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Perf Tech II (exam 1) > Topic 6B - Alpha stat versus pH stat > Flashcards

Topic 6B - Alpha stat versus pH stat Flashcards

1
Q

Buffer systems designed to maintain

constant ratio of?

A

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

Bicarbonate; protein; phosphate

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2
Q

Primary blood buffering system

responsible for this maintaining the constant ratio is?

A

the imidazole moiety of the amino acid histidine

Found on most blood borne proteins

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3
Q

HIm+ <> H+ + Im

imidazole

A

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

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4
Q

Alpha stat and pH stat management

ONLY affect control of?

A

control of the arterial PCO2 and pH

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5
Q

How do you correct arterial pO2?

A

MUST be temperature corrected

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6
Q

pH of the blood will ______ with changes in temperature

A

vary inversely

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7
Q

Within body, temperature and pH ____

from organ to organ

A

will vary

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8
Q

Acid-Base balancing system does? (3)

A
  • 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
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9
Q

pH-stat is what?

A
  • maintain constant pH with change in temperature

- CO2 content has to increase as temperature decreases and has to decrease as temperature increases

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10
Q

pH-stat

— ratio changes ?

A

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

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11
Q

Alpha stat

A
  • maintain constant CO2 content with change in temperature

- pH will increase as temperature decreases and pH will decrease as temperature increased

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12
Q

Alpha stat

— ratio changes how?

A

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

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13
Q

Alpha stat pH will increase as ___

A

pH will increase as temperature decreases

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14
Q

maintain constant CO2 content with change in temperature

A

Alpha stat

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15
Q

-maintain constant pH with change in temperature

A

pH stat

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16
Q

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

A

Alpha stat

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17
Q

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

A

pH stat

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18
Q

pH stat Consequences during hypothermia (5)

A
  • 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
Q

pH stat – as temp decrease how do you maintain “normal” pH

A

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

20
Q

pH stat – as temp increases how do you maintain “normal” pH

A

as temperature increases, CO2 must be removed

21
Q

Alpha Stat - as temperature decreases, pH _?

A

as temperature decreases, pH will rise

22
Q

Alpha Stat - as temperature increases, pH will?

A

as temperature increases, pH will fall

23
Q

Alpha Stat - Consequences during hypothermia

A
  • 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
Q

maintain constant total CO2 content in the blood

A

Alpha stat

25
Q

total CO2 content in the blood must increase

    • active addition of CO2
    • alteration of ventilation
A

pH stat

26
Q

pH-stat shifts oxy-hemoglobin

dissociation curve to ___ which offsets ____

A

…right which offsets leftward shift due to hypothermia

27
Q

Cerebral Blood flow loses autoregulation when temp falls below?

A

Loses autoregulation when temperature falls

below 20C

28
Q

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

A
  • flow becomes pressure dependent

- luxury flow (flow&raquo_space; metabolic rate)

29
Q

Cerebral Blood Flow

– pH-stat uncouples what?

A

flow and metabolism

30
Q

Cerebral Blood Flow

– Alpha-stat maintains?

A

maintains autoregulation

31
Q

Cerebral Blood Flow

– pH-stat uncouples flow and metabolism which means greater bld flow is __ dependent

A

greater blood flow–pressure dependent

32
Q

Cerebral Blood Flow

– pH-stat Luxury Flow predisposes what? (3)

A
  • predispose to risk of embolic injury
  • high intracranial pressure
  • edema
33
Q

Cerebral Blood Flow

- alpha stat lower blood flow–based on?

A

lower blood flow–based on metabolism

34
Q

Cerebral Blood Flow

- alpha stat predispose to ?

A

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

35
Q

pH or alpha stat?

PROFOUND ARREST w/ADULTS

A

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

36
Q

pH or alpha stat?

INFANTS

A

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

37
Q

pH or alpha stat?

REGULAR BYPASS ADULTS: With little or no hypothermia

A

With little or no hypothermia might not make any difference.

38
Q

pH or alpha stat?

REGULAR BYPASS ADULTS: With mild to moderate hypothermia

A

With mild to moderate hypothermia alpha-stat might be better

39
Q

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

A

Alpha stat

40
Q 
keep corrected PCO2 equal to the patient’s
core temperature (i.e. PCO2 will decrease) and corrected pH will increase
A

Alpha stat

41
Q

Alpha stat - look at which pH and PCO2 values?

A

uncorrected pH and PCO2 values at normal levels

42
Q

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

A

pH stat

43
Q

pH stat - looks at which pH and PCO2 values?

A

keep corrected pH and pCO2 values

uncorrected pH will decrease and the uncorrected PCO2 will increase

Perf Tech II (exam 1) (9 decks)

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