abg analysis

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Permalink Reply by dr t. rajesh patnaik on November 5, 2009 at 4:27pm

ABG made easy.......this is very easy and helpful


Like most people ABG have a first name, a middle name, and a last name.
First Name = compensated/uncompensated.
Middle Name = respiratory/metabolic.
Last Name = acidosis/alkalosis

To know the first name, look at the pH. Remember the normal pH is 7.35 – 7.45.
1. If it is 7.35-7.45 (normal) then her first name is COMPENSATED.
2. If the pH is <7.35 or >7.45--then her first name is UNCOMPENSATED.

Again look at the pH to know the last name.
1. If her pH is < (less than) 7.40; her last name is ACIDOSIS.
2. If her pH is > (greater than) 7.40; her last name is ALKALOSIS.

To know the middle name, First you need to look at the CO2 and HCO3.
(Remember: Normal CO2 = 35-45. Normal HCO3 = 22-26. And also remember that pCO2 is an ACID but HCO3 is not (it’s a BASE)).
1. If the CO2 is <35 or >45--her middle name is RESPIRATORY.
2. If the HCO3 is <22 or >26--her middle name is METABOLIC.

Let’s Practice

A. an ABG with the following numbers:
pH = 7.60 CO2 = 30 HCO3 = 22

1.What is his first name?
(His pH is not in the normal range of 7.35-7.45 so his first name is UNCOMPENSATED.)
2.What is his last name?
(His pH is >7.45 so his last name is ALKALOSIS.)
3.What is his middle name?
(His CO2 is <35 and his HCO3 is normal so his middle name is RESPIRATORY.)

So interpretation is UNCOMPENSATED RESPIRATORY ALKALOSIS.

B. pH = 7.31 CO2 = 50 HCO3 = 25

1.What is his first name?
(His pH is not in the normal range so his first name is UNCOMPENSATED.)
2.What is his last name?
(His pH is <7.35 so his last name is ACIDOSIS.)
3.What is his middle name?
(His CO2 is >45 and his HCO3 is normal so his middle name is RESPIRATORY.)

so interpretation is UNCOMPENSATED RESPIRATORY ACIDOSIS.

C. pH = 7.55 CO2 = 40 HCO3 = 30

1. What is his first name?
(His pH is not in the normal range so his first name is UNCOMPENSATED.)
2.What is his last name?
(His pH is >7.45 so his last name is ALKALOSIS.)
3. What is his middle name?
(His CO2 is normal but his HCO3 is >26 so his middle name is METABOLIC.)

so interpretation is UNCOMPENSATED METABOLIC ALKALOSIS.

D. pH = 7.35 CO2 = 45 HCO3 = 21

1.What is her first name?
(Her pH is normal so her first name is COMPENSATED.)
2.What is her last name?
(Her pH is normal--but it is <7.40. So her last name will be ACIDOSIS.)
3. What is her middle name?
(Her CO2 is normal but her HCO3 is <22. So her middle name is METABOLIC).

so interpretation is COMPENSATED METABOLIC ACIDOSIS.

Remember
1.pH and HCO3 are "kissin’ cousins"--they like to go in the same direction.
2.But CO2 is the "black sheep"--pH runs the opposite direction when it sees him coming.

Therefore:
1.Decreased pH with Decreased HCO3 = ACIDOSIS.
2.Increased pH with Increased HCO3 = ALKALOSIS.
3.Decreased pH with Increased CO2 = ACIDOSIS.
4.Increased pH with Decreased CO2 = ALKALOSIS.

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Permalink Reply by Dr. xee on November 5, 2009 at 4:54pm

step 1
look at PH

(normal PH 7.35-7.45)

<7.35 = Acidosis

step 2
look at CO2

(normal 35-45)

>45 = respiratory acidosis (if normal go to step 3)

step 3
look at HCO3

(normal 22-26)

<22 = metabolic acidosis

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Permalink Reply by Dr. xee on November 5, 2009 at 4:57pm

similarly;

step 1
look at PH

>7.45 =Alkalosis

step 2
look at CO2

<35 = respiratory alkalosis (if normal go to step 3)

step 3
look at HCO3

>26 = metabolic alkalosis

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Permalink Reply by Dr. xee on November 5, 2009 at 4:59pm

this is the simplest concept ya got to know, then there are other things like

compensated,
uncompensated
mixed picture
anion gap metabolic acidosis and
non-anion gap metabolic acidosis

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Permalink Reply by Dr. xee on November 5, 2009 at 5:00pm

and then ya can move to knowing whether it is

acute or
chronic or
acute on chronic

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Permalink Reply by Hasib Iskandar on November 7, 2009 at 11:40am

thanx dr. rajesh n dr. xee 4 ur nice replies.

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Permalink Reply by dr t. rajesh patnaik on November 11, 2009 at 4:48pm

ur welcome.........

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Permalink Reply by dude brandon on November 26, 2009 at 5:39pm

Acid-base balance
Compensation
Oxygenation
Base excess
Anion gap

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