CO2 Absorption Flashcards

1
Q

how does CO2 cause acidosis?

A

CO2 combines with H2O to form H2CO3 (carbonic acid)

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2
Q

how does absorbent work?

A

-soda lime or calcium lime (salts) neutralize carbonic acid to water and energy (heat)

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3
Q

what is the most common absorbent?

A

soda lime

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4
Q

what are the ingredients of different absorbents?

A
  • soda lime: NaOH (sodium hydroxide)
  • calcium lime: Ca(OH)2 (calcium hydroxide)
  • KOH (potassium hydroxide) (least used)
  • a little water added to all
  • silica added to decrease dust and resistance
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5
Q

how does pH indicator of absorbent work?

A

-turns white absorbent to purple (or pink) as acid levels
builds indicating absorbent exhaustion
-replace with 50-70% (usually 50%) color change
-absorbent can revert back to original color with rest, but
absorbency is NOT restored

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6
Q

what is mesh?

A

the number of holes per linear inch of a screen

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7
Q

how many mesh are most CO2 absorbents?

A

4-8 (more so 8) (bigger the number, the smaller)

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8
Q

what is dessicated absorbent?

A

very dry absorbent

*leads to higher volatile gas degradation

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9
Q

What are volatile agents degraded to with dessicated absorbent?

A
  • desflurane to carbon monoxide (CO)
  • sevoflurane to compound A
  • degradation is worst with KOH
  • Amsorb is a newer CO2 absorbent resulting in less degradation
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10
Q

what is Compound A?

A

by-product of sevoflurane degradation by absorbent

*nephrotoxic at 25-50 ppm (easily created with low flows)

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11
Q

what increases the risk of Compound A formation?

A
  • high concentrations of Sevo
  • long anesthesia time (> 2 MAC hours)
  • Low flow techniques (< 2 L/min)
  • *with typical CO2 absorbents, must run Sevo with high flows (> 2 L/min)
  • *longer cases may want to run Sevo at O.5 MAC over a few hours to stay below 2 MAC hours
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12
Q

What is the benefit of Amsorb absorbent use?

A

-allows for lower flows of Sevo without degradation into Compound A

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13
Q

what is channeling?

A

absorbent exhaustion in areas where gas enters the absorber and along the canister walls
-baffles in the absorber direct gas flow through the center to minimize channeling

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14
Q

how can you prevent dessication and exhaustion of absorbent?

A
  • avoid absorbents with KOH if possible
  • create/enforce policies to prevent dessication
  • turn off all gas flow when machine is not in use
  • change absorbent on scheduled basis
    (i. e. once a week on the same day)
  • change compact canisters frequently
  • use low flows as much as possible (high flows dry out)
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15
Q

what can you do if you notice your patient’s inspired CO2 increasing in the middle of a case and you have 70% of absorbent is purple?

A
  • most likely exhausted absorbent
  • FGF 0.3- 0.5 L/min almost total rebreathing
  • increase flows of 5-8 L/min allowing little absorbent work and CO2 is flushed to scavenger via high flow
  • change absorbent at end of case
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