Blood Gas Analysis

Question 1

What is normal pH range

Answer 1

7.35-7.45

Question 2

What is normal PaCO2

Answer 2

35-45 mmHg

Question 3

What is normal HCO3-

Answer 3

24 +/- 4 mEq/L -> 20-28 mEq/L (sheep higher)

Question 4

What is normal BE

Answer 4

0 +/- 4 mEq/L (sheep higher) -> -4-4

Question 5

What is normal PaO2

Answer 5

> 500 mmHg @ 100% O2 (FiO2 = 1)

Question 6

What is normal PaO2/FiO2 ratio

Answer 6

> 500 mmHg

Question 7

What is normal Lactate

Answer 7

<2 mmol/L (don’t worry until >5)

Question 8

What are the steps to interpret an Arterial Blood Gas

Answer 8

Eval pH
Eval respiratory component
Eval metabolic component
Determine primary disorder(s) & if compensation occurring
Eval PaO2
Eval lactate

Question 9

What are you evaluating pH for?

Answer 9

acidemia or alkalemia

Question 10

what are you evaluating respiratory component for?

Answer 10

acidosis or alkalosis

Question 11

what are you evaluating metabolic component for?

Answer 11

acidosis or alkalosis

Question 12

How do you determine the primary disorder?

Answer 12

look at pH -> determine acidemia or alkalemia and then look at PaCO2 and HCO3- and see which is consistent with the acidemia or alkalemia to determine whether is respiratory (PaCO2) or metabolic (HCO3-)

Question 13

How do you determine the compensatory process (if any)

Answer 13

see if time allows for metabolic compensation (remember takes >6-12 hrs) if primary is respiratory OR if there is respiratory compensation for metabolic primary disorder

Question 14

What does the PaO2 tell you?

Answer 14

if not normal for given FiO2 then determine if V/Q mismatch is occurring (impaired gas exchange)
if V/Q mismatch the MOST probable cause during anesthesia is pulmonary atelectasis d/t lateral recumbency

Question 15

What info does Lactate give you?

Answer 15

whether or not metabolic acidosis is an issue and possible post op ischemic mm injury.