Blood Gas Analysis

Question 1

why is precise regulation of acid/bases needed?

Answer 1

enzyme activity
O2 transport
chemical rxn rate

Question 2

normal blood pH

Answer 2

7.35-7.45

Question 3

acidemia

Answer 3

blood pH <7.35

Question 4

alkalemia

Answer 4

blood pH >7.35

Question 5

acidosis

Answer 5

process that lowers pH

Question 6

alkalosis

Answer 6

process that raises pH

Question 7

3 ways body regulates acids/bases

Answer 7

buffers
pulm excretion of CO2 (mins)
renal elim of acids (days)

Question 8

buffer

Answer 8

substance in a solution that prevents extreme changes in pH

Question 9

buffer equations

Answer 9

henderson hasselbach

pH = pKa + log ( [base]/[conjugate acid])

Question 10

pKa

Answer 10

pH where acid is 50% protonated and 50% deprotonated

Question 11

pKa measures

Answer 11

strength of acid

Question 12

buffers in blood

Answer 12

bicarbonate
hemoglobin buffer system
protein buffer
phosphate
ammonia

Question 13

bicarbonate buffer

Answer 13

CO2 +H2O –> H2CO8 –> H+ + HCO3-

Question 14

bicarbonate rxn speed

Answer 14

slow

Question 15

how does the body speed up the bicarbonate rxn

Answer 15

carbonic anhydrase

Question 16

where is carbonic anhydrase located

Answer 16

endothelium
erythrocytes
kidneys

Question 17

hgb buffer

Answer 17

hgb contains multiple histidines
imidizole size chains
H+ binds to rings
displaces O2

Question 18

hgb buffer depends on what

Answer 18

the bicarb buffer to move CO2 intracellular

Question 19

% of CO2 in blood

Answer 19

70% buffered
23% carbaminohemoglobin (not buffered)
7% CO2 dissolved in plasma (PaCO2)

Question 20

bohr effect

Answer 20

CO2 and H+ effect Hbg affinity for O2

Question 21

high CO2/low pH does what to the Hb-O2 curve

Answer 21

right shift

Question 22

haldane effect

Answer 22

deoxyhemoglobin has 3.5% greater affinity for CO2 than hb
PO2 is low in venous blood
hgb carries more CO2

Question 23

central chemoreceptors

Answer 23

respond to changes in CSF pH
H+ activates chemoreceptors
incr MV

Question 24

MV increases ______ for every _____ increase in CO2

Answer 24

MV increases 1-4L/min for every 1 mmHg increase in PaCO2

Question 25

peripheral chemoreceptros

Answer 25

carotid bodies sensistive to: PaO2 PaCO2 pH arterial perfusion

Question 26

aortic bodies nerve

Answer 26

vaguys

Question 27

carotid bodies

Answer 27

glosopharyngeal

Question 28

renal compensation mechanisms

Answer 28

reabsorption of filtere HCO3- excretion of acids ammonia

Question 29

venous gas pH

Answer 29

0.03-0.04 les than arterial

Question 30

venous pO2

Answer 30

less than PaO2

Question 31

venous gas is used for

Answer 31

trends

Question 32

temperature and solubility relationship

Answer 32

inversely proportional

Question 33

at a lower temp ______ goes into solution

Answer 33

at a lower temp more gas goes into solution

Question 34

alpha stat

Answer 34

measures all blood gases at 37F (raise the temp of the sample)

Question 35

alpha stat pH

Answer 35

try to keep pt at 7.4pH

Question 36

pt vs alpha stat pH

Answer 36

pt pH is higher than the alpha stat will read

Question 37

pH stat

Answer 37

taken at temp of pt

Question 38

pH stat pH

Answer 38

keep pH at 7.4

Question 39

drawing a pH stat from hypothermic pt

Answer 39

add CO2 to mx pH of 7.4

Question 40

lower pH and higher CO2 improve

Answer 40

CV perfusion cerebral O2

Question 41

hypoventilation

Answer 41

increases CO2 increases H+ decreases pH

Question 42

hyperventilation

Answer 42

decreases CO2 decreases H+ increases pH

Question 43

base excess/base deficit

Answer 43

amount of strong acide or strong base required to return 1L of whole blood to pH of 7.4 at a PCO2 of 40 mmHg

Question 44

anion gap

Answer 44

difference between measured cations and measured anions

Question 45

anion gap equation

Answer 45

AG = Na+ - (Cl- + HCO3-)

Question 46

normal anion gap

Answer 46

8-12 mEq/L

Question 47

most common unmeasures anions

Answer 47

lactic acid ketones

Question 48

anion gap step 1

Answer 48

determin oxygenation status PaO2 ~ FiO2*5

Question 49

anion gap step 2

Answer 49

determine alkalemia or acidemia pH

Question 50

anion gap step 3

Answer 50

determine respiratory or metabolic resp: normal PacO2 = 35-45 meta: normal HCO3- = 22-28

Question 51

anion gap step 4 (respiratory origin)

Answer 51

acute respiratory acidosis - pH change 0.08 for every 10 mmHg in PCO2 from 40 chronic - pH change 0.03 for every 10mmHg in PCO2 from 40

Question 52

anion gap step 5 (metabolic)

Answer 52

calculate anion gap AG = Na-(Cl+HCO3) Normal: 8-12

Question 53

anion gap step 6

Answer 53

calculate delta gap (AG - 12) + HCO3- delta gap < 22: concurrent non gap delta gap > 26: concurrent metabolic acidosis

Question 54

anion gap step 7

Answer 54

respiratory compensation? metabolic acidosis - PCO2 = (0.7HCO3)+21 or - PCO2 = (1.5HCO3)+8 (winter formula) PCO2 > PCO2 calculated = concurrent resp acidosis PCO2 < PCO2 calculated = concurrent resp alkalosis