Topic 6B - Alpha stat versus pH stat Flashcards Preview

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Flashcards in Topic 6B - Alpha stat versus pH stat Deck (43):
1

Buffer systems designed to maintain
constant ratio of?

Ratio of [OH-] to [H+] (16:1) despite changes in temperature

Bicarbonate; protein; phosphate

2

Primary blood buffering system
responsible for this maintaining the constant ratio is?

the imidazole moiety of the amino acid histidine

Found on most blood borne proteins

3

HIm+ <> H+ + Im

imidazole

In blood, this dissociation accounts
for most of the changes in pH due to
changes in temperature

4

Alpha stat and pH stat management
ONLY affect control of?

control of the arterial PCO2 and pH

5

How do you correct arterial pO2?

MUST be temperature corrected

6

pH of the blood will ______ with changes in temperature

vary inversely

7

Within body, temperature and pH ____
from organ to organ

will vary

8

Acid-Base balancing system does? (3)

-Maintains constant pH difference across cell membranes
-Maintains constant ratio of negative to positive charges on proteins
-Allows enzyme systems to work at optimal level regardless of temperature

9

pH-stat is what?

-maintain constant pH with change in temperature
-CO2 content has to increase as temperature decreases and has to decrease as temperature increases

10

pH-stat
--- ratio changes ?

ratio of unprotonated histidine imidazole group to H+ (alpha value) changes as CO2 content increases

11

Alpha stat

-maintain constant CO2 content with change in temperature
-pH will increase as temperature decreases and pH will decrease as temperature increased

12

Alpha stat
--- ratio changes how?

ratio of unprotonated histidine imidazole group to H+ (alpha value) remains constant

13

Alpha stat pH will increase as ___

pH will increase as temperature decreases

14

maintain constant CO2 content with change in temperature

Alpha stat

15

-maintain constant pH with change in temperature

pH stat

16

ratio of unprotonated histidine imidazole group to H+ (alpha value) remains constant

Alpha stat

17

ratio of unprotonated histidine imidazole group to H+ (alpha value) changes as CO2 content increases

pH stat

18

pH stat Consequences during hypothermia (5)

*blood more acidic
*hydrogen ion gradient across the cell membrane changes
*acidity alters metabolic activity
*cells do not maintain electroneutrality
*added CO2 influences blood flow regulation

19

pH stat -- as temp decrease how do you maintain "normal" pH

as temperature decreases, CO2 is added to maintain “normal” pH

20

pH stat -- as temp increases how do you maintain "normal" pH

as temperature increases, CO2 must be removed

21

Alpha Stat - as temperature decreases, pH _?

as temperature decreases, pH will rise

22

Alpha Stat - as temperature increases, pH will?

as temperature increases, pH will fall

23

Alpha Stat - Consequences during hypothermia

-maintain constant charge on alpha-imidazole side chain
-hydrogen ion gradient across cell does not change
-cellular enzyme functions are maintained
-cells maintain electroneutrality
-auto-regulation of blood flow maintained

24

maintain constant total CO2 content in the blood

Alpha stat

25

total CO2 content in the blood must increase
-- active addition of CO2
-- alteration of ventilation

pH stat

26

pH-stat shifts oxy-hemoglobin
dissociation curve to ___ which offsets ____

...right which offsets leftward shift due to hypothermia

27

Cerebral Blood flow loses autoregulation when temp falls below?

Loses autoregulation when temperature falls
below 20C

28

When temp falls below 20C - what is the affect on Cerebral Blood Flow ? (2)

-flow becomes pressure dependent
-luxury flow (flow >> metabolic rate)

29

Cerebral Blood Flow
-- pH-stat uncouples what?

flow and metabolism

30

Cerebral Blood Flow
-- Alpha-stat maintains?

maintains autoregulation

31

Cerebral Blood Flow
-- pH-stat uncouples flow and metabolism which means greater bld flow is __ dependent

greater blood flow–pressure dependent

32

Cerebral Blood Flow
-- pH-stat Luxury Flow predisposes what? (3)

-predispose to risk of embolic injury
-high intracranial pressure
-edema

33

Cerebral Blood Flow
- alpha stat lower blood flow–based on?

lower blood flow–based on metabolism

34

Cerebral Blood Flow
- alpha stat predispose to ?

predispose to adverse distribution of blood flow–risk of ischemic injury

35

pH or alpha stat?
PROFOUND ARREST w/ADULTS

Combination (cross-over) best approach–use pH stat while cooling to ensure maximal cerebral metabolic suppression–switch to alpha-stat to remove acidosis

36

pH or alpha stat?
INFANTS

Appears pH-stat may offer better outcomes (major cause of brain injury may relate more to hypoperfusion rather than emboli

37

pH or alpha stat?
REGULAR BYPASS ADULTS: With little or no hypothermia

With little or no hypothermia might not make any difference.

38

pH or alpha stat?
REGULAR BYPASS ADULTS: With mild to moderate hypothermia

With mild to moderate hypothermia alpha-stat might be better

39

keep uncorrected pH and PCO2 values at normal levels (7.4 & 40 mmHg)

Alpha stat

40

keep corrected PCO2 equal to the patient’s
core temperature (i.e. PCO2 will decrease) and corrected pH will increase

Alpha stat

41

Alpha stat - look at which pH and PCO2 values?

uncorrected pH and PCO2 values at normal levels

42

keep corrected pH and PCO2 values at normal levels (7.4 & 40 mmHg)

pH stat

43

pH stat - looks at which pH and PCO2 values?

keep corrected pH and pCO2 values

(uncorrected pH will decrease and the uncorrected PCO2 will increase)