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PHARM EXAM 1 > GAS LECTURE II > Flashcards

GAS LECTURE II Flashcards

1
Q

What factors affect absorption (uptake) of gasses?

A 
Ventilation
Blood uptake (to increase: increase MV, second gas, overpressurize)
BGSC
Cardiac output
Alveolar partial pressure difference
Temperature
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2
Q

What factors affect distribution?

A

MAC/potency/OGSC
Temperature (hyperthermia increases MAC, hypothermia decreases MAC)
CO- distribution to VRG
Hypo/hypernatremia

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3
Q

What factors effect Elimination?

A

Metabolism (sevo metabolized 5-8%)
Temperature (hypothermia- slows recovery)
Longer case- slower emergence
High solubility- slower emergence
Higher minute ventilation- faster emergence

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4
Q

Factors affecting Inspiratory Concentration

A

Fresh gas flow- (increase flow to increase Fi)
Breathing system volume (increase TV)
Machine absorption (increase flow >5L/min, increase concentration)

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5
Q

Factors affecting Avelolar Concentration

A

Uptake (BGSC)
Alveolar Blood Flow
Partial pressure difference from alveoli to blood

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6
Q

Factors affecting Arterial Concentration

A

Ventilation/perfusion mismatch

  • venous admixture
  • uneven distribution
  • alveolar dead space
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7
Q

How to increase FA/Fi?

A 
Over pressurize
Second gass effect
Increase flow of carrier gas
Increase minute ventilation
Decrease CO
Use gas with lower BGPC
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8
Q

How is cardiac output distributed?

A

75% VRG
19% muscle
6% fat

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9
Q

What are the effects of a Right Bronchial Intubation (V/Q mismatch?)

A

Increase in alveolar partial pressure (high solubility agents)
Decrease in arterial partial pressure (low solubility agents)

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10
Q

Where does amnesia happen?

A

Brainstem

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11
Q

Where does analgesia happen?

A

Spinothalamic tract

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12
Q

Where does areflexia happen?

A

Spinal Cord

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13
Q

What are the most likely targets of gasses?

A 
NMDA
Tandem pore K channels
GABA A
VG Na Channels
Glycine Receptors
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14
Q

What is the Meyerton Overton theory?

A

Lipophilicity equates to potency

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15
Q

Explain the critical volume hypothesis (Meyerton-Overton Theory)

A

Once a critical amount of gas is on board, gas will cross lipid bilayer and exert level of action and some level of distortion of ion channels.

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16
Q

Rank CNS effects in order of dose requirements.

A

Least - Most

  1. amnesia
  2. sedation
  3. LOC
  4. Immobility
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17
Q

What effect do gasses have on cerebral metabolic rate of oxygen consumption?

A

CMRO2 is decreased (except NO)

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18
Q

What effect do gasses have on cerebral blood flow?

A

Dose-dependent increase on cerebral blood flow.

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19
Q

What is uncoupling?

A

Increase of cerebral BF but decrease of CMRO2.

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20
Q

What drug has greatest effect on uncoupling effect?

A

Sevo

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21
Q

What effect does Nitrous oxide have on CNS? How is this affect mediated?

A

NO increases CMRO2 and CBF. Attenuate increased CBF with mild hyperventilation.

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22
Q

What effect do gasses have on cerebral vascular responsiveness to CO2?

A

Preserve body’s effect: vasoconstrict in hypocapnia and vasodilate in hypercarbia.

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23
Q

What can be done to mediate the effect of gasses on in CBF?

A

Mild hyperventilation to keep CO2 30-35– low CO2 leads to cerebral vasoconstriction.

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24
Q

What effect do gasses have on EEG activity?

A

Dose-related suppression

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25
Q

What effect do gasses have on burst suppression? What dose does it take to cause burst suppression

A

Burst suppression- pt is in coma

1.5 MAC des 2.0 MAC sevo

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26
Q

What effect do gasses have on evoked potentials?

A

They increase latency and decrease amplitude.
During spine surgery may need to use TIVA because can’t tell if there is a spinal cord issue or if effect is being caused by gas.

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27
Q

What effect does anesthesia have on developmental neurotoxicity?

A

Animal studies show anesthesia is toxic to brain development but human studies (PANDA, GAS trial, population-based cohort study) found no evidence of this.

Theory in animal study: activation of intrinsic and extrinsic apoptic cell death.

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28
Q

What recommendations are in place for gas use in children?

A

Keep surgery short

Use short acting drugs and multimodal approaches.

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29
Q

What are the effects of gas on postoperative cognitive dysfunction?

A

No long term effects

Higher concern in elderly

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30
Q

Describe the effects of emergence delirium in children.

A

Self limiting, no long term effects.
Can cause injury or delay d/c because of sedatives
Preventative measures: quiet stress free environment, reduce pain, reduce pre-op anxiety, reunite w/ parents

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31
Q

What medications are used to treat emergence delirium in children?

A

Precedex is the main one

also midazolam, fentanyl, ketamine, clonidine, dexamethasone, NSAIDS

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32
Q

What effect do gasses have on CO/CI?

A

Volatile agents reduce CO/CI in dose dependent fashion because they reduce free Ca2+ in cell.

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33
Q

How do gasses affect HR?

A

SA node antagonism
Modulate baroreceptor reflex activity
Activate SNS

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34
Q

What gasses lower CO?

A

Des, sevo, iso.

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35
Q

What does xenon affect?

A

lower heart rate. No effect on other hemodynamics (keeps everything else the same).

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36
Q

What gasses lower SVR?

A

Iso (most), sevo, des

37
Q

What is nitrous affect on SVR?

A

Increase or stay the same, does not decrease

38
Q

What gasses lower MAP?

A

Iso (most), sevo, des (all lower MAP by lowering SVR).

39
Q

What is NO effect on MAP?

A

Increase or stay the same, does not decrease

40
Q

What gasses increase HR?

A

Iso, Des, NO

41
Q

What is the reverse robin hood syndrome?

A

In the presence of hypotension, reduction of perfusion to ischemic myocardium and increase of perfusion to non-ischemic tissue.

42
Q

What drug produces the most profound robin hood syndrome?

A

Iso

43
Q

What is preconditioning?

A

A phenomenon in which the heart is exposed to a cascade of intracellular events that protect it from ischemic and reperfusion insult. Happens with iso, sevo, des- gas exposes heart to mild level of ischemia- pre-conditions heart so that if it were to have real ischemia it would be ready.

44
Q

What gas does not usually increase HR?

A

Sevo

45
Q

What is sensitization?

A

Volatile agents reduce the quantity of catecholamines necessary to evoke arrythmias. So you get more arrythmias

46
Q

What is a safe epi dose with volatile anesthesia?

A

10ml of 1:100,000 epi in a 10 min period or up to 30ml/hr

47
Q

What drug increases PVR?

A

NO. Effect worsens in presence of pulmonary HTN.

48
Q

Do volatile agents increase or decrease PA pressure?

A

Decrease

49
Q

What effects do volatile agents have on hypoxic pulmonary vasoconstriction?

A

They decrease HPV (iso decreases it the most). Naturally, body shunts blood away from vasoconstricted lungs. Gas stops this - vasoconstricted lungs get perfused.

50
Q

What are the respiratory effects of gasses?

A

Dose dependent TV decrease
Increase in RR (compensation for decreased TV) initially, then decrease RR
Decreased responsiveness to CO2 (decreases apneic threshold, exacerbated if opioid given)
Decreased response to hypoxemia
Relax airway smooth muscle & Bronchodilate

51
Q

What gas is an airway irritant?

A

Des. Don’t inhalationally induce with des.

52
Q

How do volatile agents impact renal system?

A

Autoregulation of renal circulation remains intact

Decrease in renal SVR leads to decline in GFR (leads to decrease in UOP).

53
Q

What gas alters renal function least?

A

Des

54
Q

How does sevo affect renal function?

A

Liver metabolizes 5-8% of Sevo - creates compound A- free fluoride ions. Can be nephrotoxic.

55
Q

What are the recommendations for Sevo (in regards to renal toxicity)?

A

Should not exceed 2 MAC hours at flows <2L/min

Fresh gas flow <1L/min not recommended

56
Q

What effects do volatile agents have on liver function?

A 
All volatile agents have potential to impair liver function
Halothane hepatitis (antibody mediated response)
Rare for current volatile gasses to impair liver function (not metabolized by liver)
No significant impact on hepatic flow
57
Q

What gas undergoes hepatic metabolism?

A

Sevo (5-8%)

58
Q

What effects do gasses have on neuromuscular system?

A

Dose dependent relaxation of skeletal muscle
Additive effect on non depolarizing NMBDs
Can reduce dose of NMBDs by 25-50% with gas
Delay recovery from NMBDs
NO has no effect of skeletal muscle relaxation/NDMRs

59
Q

Which gasses can cause malignant hyperthermia?

A

All except NO

60
Q

What are the signs of MH?

A 
Increase in EtCO2 (most telling sign)
muscle rigidity (hidden in paralysis)
Increase in body temp (late sign)
Urine color darkens
Tachycardia
Tachypnea

presentation can be delayed or slowed

61
Q

What drugs are used to treat MH?

A

Dantrolene (1mg/kg)- supplied in 70ml vials with 20mg dantrolene, 3000 mg mannitol, sodium hydroxide. Give until symptoms subside, up to 10mg/kg

Ryanodex- IV form of dantrolene. Requires fewer vials and less reconstitution. Need to add mannitol. Shorter half life. More expensive.

62
Q

How does obesity affect anesthesia?

A

Slower emergence

63
Q

How does pregnancy affect anesthesia?

A

Decrease MAC
Should delay elective surgery until after delivery
Delay surgery until second trimester if possible
NO- teratogenic effects

64
Q

Properties of an ideal anesthetic

A 
non irritating to respiratory tract
rapid induction/emergence
chemically stable
non flammable
produce amnesia, analgesia, areflexia
Potent
Not metabolized/excreted via respiratory tract
Free of toxicity/allergic reactions
Minimal systemic changes
Uses standardized vaporizer
Affordable
65
Q

What 4 properties affect how agents work?

A

Vapor pressure
Solubility
Partial pressure
Boiling point

66
Q

What do vaporizers do?

A

Facilitate movement of anesthetic from machine to patient through fresh gas flow, pressure, temperature. Calibrated for specific agents.

67
Q

what gas is known to produce tachycardia on induction?

A

Des (also iso to a lesser extent).

Can be prevented by increasing concentration slowly.

68
Q

What gas does not cause bronchodilation?

A

NO

69
Q

What gas has no effect on respiratory rate, response to hypercarbia, response to hypoxemia?

A

NO

70
Q

What is the only gas contraindicated in pregnancy?

A

NO

71
Q

What gas usually causes emergence delirium in children?

A

Sevo and des (they wear off quickly).

72
Q

How would a shunt affect iso?

A

Increase in alveolar partial pressure

73
Q

How would a shunt affect des or sevo?

A

Decrease in arterial partial pressure

74
Q

Which drug does not cause cardiac output decrease?

A

NO

75
Q

How can you remediate the decreased CO and SVR caused by volatile agents?

A

Add NO- additive effect and does not decrease CO. WIll allow you to use less of the other drug.

76
Q

What should you do when someone is in stage 2 anesthesia?

A

NOTHING

77
Q

How does decrease CO and SVR change throughout case?

A

With increase in MAC hours, CO and SVR will increase

78
Q

Which gas has biggest decrease in hypoxic pulmonary vasoconstriction?

A

Iso

79
Q

Which gas causes most bronchodilation?

A

Sevo

80
Q

Patient has bronchospasm during case- what do you do?

A

Increase gas

81
Q

How do absorbents affect nephrotoxicity?

A

With older absorbents (Ca, Lithium) Compound A production was an issue. With new ones (KOH, NaOH) it’s not

82
Q

What organ is affected by sevo metabolism?

A

Kidney (free fluoride ions) NOT LIVER

83
Q

Which gas has an isolated cl- ion?

A

Iso

84
Q

which gas is not an ether?

A

halothane

85
Q

which gas causes cardiac sensitization?

A

halothane

86
Q

What needs to happen for reverse robin hood effect to occur?

A

HYPOTENSION

87
Q

what drug should you use for an inhalational induction?

A

Sevo

88
Q

what drug should you avoid in athsma?

A

Des

89
Q

What precautions should you take when using sevo

A

do not exceed 2 MAC hours at flows <2L/min

use modern absorbent (KOH or NaOH)

PHARM EXAM 1 (1 decks)

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