ABG interpretation help

I'MIV · Feb 6, 2008

oops.

Soonstudent · Feb 6, 2008

The first one looks like partially compensated metabolic alkolosis. Your PH is more on the basic side. Your elevated Bicard is causing this. The elevated CO2 is trying to correct this. Don't confuse this with resp failure because the CO2 is high, it's a compesatory mechanism. The PO2 isn't the greatest, but I don't know how much O2 the Pt is on.

On the second one the pt is vented. You've taken out the pt's compesation, causing their PH to rise. Still metabolic alkolosis, thats's the problem. pO2 still not the greatest. what's their FIO2?

Pt with resp failure, acute hemodynamically mediated RF, right sided HF... vented, TPN, dec LOC.
Pt had these values on admission about 6 weeks ago:
pH 7.46 H
pCO2 50.5 H
pO2 71.2 L
HCO3 35.3 H
O2Sat 94.9
So pH, CO2 and HCO3 are all elevated. What is this? A compensated case of what? Other than acidosis d/t the pH, I have no idea.
2 days ago pt was:
pH 7.5 H
pCO2 41.4
pO2 67.8 L
HCO3 31.2 H
O2Sat 94.9
Is this metabolic acidosis even though pCO2 is in the normal range? However in lecture we were told that HF will be metabolic acidosis early and then eventually become respiratory acidosis, is that right?
I am having a hard time interpreting this and figuring out what is expected in this case. I appreciate any input!!

ladybugsea · Feb 6, 2008

Soonstudent, thanks! FiO2 for that draw, I don't know. I've seen 55 and 40, not sure what it was then.

Daytonite, BSN, RN · Feb 6, 2008

pt had these values on admission about 6 weeks ago:

ph 7.46 h (normal 7.35 - 7.45), so patient is in alkalosis

pco2 50.5 h (normal 35 - 45 mm hg), so this is elevated

po2 71.2 l (normal is 80% - 100%)

hco3 35.3 h (normal is 21 - 28 meq/l), so this is elevated

o2sat 94.9 (normal is 95% - 100%), so this is slightly depressed

so ph, co2 and hco3 are all elevated. what is this? a compensated case of what? other than acidosis d/t the ph, i have no idea.

when assessing abgs the three values that are most important to look at are the ph, co2 (carbon dioxide), and hco3 (bicarb). in this first scenario you have the ph elevated, co2 elevated and the hco3 depressed. if you use the rome mnemonic:

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

you will see that with an elevated ph, co2 cannot be elevated. however, with an elevated ph you can have a diminished hco3 which puts this patient in metabolic alkalosis. the elevated co2 levels indicates that the patient is attempting to compensate through his respiratory tract, as carbon dioxide is a gas that is controlled through the respirations.

2 days ago pt was:

ph 7.5 h (normal 7.35 - 7.45), so patient is still in alkalosis

pco2 41.4 (normal 35 - 45 mm hg), so this is normal

po2 67.8 l (normal is 80% - 100%), so this is low

hco3 31.2 h (normal is 21 - 28 meq/l), so this is low

o2sat 94.9 (normal is 95% - 100%), so this is slightly depressed

is this metabolic acidosis even though pco2 is in the normal range? however in lecture we were told that hf will be metabolic acidosis early and then eventually become respiratory acidosis, is that right?

go through the same process of classifying the results. this time you still have a high ph, but look at the co2 and hco3 levels. they are quite different. if you look at the rome mnemonic it now indicates that you cannot have an elevated ph and a low hco3, but you can have a low co2. this patient's co2 is within normal range. however, his ph indicates that he is still in alkalosis and it will be metabolic alkalosis before it becomes respiratory alkalosis because hco3 is part of the body's buffering system. he is still in metabolic alkalosis, but his respiratory status has improved (o2 sat is 94.9%).

there are links and tutorials on abgs that include how to interpret abg results on post #46 of this sticky thread on this student forum:

https://allnurses.com/forums/f205/pathophysiology-p-microbiology-fluid-electrolyte-resources-145201.html

Rnmkonoinmedsurg · Feb 6, 2008

looks as if pt is in metabolic alkalosis, b/c of the elevated pH and bicarb, the pco2 is elevated as well b/c its trying to compendate for the pts alkalosis state.