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562 - Perfusion Technology II > Exam 1 - Acid Base Management > Flashcards

Exam 1 - Acid Base Management Flashcards

1
Q

Acid

A

Ability to donate H+

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2
Q

Base

A

Ability to accept H+

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3
Q

pH

A

pH = -log[H+]

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4
Q

Dissociation curve shifts left if…

A
  • Temp decreases
  • Energy decreases
  • Dissociation decreases
    - concentration of ions decrease
  • pH increases
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5
Q

pH of neutrality

A

pH produced when water dissociates

- pH = 7.0 at 27C

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6
Q

Henry’s Law

A

Dissolved (total) gas = Solubility x Partial Pressure

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7
Q

Solubility of CO2 @ 37C

A

0.06 mls CO2 / 100 mls blood / mmHg

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8
Q

Solubility of O2 @ 37C

A

0.003 mls O2 / 100 mls blood / mmHg

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9
Q

Partial pressure of air phase vs. liquid phase

A

Equal at equilibrium

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10
Q

Forms of CO2 from tissue to lungs

A
  • Dissolved
  • Bound to hemoglobin (limited ceiling)
  • As HCO3
    ~ conversion happens in RBC VI’s carbonic anhydrase
    ~ unlimited ceiling
  • All add up to total CO2 content
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11
Q

Haldene effect

A

Venous blood hemoglobin has greater affinity to CO2 due to lower O2 content

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12
Q

Solubility vs Temperature

A

If temp goes up….solubility of gas goes down

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13
Q

How to change pH of blood in CLOSED system

A
  • Change total CO2 content (temp constant)
  • Change temp (total CO2 constant)
  • Change temp AND total CO2 content
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14
Q

CO2 vs pH

A

If CO2 goes up….pH goes down

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15
Q

Increasing total CO2 content by adding CO2

A
  • pCO2 increases
  • pH decreases
  • visa versa
  • Assuming no change in temp/ solubility / disassociation equilibrium
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16
Q

Increasing temperature affect

A
  • Drive disassociation equilibrium to the right
    - the reason for the change in pH
  • [H+] increases
  • pH decreases
  • visa versa
  • Assuming no change in total CO2
  • pCO2 changes because solubility changes…but NO change in pH
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17
Q

If temperature increases in closed system…

A
  • Gas solubility DECREASES
  • Gas partial pressure INCREASES
  • Gas pressure is GREATER than starting pressure
  • Equilibrium shifts RIGHT
  • pH DECREASES
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18
Q

If Temperature decreases in a closed system

A
  • Gas solubility INCREASES
  • Gas partial pressure DECREASES
  • Gas pressure is LESS than starting pressure
  • Equilibrium shifts LEFT
  • pH INCREASES
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19
Q

What is needed to draw a sample

A
  • Waste syringe (for venous draw)
  • Sample syringe
  • Cup of ice (if going to lab)
  • Draw from patient / ECC / remove air from sample
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20
Q

Blood gas determination in lab

A
  • Analyzer warms sample to 37C
  • determines pO2, pCO2, and pH at 37C
  • At 37C…solubility decreases…pO2/pCO2 will be artificially high
  • Pushes HOH equation right so pH will be artificially low at 37C
21
Q

Uncorrected gases

A
  • Report gas values at 37C
22
Q

Corrected gases

A
  • Gas values measured at 37C BUT corrected back to actual body temperature
23
Q

pH change per degree

A

0.0147 drop in pH per increase in degree C

24
Q

ALWAYS use temperature corrected values for…

A

pO2

25
Q

3 H+ equations

A

HOH OH- + H+
CO2 + H2O H2CO3 HCO3- + H+
Protein+ Protein + H+

  • A change in one of these will have an effect on the other two
  • Increasing H+ will shift others left
26
Q

3 big buffer players

A
  • Bicarb
  • Protein
  • Phosphate
  • 16:1 OH:H buffer ratio despite changes in temperature
  • Main blood buffering system is imidazole side chain of histidine
    - accounts for most of pH change due to changes in temp
27
Q

Alpha and pH stat only affect…

A
  • pCO2 and pH

- Arterial pO2 MUST be temperature corrected

28
Q

Normal pCO2

A

40 mmHg

29
Q

Normal pH

A

7.4 at 37C

30
Q

Why does pH change when CO2 is added

A

Increase in H+ ions

CO2 + H2O H2CO3 HCO3- + H+

31
Q

Alpha stat

A
  • Total CO2 content held constant with change in temp
  • Values will drift naturally as temp drops
    ~due to solubility changes and Imidazole disassociation shift
  • What happens to our bodies on daily basis
    ~between pulmonary caps and systemic caps
  • Alpha ratio held constant
32
Q

pH stat

A
  • Hold pCO2 and pH at constant level with change in temp
  • What happens in reptiles / cold blooded animals
  • Total CO2 content MUST increase to maintain levels
    ~add CO2 as temp decreases and remove CO2 as temp increase
    ~ must blow off CO2 when rewarming
  • Alpha ratio changes as CO2 content increases
33
Q

pH vs body temperature

A
  • vary inversely

- in body… temperature (and pH) will vary from organ to organ

34
Q

Advantages of constant CO2 content (alpha stat)

A
  • constant pH across cell membranes
  • constant ratio of - to + charge on proteins
  • allows enzymes to work at optimal level regardless of temp
  • Keeps metabolic activity up even at low temps
35
Q

Consequences of pH stat during Hypothermia

A
  • Blood more acidic
  • ion gradient across cell membrane changes
  • acidity alters metabolic activity (not always bad in surgery)
  • cells do not maintain neutrality (bad)
  • added CO2 influences blood flow regulation…big in brain
    ~ biggest effect
36
Q

Consequences of alpha stat during hypothermia

A
  • constant charge on histamine side chain
  • ion gradient across cell is constant
  • enzyme functions maintained (metabolic activity higher in surgery)
  • cells maintain neutrality
  • auto-regulation of blood flow maintained…based on metabolic need
37
Q

pH stat and tissue oxygenation

A
  • shifts oxy-hemo curve right which offsets left shift due to hypothermia
38
Q

CO2 as a vasodilator

A
  • pH stat: increases / maldistributes blood flow

- alpha stat: improve peripheral perfusion because we maintain auto regulation

39
Q

Cerebral blood flow in pH stat

A
  • normally tightly auto regulated
  • below 20C….lose autoregulation (for both stats)
  • pressure dependent…greater blood flow
  • improved cooling (due to more flow)
  • Luxury flow
  • Risk of embolic injury, high brain pressure, edema
    ~ more so in adults
40
Q

Luxury flow

A

Flow to brain is higher than metabolic need of brain

41
Q

Cerebral flow in alpha stat

A
  • lower blood flow - based on metabolic need
  • risk of adverse flow distribution, ischemic injury
    ~ more so in infants/peds
42
Q

Best strategies

A
  • alpha: regular adult bypass if mild to moderate
  • pH stat: infants
  • Combo - pH to cool / alpha to warm: profound arrest w/ adults
43
Q

Managing pH stat

A
  • keep pH constant
  • keep temp corrected pCO2 at 40
  • keep temp corrected pH at 7.4
44
Q

Normal bicarb

A

22-26

45
Q

Normal SvO2

A

70

46
Q

Normal pO2

A

150-250 on pump

47
Q

Managing alpha stat

A
  • keep total CO2 constant…allow pH to change
  • target values change with temp
  • use NOT corrected values for pCO2 and pH and keep normal
  • can compare patient core temp to corrected pCO2 and keep same
48
Q

If brain oxymetry says need more flow….

A
  • Give more CO2

562 - Perfusion Technology II (9 decks)

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