Blood Gas Analysis

Question 1

Acid-base homestasis =

Answer 1

maintaining normal H+

Question 2

acid-base homestoasis involves which organs (systems)

Answer 2

lung, kidney, liver, and GI

Question 3

chemical buffers

Answer 3

extracellular: HCO3-; acts within seconds

intracellular: phosphate, proteins; act within hours

Question 4

respiration buffer systemm

Answer 4

adjusting CO2; acts within minutes

respiratory compensation

Question 5

how does the renal system buffer the body

Answer 5

excreting H+, retaining HCO3-

acts within hours - powerful but slow

metabolic compensation

Question 6

Henderson-Hasselbalch equation

Answer 6

pH≈ HCO3- / PaCO2

Question 7

what are the measure vaiables with blood gas analysis

Answer 7

pH

PaCO2

PaO2

Question 8

what variables are calculated with blood gas analysis

Answer 8

HCO3-

BE

oxygen content (CaO2)

Question 9

• emia

Answer 9

changes in blood

Question 10

-osis

Answer 10

physiological processes

Question 11

what variable should be assess respiratory component

Answer 11

PaCO2

Question 12

which variable assess the metabolic component

Answer 12

BE (or HCO3-)

Question 13

T/F there is no time for metabolic compensation during anesthesia

Answer 13

True

Question 14

normal pH

Answer 14

7.35-7.45

Question 15

primary acid-base disorder

Answer 15

the initial change in HCO3- or PaCO2

Question 16

compensation

Answer 16

secondary change in HCO3- or PaCO2 in order to attenuate the effect of the primary disorder on blood pH

no classifed in the terms of acidosis/alkalosis

Question 17

how are mixed acid-base disorders diagnosed

Answer 17

pH value is unexpected from a change in HCO3- or PaCO2

normal pH with abnormal HCO3- or PaCO2

HCO3- and PaCO2 are changing in opposite directions

Question 18

normal HCO3-

Answer 18

24 +/- 4 mEq/L

cats tend to be lower, herbivores tend to be higher

Question 19

normal PaCO2

Answer 19

35-45 mmHg

cats tend to be lower

Question 20

what is base excess

Answer 20

refers to excess or deficit in the amount of base present in the blood

defines the metabolic component of acid-base dustrubances

Question 21

what does a positive BE indicate

Answer 21

metabolic alkalosis

Question 22

what does a negative BE indicate

Answer 22

base deficit - metabolic acidosis

Question 23

what is normal BE

Answer 23

0 +/- 4 mEq/L

Question 24

TCO2 is…

Answer 24

BICARB!

Question 25

PaCO2 is

Answer 25

partial pressure (mmHg) of CO2 in the arterial blood defines alveolar ventilation (CO2 production is normally stable)

Question 26

PaCO2 \> 45

Answer 26

hypercapnia and hypoventilation

Question 27

PaCO2 \< 35

Answer 27

hypocapnia and hyperventilation

Question 28

T/F any combination of RR, tidal volume, or breathing effort can reflect any PaCO2 value

Answer 28

**True**

Question 29

increased PaCO2 will

Answer 29

lower th PAO2 (hypoxemia) -partial pressure of O2 in alveolar space lower the pH refelect respiratory acidosis reflect respiratory compensation for metabolic alkalosis

Question 31

T/F PaO2 does not reflect O2 content and needs to be interpreted in light of FiO2

Answer 31

**True**

Question 32

what is FiO2

Answer 32

inspired O2 fraction at 100% O2 → FiO2 = 1 at air → FiO2 = 0.21

Question 33

lower than expected PaO2 values may indicate

Answer 33

inadequate gas exchange (V/Q mismatch) resulting from pulmonary atelectasis

Question 34

if breathing 100% O2 expect PaO2...

Answer 34

\>500 mmHg

Question 35

if gas exchange was perfect...

Answer 35

PAO2 = PaO2

Question 36

T/F PaO2 is always lower than PAO2

Answer 36

**True**

Question 37

normal values of A-a difference

Answer 37

breathing air → \< 14 mmHg breathing 100% O2 → \<110 mmHg

Question 38

causes for high A-a

Answer 38

V/Q mismatch (#1 cause under anesthesia) right to left shunt diffusion impairment

Question 39

reasons for V/Q mismatch

Answer 39

Atelectasis (common under anesthesia) lung disease

Question 40

when is A-a difference used

Answer 40

clinically to distinguish between lung disease (V/Q mismatch) from hypoventilation as a cause of hypoxemia

Question 41

A-a difference with hypoventillation

Answer 41

normal

Question 42

A-a difference with V/Q mismatch

Answer 42

abnormal

Question 43

PaO2 / FiO2 ratio

Answer 43

same purpose as A-a difference but easier to interpret normal: \>500 mmHg

Question 44

5 causes of hypoxemia (low PaO2)

Answer 44

low FiO2 hypoventilation diffusion impairment V/Q mismatch right to left shunt

Question 45

causes of hypoxia

Answer 45

hypoxemia insuffient tissue perfusion (e.g. low CO) insufficient O2 uptake

Question 46

CaO2 is mostly defined by

Answer 46

[Hb] and SaO2 O2 is carried by Hb

Question 47

T/F while PaO2 is important in diagnosing V/Q mismatch, it has little impact on O2 content

Question 48

high lactate (\>2 mmol/L) may indicate

Answer 48

increased anaerobic metabolism

Question 49

high lactate leads to

Answer 49

increased anaerobic metabolism and produced lactate and acids symptom is called: lactic acidosis

Question 50

lactate can be used as..

Answer 50

a prognostic indicator high lactate level that does not decrease after treament indicates poor prognosis