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Peds 2 > Pharmacology of Nitrous Oxide > Flashcards

Pharmacology of Nitrous Oxide Flashcards

1
Q

How is Nitrous distributed?

A

blue cylinders that have 30% liquid, 70% gas when full

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2
Q

what are the chemical properties of Nitrous?

A
  • stable at room temp
  • cools with vaporization
  • hardly metabolized
  • non-flammable
  • will support combustion if heated high enough
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3
Q

who pure must nitrous be for medical use?

A

99%

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4
Q

what are the physical properties of Nitrous?

A
  • nonirritating
  • slightly-sweet smelling (odor overwhelmed by rubber)
  • colorless
  • inorganic (UNLIKE ALL OTHER ANESTHETIC GASES)
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5
Q

how is the dose of nitrous quantified?

A

by the concentration (percentage) delivered

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6
Q

how is the potency of nitrous measured?

A

minimum alveolar concentration (MAC)

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7
Q

when do the effects of nitrous wear off?

A

usually minutes following end of delivery

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8
Q

the alveolar conc. at which 50% of the population will not respond (with movement) to a standard surgical incision

A

minimum alveolar concentration (MAC)

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9
Q

what is the MAC of nitrous?

A

104%

*most major anesthetic gases have a MAC of 1-6%

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10
Q

is nitrous the most/least potent of all anesthetic gases used?

A

least

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11
Q

is GA possible with nitrous?

A

yes but rare

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12
Q

a measure of affinity of blood for the gas - the ratio at equilibrium btw blood and gas concentrations

A

blood-gas solubility

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13
Q

what is the solubility coefficient for N2O?

A

0.47

  • poorly soluble in blood
  • high gas tension maintained in alveoli
  • rapid entry, rapid removal from blood via lungs
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14
Q

poos solubility in blood leads to what?

A

high conc in highly perfused tissues

  • mostly brain
  • fat, skeletal mm NOT sig reservoir
  • reason for rapid recovery
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15
Q

what is the conc effect of nitrous?

A
  • high levels are taken up rapidly into blood
  • this sucks more gas into lungs
  • effect is as if higher conc was given
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16
Q

how long does it take for blood-brain saturation

A

3-5 minutes

17
Q

what is diffusion hypoxia?

A
  • when nitrous oxide enters lungs form blood rapidly
  • this pushes other gases out, including O2
  • to avoid give pts 100% O2 for 3-5 minutes after use
18
Q

dec perception of pain

A

analgesic

19
Q

what are the effects on the cardiovascular system?

A
  • minimal effects at useful conc
  • no change in HR, cardiac output
  • often see drop in BP from reduced anxiety
  • may see slight peripheral vasodilation, causes flushing
20
Q

what are the effects on the central nervous system?

A
  • affects all forms of sensation
  • tingling, hearing changes
  • mild CNS depression, especially of thinking centers (memory concentration, ability to reason)
21
Q

what are the effects on the respiratory system?

A
  • nonirritating (OK with pulmonary disease)

- may see change in rate, depth of respiration from reduced anxiety

22
Q

what are the effects on the GI system?

A
  • no direct effects

- may distend gas-filled intestine in bowel obstruction pt

23
Q

what are the effects for the renal system?

A

none

24
Q

what are the effects for the hepatic system?

A

none

25
Q

what are the effects for the hematologic system?

A

chronic exposure may depress bone marrow activity

26
Q

what are the effects for the skeletal m?

A

relaxation from reduced anxiety

27
Q

what are the effects for pregnancy?

A
  • NOT a contraindication
  • used during labor and delivery
  • DOES cross the placenta but without apparent effect at usual concentrations
  • is prudent to avoid if possible (like all drugs) esp during first trimester
28
Q

when should N2O be avoided?

A
  • if pt refuses
  • if pt has psychosis, uncontrolled depression

*use with caution in pts with severe COPD and emphysema

29
Q

what does chronic exposure lead to?

A
  • bone marrow depression secondary to abusive exposure
  • sensory depression from peripheral neuropathy (tingling fingers)
  • possible inc in spontaneous abortion rate

Peds 2 (9 decks)

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