, BSN, RN · May 4, 2018

pH is 7.423- what does this mean? Is this normal, acid or alkaline?

pCO2 is 48.4 mmHg- you posted the reference range right next to it, so what is going on here? Is CO2 an acid or a base? What can a CO2 of 48 indicate?

Bicarb is 31.6 mmol/L- again, you posted the reference range, so what is going on? Is Bicard an acid or a base? What can a bicarb of 31 indicate?

Once you answer the above, put the whole picture together.

trev343 · May 4, 2018

Oh I understand those basics lol.

What I don't understand is that there was no oxygen added to the patient, he just came in for an ABG, yet it says there was oxygen admin.

Also, at first look it appears like Metabolic Alkalosis with compensating Respitory Acidosis.

But when calculating for the expected pCO2, the number is expected to be lower.

So it would seem to be co-existing Respiratory Acidosis and Metabolic Alkalosis, NOT a compensation.

thatgirl2478 · May 4, 2018

O2 admin was answered - room air has about 21% oxygen... so yeah he's not 'on oxygen' as in he has no tube to his nose, but if he's breathing, it's room air. If he's not breathing you've got bigger problems!

That said, I'm interested in the high PCo2 & high bicarb levels...with that 'normal' (though creeping in on alkaline) pH.

KelRN215, BSN, RN · May 4, 2018

Oh I understand those basics lol.
What I don't understand is that there was no oxygen added to the patient, he just came in for an ABG, yet it says there was oxygen admin.
Also, at first look it appears like Metabolic Alkalosis with compensating Respitory Acidosis.
But when calculating for the expected pCO2, the number is expected to be lower.
So it would seem to be co-existing Respiratory Acidosis and Metabolic Alkalosis, NOT a compensation.

pH is 7.423- it's normal but pointing more towards alkalosis.

CO2 is 48- it's high and it's an acid. Since the pH is pointing more towards an alkalosis and a high CO2 is an acidosis, this is your compensatory mechanism not your problem.

Bicarb is 31.6- it's high and it's a base.

You are correct, this is a metabolic alkalosis and, with the normal pH, you can tell that it's compensated.

Why would you expect the CO2 to be lower in this scenario? When the CO2 is low, that's an indication of alkalosis (CO2 is an acid, losing acid = alkalosis). The CO2 is high (gaining acid) to compensate for the high Bicarb.

trev343 · May 4, 2018

Expected pCo2 is (.7*HCO3-)+20 plus of minus 5.. The pCO2 is higher than expected so it's a separate resp. acidosis.

Do you know what the cause patients elevated oxygen?

student_B, ADN, RN · May 5, 2018

the â†‘PaCO2 is the respiratory compensation for the metabolic alkalosis; the â†‘PaO2 is a bit puzzling though. Perhaps something like continuous vomiting from an obstruction of the small intestine causing metabolic alkalosis from gastric acid loss and hemoconcentration from fluid loss which might result in â†‘PaO2?

trev343 · May 5, 2018

It's an interesting idea.

But still doesn't acknowledge the fact that pCO2 is to high for Metabolic Alkalosis.

I wonder if the chemoreceptors that sense oxygen, are seeing the elevated pO2 and slowing ventilation to decrease O2 content, and as a side effect if the hypoventilation increasing the pCO2

Esme12, ASN, BSN, RN · May 7, 2018

Welcome to AN! The largest online nursing community!

THis may help you figure it out.

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)

and......ABG tic tac toe......

VickyRN I've attached a "tic-tac-toe" type handout I made for my students when I teach ABG's. Hope this helps
Attached Files
ABG Tic Tac Toe Part 1.doc (52.5 KB, 12964 views)
ABG Tic Tac Toe Part 2.doc (94.0 KB, 7399 views)

I can't seem to paste the link. Here is the thread: https://allnurses.com/nursing-student-assistance/abg-help-821378.html

murseman24, MSN, CRNA · Jul 9, 2018

Hey boss, I think you're overthinking it. Ventilation responds primarily to CO2, and secondarily to PaO2 only when severely hypoxic. The respiratory drive doesn't decrease in response to increased PaO2 in the blood. This is altogether a non-concerning ABG. There are some slight abnormalities, but nothing acute or life threatening. Maybe drugs? diuretics? vomit? who knows? Nothing too worry about.