Acid - Base

Question 1

Normal values for blood pH, PaCO2, PaO2, HCO3, SaO2, Pb, PH20

Answer 1

pH: 7.40
PaCO2: 40 mmHg
PaO2: >90 mmHg
HCO3: 24 mEq/L
SaO2: >95%
Pb: 760 mmHg (sea level)
PH20: 47 mmHg

Question 2

If we get an arterial blood sample, how can we be sure it is actually arterial?

Answer 2

SaO2 in most cases is greater than 90%. Unless it is mixed (arterial and venous)

Question 3

Which value can you used to determine if there is a metabolic acidosis/alkalosis

Answer 3

HCO3

Question 4

What is step one for acid-base value analysis?

Answer 4

Assess origin of blood gas sample (is it arterial or venous or mixed?)

Question 5

Step 2?

Answer 5

Assess oxygen status? PaO2, is hypoxia present?

Question 6

Step 3?

Answer 6

Assess ventilation (PaCO2) Hypo/Hyperventilation

Question 7

If your A-a value is 7 what does this mean?

Answer 7

Normal

Question 8

A-a value of 15?

Answer 8

Still normal

Question 9

A-a value of 26?

Answer 9

likely gas exchange impairment

Question 10

If your patient is on supplemental oxygen how does this change the A-a assessment?

Answer 10

instead do PaO2/%oxygen
room air = 21%
oxygen mask = 40%
Anesthesia = 100%

Question 11

Step 3 and 1/2?

Answer 11

A-a Gradient: A = 150 - (PaCO2/0.8)
Then subtract a - A
(a = PaO2)

Question 12

Step 4?

Answer 12

Acid/base status (pH) and is compensation present? (PaCO2 and HCO3)

Question 13

If a patient has a respiratory acidosis what else should you compare?

Answer 13

Ratio between PaCO2 and PaO2 (should be 1:1)

Question 14

If your PaCO2 is low what is the dx?

Answer 14

Respiratory Alkalosis

Question 15

If your PaCO2 is high what is the dx?

Answer 15

Respiratory Acidosis

Question 16

If your HCO3 is low?

Answer 16

Metabolic Acidosis

Question 17

If your HCO3 is high?

Answer 17

Metabolic Alkalosis

Question 18

If your patient is hypoventilating what additional comparison should you make?

Answer 18

PaCO2 and PaO2, for every increase mmHg in PaCO2 there should be a 1 mmHg loss of PaO2

Question 19

What will the PaCO2 be if the patient is hyperventilating?

Answer 19

PaCO2 will be low

Question 20

What will the PaCO2 be if the patient is hypoventilating?

Answer 20

High

Question 21

Two important Blood acid-base rules:

Answer 21

• The body never fully compensates for primary acid-base disorders
• Effect of hypoventilation on oxygen should be 1:1 if it is the sole cause of hypoxemia