Quote from jennielynn
Call me stupid--but I'm having such a time with determining whether a person is in respiratory or metabolic acidosis/alkalosis based on the ABG levels. I know how to determine the acidosis/ alkalosis part---its the difference between metabolic and respiratory that screws me up. If anyone has any suggestions on how to tell the two apart--please share!!!!
Our critical care instructor is fantastic -- she just recently *refreshed* our memories from med-surg and drummed this into our heads ...
First, look at the pH: normal = 7.35-7.45. 7.35-7.39 has an "acidotic lean", 7.41-7.45 has an "alkalotic lean" and 7.40 is *perfect*.
Next look at the HCO3 (normal = 22-26) and the pCO2 (normal = 35-45). Which one "has the same name" as the pH (acidotic or alkalotic)? If it's the HCO3 then the problem is metabolic, and if it's the pCO2 then the problem is respiratory.
The pH is acidemic, the pCO2 is high (CO2 is acid) and the HCO3 is OK. The pCO2 has the same "name" (problem) as the pH - this is respiratory acidosis.
Since either of these 2 systems (respiratory system & metabolic - kidneys) will try to compensate for failure of the other, the more complicated problems come in when there is full or partial compensation - the pH will return to normal (but w/the acidotic or alkalotic "lean") and the other value will also be out of whack - the key is to see which matches the "lean" of the pH.
We call this the who's your daddy method of ABGs ...
I have a packet with tons of these problems -- if anyone wants a sampler with the answers, just send me a PM.