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

Exam 1 - Acid Base Management Flashcards

(48 cards)

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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

Study These Flashcards
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

Study These Flashcards
A
  • Report gas values at 37C
22
Q

Corrected gases

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

pH change per degree

Study These Flashcards
A

0.0147 drop in pH per increase in degree C

24
Q

ALWAYS use temperature corrected values for…

25
3 H+ equations
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
3 big buffer players
- 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
Alpha and pH stat only affect...
- pCO2 and pH | - Arterial pO2 MUST be temperature corrected
28
Normal pCO2
40 mmHg
29
Normal pH
7.4 at 37C
30
Why does pH change when CO2 is added
Increase in H+ ions CO2 + H2O H2CO3 HCO3- + H+
31
Alpha stat
- 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
pH stat
- 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
pH vs body temperature
- vary inversely | - in body... temperature (and pH) will vary from organ to organ
34
Advantages of constant CO2 content (alpha stat)
- 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
Consequences of pH stat during Hypothermia
- 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
Consequences of alpha stat during hypothermia
- 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
pH stat and tissue oxygenation
- shifts oxy-hemo curve right which offsets left shift due to hypothermia
38
CO2 as a vasodilator
- pH stat: increases / maldistributes blood flow | - alpha stat: improve peripheral perfusion because we maintain auto regulation
39
Cerebral blood flow in pH stat
- 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
Luxury flow
Flow to brain is higher than metabolic need of brain
41
Cerebral flow in alpha stat
- lower blood flow - based on metabolic need - risk of adverse flow distribution, ischemic injury ~ more so in infants/peds
42
Best strategies
- alpha: regular adult bypass if mild to moderate - pH stat: infants - Combo - pH to cool / alpha to warm: profound arrest w/ adults
43
Managing pH stat
- keep pH constant - keep temp corrected pCO2 at 40 - keep temp corrected pH at 7.4
44
Normal bicarb
22-26
45
Normal SvO2
70
46
Normal pO2
150-250 on pump
47
Managing alpha stat
- 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
If brain oxymetry says need more flow....
- Give more CO2

562 - Perfusion Technology II (9 decks)

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