ABG Question!!!

Daytonite, BSN, RN · Jan 15, 2009

it's respiratory acidosis. when interpreting abgs, there is a step-by-step process to follow:

check the ph - in this case it is out of whack (normal is 7.35-7.45). it is 7.25, so the patient is in acidosis. there is no compensation. there is only compensation when the ph is normal and the co2 and/or the hco3 are messed up.
check the co2 - co2 is 30 - normal is 35-45 so it is out of whack - if you know nothing else about co2, know that it is the respiratory component of abgs.
check the hc03 - the hco3 is 24 - normal is 21-28 - the hco3 is the metabolic component of abgs and since it is normal the metabolic component is not at issue.
analysis: this patient is in respiratory acidosis. if the hco3 had also been abnormal, you would have used the rome mnemonic to help you interpret the gasses. rome tells us

r

espiratory

o

pposite

ph
elevated
pco2
diminished
=
respiratory alkalosis
ph
diminished
pco2
elevated
=
respiratory acidosis

m

etabolic

e

qual

ph
elevated
hco3
elevated
=
metabolic alkalosis
ph
diminished
hco3
diminished
=
metabolic acidosis

when you have normal ph and abnormal co2 and/or hco3 is when you have partially compensated situations. see the end of this document to determine how to determine those situations are interpreted: arterial blood gases basic principles.doc - guide to assessing blood gasses

for abg tutorials and weblinks to sites with practice problems see post #45 on the pathophysiology/ a & p/ microbiology/ fluid & electrolyte resources sticky thread in this forum (https://allnurses.com/nursing-student-assistance/pathophysiology-p-microbiology-145201.html). the rome mnemonic is also posted on post #24.

Nursey103, ADN, RN · Jan 15, 2009

Ok....I guess since the CO2 is not elevated - it didn't make sense that it's respiratory acidosis......but I understand that the HCO3 (metabolic) was normal. So...it doesn't matter which way the the levels go, if it's messed up and the other is normal (like in this case), it's still respiratory acidosis...?!

Thanks!!

allnurses Guide · Jan 15, 2009

It's a weird question - why is the pH 7.25 if the CO2 is LOW?

Nursey103, ADN, RN · Jan 15, 2009

It was just some questions my instructor was doing on the board! I'm totally confused. I read on one website that if the CO2 is going opposite of the pH (like with the pH being acidotic and the CO2 being alkalotic) - that there was compensation :confused:

I'm totally confused now!

Nursey103, ADN, RN · Jan 15, 2009

Maybe this is just a weird, not applicable-type question! I'm reading up on some ABG websites and this type of question is never a possibility! I took an ABG quiz and got all the answers right so I must be on the right track :confused:

Who knows....thanks for all the info anyways!! :heartbeat

Daytonite, BSN, RN · Jan 15, 2009

it's true that if you are answering questions on a test, yes, co2 and ph levels are inversely elevated. as co2 levels increase, ph usually decreases (acidosis). but when someone is breathing very rapidly and deeply they are also blowing off a lot of co2 and those levels will show a drop in those cases if the abgs are drawn during hyperventilation. something i learned from working a stepdown unit where we had patients on ekg monitors is not to rely solely on the technical readouts. we could see all kinds of stuff on the ekg monitors telling us to expect a patient to be in the throws of dying and yet find them sitting up laughing and visiting with relatives. why? you also have to correlate the test results with the physical signs and symptoms. some things may look like a duck, but they don't always quake like a duck or walk like a duck. they are simply something else.

reading and analyzing abg gas numbers on a piece of paper follows distinct rules. don't try to apply the same textbook logic to them while you are diagnosing them. diagnosing them follows a 1,2,3 sequence much like any procedure. deviate from that sequence and you will diagnose them incorrectly every time. a whacky co2 or hco3 may seem impossible for a patient to achieve, but keep in mind that you are not including the clinical picture (signs and symptoms). you are merely being a non judgmental reader and spitting back a diagnosis. after the diagnosis is given, then you can discuss why the situation could be occurring and what pathophysiology is behind the numbers.

allnurses Guide · Jan 15, 2009

If you were hyperventilating, the pH would rapidly correct. I don't know that I've ever in 12 years seen a blood gas like that.

Soon2BNurse3 - it is only "compensated" if the pH has returned to normal. Sounds like you are on the right track, but if you want more info there is a section here called "the land of abg" that is very good: http://www.realnurseed.com/abg.htm

Daytonite, BSN, RN · Jan 15, 2009

Maybe this is just a weird, not applicable-type question! I'm reading up on some ABG websites and this type of question is never a possibility! I took an ABG quiz and got all the answers right so I must be on the right track
Who knows....thanks for all the info anyways!! :heartbeat

Doesn't matter. Diagnose the numbers. Save the analysis of whether the situation is possible or not for afterwards. Make sure you know the normal levels of pH, CO2 and HCO3 off the top of your head. Know the sequence for determining diagnosis. Know the ROME mnemonic. Then just do problems. With all the practice problems on that post on the sticky thread I listed above there is no reason, after practice, that you should mess up interpreting any ABG results on a test. All the other stuff is pathophysiology (why the CO2 OR HCO3 is elevated or decreased when this or that occurs) that you will need to study.

Nursey103, ADN, RN · Jan 15, 2009

I thought if all the values are abnormal - it's partial compensation and if the pH is normal, then it's full compensation :confused:

We're not doing the path (at this moment) - just learning how to read the basic ABG.

Thanks for all the great tips!!!

Nursey103, ADN, RN · Jan 15, 2009

What's the ROME pneumonic?!? Sounds very familiar - I think I was taught that in a past class!

Daytonite, BSN, RN · Jan 15, 2009

the ph is everything.

if the ph is abnormal you have acidosis or alkalosis.
if the ph is normal and the co2 and hco3 are normal, nothing is wrong, don't go looking for trouble.
if the ph is normal and the co2 and/or hco3 are abnormal there is compensation going on and there is an underlying acidosis or alkalosis problem.