ACID-BASE ANALYSIS OF BLOOD GAS VALUES - page 2

INTERPRETING BLOOD GASES

"Interpretation", in this case, means applying a set of rules to a particular set of lab values and coming up with a name for it. It is occasionally misleading for two good reasons:

  • because it is a "snapshot" of blood gas values that may be changing rapidly.
  • Some people have more than one problem and this may complicate the interpretation.
The real diagnosis is made by considering the whole patient.

You can use the acid - base map to help you interpret an ABG by placing the values for pH, CO2 and HCO3 where the numbers belong in the appropriate columns.

Consider the following example:

pH = 7.50

CO2 = 32

HCO3 = 25

blood gas map
Notice that the pH of 7.50 is in the alkalotic range.
The CO2 and HCO3 will tell us why.
The CO2 of 32 is also in the alkalotic range and this tells us that the respiratory system is contributing to this alkalosis.
The HCO3 of 25 is in the normal range of 22 to 26 and is not causing this alkalosis.
This tells us that the cause of this alkalosis is a low CO2 caused by hyperventilation: A RESPIRATORY ALKALOSIS.

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last update: december 1, 1999
© 1996-99 Charles Peshkin / EKG Skillbuilders™