ABG Review
1.
Assess O2 (normal: 80-100 for arterial blood*)  Does the client have hypoxemia?
2.
Assess for acidosis (pH <7.35) or alkalosis (pH >7.45).
3.
Assess for Respiratory (pCO2) or Metabolic (HCO3) components.
  .
Evaluation
pH
pCO2**
HCO3
Normal***
7.35-7.45
35-45
22-28
Respiratory Acidosis
<7.35
>45
WNL
Respiratoty Alkalosis
>7.45
<35
WNL
Metabolic Acidosis
<7.35
WNL
<22
Metabolic Alkalosis
>7.45
WNL
>28
 .
 .
resp acid
The "Seesaw"
effect
resp alk
Respiratory acidosis
Respiratory
Respiratory alkalosis
 .
metabolic acidosis
The "Elevator"
effect
metabolic alkalosis
Metabolic acidosis
Metabolic
Metabolic alkalosis
4.
Assess for compensation (the body's ability to correct acidosis or alkalosis).   Compensation is present if the pH is normal even though the pCO2 and/or the HCO3 are abnormal.
5.
If compsensation is present, assess which is the primary component causing the imbalance and which is the compensatory component correcting the imbalance.
.
a. Is the pH in the acid range (7.35-7.40) or in the alkaline range (7.41-7.45)?
b. The component in the same direction as the pH is the primary component.
c. The component in the opposite direction as the pH is the compensatory component.
 .
Evaluation
ph
pCO2
HCO3
Compensated Respiratory Acidosis
7.35-7.40
>45
>28
Compensated Respiratoty Alkalosis
7.41-7.45
<35
<22
Compensated Metabolic Acidosis
7.35-7.40
<35
<22
Compensated Metabolic Alkalosis
7.41-7.45
>45
>28
 .
*
 Venous and capillary blood gases may be obtained in children if the child does not have an arterial line.  The O2 is lower in these samples and may not accurately reflect the client status.
**
 Venous and capillary CO2 may be higher than arterial and may not accurately reflect the client's status.
***
 Normals are for children and adults.  Different parameters exist for the newborn and premature infant during the first few days of life.
Information compiled by R. Davies and L. Puryear                  06/03               (Graphics © L.Puryear)