ABG interpretation help

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:

• ph

  elevated

  pco2

  diminished

  =

  respiratory alkalosis

  
  

• ph

  diminished

  pco2

  elevated

  =

  respiratory acidosis

  
  

• 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