Question

1. pH 7.44 PaCO2 80 mm Hg HCO3- 30 mEq/L

   	a	metabolic acidosis with partial respiratory compensation
   	b	metabolic alkalosis with partial respiratory compensation
   	c	respiratory alkalosis with full renal compensation
   	d	metabolic alkalosis with full respiratory compensation

2. pH 7.25 PaCO2 40 mm Hg HCO3- 20 mEq/L

   	a	metabolic acidosis with no respiratory compensation
   	b	respiratory acidosis with no renal compensation
   	c	metabolic acidosis with partial respiratory compensation
   	d	respiratory acidosis with partial renal compensation

3. pH 7.31 PaCO2 55 mm Hg HCO3 28 mEq/L

   	a	respiratory acidosis with no renal compensation
   	b	respiratory acidosis with partial renal compensation
   	c	respiratory acidosis with full renal compensation
   	d	respiratory acidosis with no metabolic compensation

4. pH 7.50 PaCO2 35 mm Hg HCO3- 48 mEq/L

   	a	metabolic acidosis with partial respiratory compensation
   	b	metabolic alkalosis with partial respiratory compensation
   	c	metabolic alkalosis with no respiratory compensation
   	d	metabolic alkalosis with no renal compensation

5. pH 7.20 PaCO2 69 mm Hg HCO3 37 mEq/L

   	a	respiratory acidosis with partial renal compensation
   	b	metabolic acidosis with partial respiratory compensation
   	c	metabolic acidosis with no respiratory compensation
   	d	metabolic alkalosis with no renal compensation

Answer 1

1) metabolic alkalosis with complete respiratory compensation

2) metabolic acidosis with no respiratory compensation

3)respiratory acidosis with partial renal compensation

4)metabolic acidosis with no respiratory compensation

5)respiratory acidosis with partial renal compensation

Method of Acid Base Balance Interpretation

Step 1. Use pH to determine Acidosis or Alkalosis.

ph
< 7.35	7.35-7.45	> 7.45
Acidosis	Normal or Compensated	Alkalosis

Step 2. Use PaCO2 to determine respiratory effect.

PaCO2
< 35	35 -45	> 45
Tends toward alkalosis Causes high pH Neutralizes low pH	Normal or Compensated	Tends toward acidosis Causes low pH Neutralizes high pH

Step 3. Assume metabolic cause when respiratory is ruled out.

• You'll be right most of the time if you remember this simple table:

High pH	Low pH
Alkalosis	Acidosis
High PaCO2	Low PaCO2	High PaCO2	Low PaCO2
Metabolic	Respiratory	Respiratory	Metabolic

• If PaCO2 is abnormal and pH is normal, it indicates compensation.
  • pH > 7.4 would be a compensated alkalosis.
  • pH < 7.4 would be a compensated acidosis.

Step 4. Use HC03 to verify metabolic effect

• Normal HCO3- is 22-26

Please note:

• Remember, the first three steps apply to the majority of cases, but do not take into account:
  • the possibility of complete compensation, but those cases are usually less serious, and
  • instances of combined respiratory and metabolic imbalance, but those cases are pretty rare.
    • "Combined" disturbance means HCO3- alters the pH in the same direction as the PaCO2.
      • High PaCO2 and low HCO3- (acidosis) or
      • Low PaCO2 and high HCO3- (alkalosis).