Quote from charlieroe
Hello, I'm new to the world of ITU nursing, in fact i've just finished my 5th shift and am really struggling with understanding ABG's. Can anyone help explain what it all means, please keep it simple
****There a technic I saw on a DVD that maybe could help you. It is very simple but don't include everything. As a comparison it would be reading only the rhythm and rate on a 12 lead without Reading all the axis, hemiblock, etcetera. Here goes:
You woke up one day in a new world. In that world everybody have 3 name: a first name, a middle name and a last name. But you are limited in your choice:
for first name you can only choose compensated or uncompensated. Middle name respiratory or metabolic and last name acidosis or alkalosis. So you give birth to a baby, in that land baby have ph on the forehead. When they get born you know there first and last name:
first name, between 7.35-7.45 is compensated otherwise, uncompensated. Then for the last name less then 7.4 acidosis. More then 7.4 Alkalosis. Now you want to know who's the dad of that little one so that you can give him is first name. So you will try to find the dad with the same last name. Remember the other normal CO2:35-45 and HCO3: 22-27/32( in some book). Remember those are text book normal. You have to look the normal with your center. ABG change with altitude.Let do an example:
ph 7.25 co2: 55 and Hco3: 34
so our little baby his first name is uncompensated( less then 7,35) and last name acidosis (less then 7.4). Now for his middle name let see who has the same last name. we have the choice between
Mr. respiratory acidosis( co2 more then 45)
Mr. metabolic alkalosis.( HCO3 more then 27)
So the name of our baby is uncompensated respiratory acidosis.
there an other technique recommended by the ACLS for experienced provider. This one is more complex a little bit. But i find it take in consideration mix metabolic state. It has 6 step:
1) determine if PH normal( between 7,35-7,45), acidotic or alkalosis
2)determine if there hypocarbia( CO2 less the 35) or hypercarbia( CO2 more then 45)
3) 40-Co2( result can be positive or negative)
4) multiple by 0,008
5)add to or subs tract from 7,4
6)if ph greater then the calculated PH there a metabolic alkalosis associated. If it's less ,there a metabolic acidosis associated.
ph 7.30, pco2:80, Po2 58 HCO3:38
4)7,4 - 0.32=7.08
5)metabolic alkalosis associated
6)primary resp acidosis with partial metabolic compensation.
One rule to remember:"compensatory mechanism are unlikely to overcompensate in acid-base abnormalities". Meaning in this case it would be very doubtful that the pt would have retain Co2 to compensate the alkalosis state and therefore transfer to acidosis.
Hope it help.