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PMI > Inhalational Anesthetics > Flashcards

Inhalational Anesthetics Flashcards

1
Q

Nitrous oxide properties (10)

A
  1. ) clinically considered only inhalational agent w/ analgesic properties
  2. ) associated with PONV
  3. ) increases pulmonary vascular resistance
  4. ) dilates cerebral vasculature
  5. ) raises the seizure threshold
  6. ) it supports combustion as much as O2
  7. ) it can cause postoperative diffusion hypoxia
  8. ) expands closed air containing cavities
  9. ) increases the cerebral metabolic rate of O2
  10. ) prolonged exposure can lead to harmful effects (bone marrow depression, can inhibit enzymes involved in DNA synthesis, and neurologic deficiencies)
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2
Q

Contraindications for nitrous oxide (8)

A
  1. ) laryngeal/ pharyngeal/facial surgery with a laser or bovie
  2. ) ophthalmic sx
  3. ) pts w/ severe COPD
  4. ) cardiopulmonary bypass sx
  5. ) prolonged intestinal procedures and bowel obstruction and laparoscopic sx
  6. ) inner ear surgery
  7. ) 1st trimester of pregnancy
  8. ) neurosurgery situations (intracranial pressure, craniotomy, after dural closure)
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3
Q

which volatile agent causes coronary steal phenomenon?

A

isoflurane

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4
Q

Describe the coronary steal phenomenon

A

when isoflurane causes coronary vasodilation the stenotic coronary arteries cannot vasodilate as well as the normal coronary arteries

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5
Q

Advantages of isoflurane (2)

A
  1. minimal cardiac depression

2. causes coronary vasodilation

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6
Q

refers to highest blood CO2 level

A

apneic threshold

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7
Q

3 anesthetics that can increase apneic threshold

A
  1. propofol
  2. fentanyl
  3. volatile agent
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8
Q

pt can hold their breath for longer time before they need to start breathing; have LESS of a drive to breathe

A

high apneic threshold

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9
Q

pt cant hold their breath for as long (cant let CO2 get very high) before they need to start breathing; more of a drive to breathe

A

low apneic threshold

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10
Q

how do anesthetics affect apneic threshold?

A

RAISE apneic threshold; suppress the pt’s drive to breathe which means it will take a much higher CO2 than normal in order to stimulate breathing

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11
Q

how does pain affect apenic threshold?

A

lowers apneic threshold by stimulating respirations

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12
Q

Assume pt is on ventilator. how do you get pt to spontaneously ventilate?

A
  1. ) reverse paralysis (if necessary)
  2. ) allow the pt’s Co2 to increase (either slow down their RR, or shut the vent off completely)
  3. ) pt will begin to breathe when apneic threshold has reached (when CO2 is high enough)
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13
Q

refers to lowest oxygen level at which pt can no longer remain apneic

A

hypoxic drive

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14
Q

hypoxic drive in a normal pt

A

PaO2 = 60 mm Hg

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15
Q

what has a greater effect to stimulate breathing in healthy pts?

A

hypercarbia

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16
Q

what has a greater effect on stimulating breathing in pts with LUNG disease?

A

hypoxia

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17
Q

respond to changes in H+ ion concentration of CSF determined by PaCO2

A

central chemoreceptors

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18
Q

in carotid body; affect ventilation by responding to changes in PaO2

A

peripheral chemoreceptors

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19
Q

2 goals of MAC

A
  1. ) keep pt asleep/ prevent consciousness/awareness

2. ) prevent movement

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20
Q

If a pt is exhaling 6% MAC of desflurane.. what does that mean?

A

they are 50% likely to move when they are cut

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21
Q

Is it easier to prevent awareness or prevent movement?

A

prevent awareness

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22
Q

Why would you want to paralyze pt?

A

you want to keep pt from moving WITHOUT deeply anesthetizing pt

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23
Q

MAC refers to ____.

A

minimum alveolar concentration of an EXHALED gas that will prevent movement in 50% of patients during surgical incision

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24
Q

end tidal concentration of volatile agent will be (lower or higher) than the concentration on the vaporizer dial

A

lower

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25
Q

MAC reflects ____

A

potency

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26
Q

when are patients less likely to move?

A

when breathing a higher percentage (MAC value) of agent

27
Q

MAC value for awake (no stimulation)

A

0.4 MAC

28
Q

MAC value for reliable awareness prevention (if narcotics are used)

A

0.8 MAC

29
Q

MAC value for reliable awareness prevention (even w/o narcotics)

A

1.0 MAC

30
Q

MAC value for 50% chance of movement (w/o paralytics)

A

1.0 MAC

31
Q

MAC value for 5% chance of movement (w.o paralytics)

A

1.3 MAC

32
Q

Is it possible for a patient to move without awareness?

A

Yes

33
Q

Is it possible for a patient to be aware without moving?

A

yes; only if a paralytics given

34
Q

How do we know if patients are aware or not when they’re paralyzed?

A

vital signs; if pt is aware: HR & BP >200

35
Q

2 reasons to give volatile agents?

A
  1. ) prevent movement

2. ) prevent awareness

36
Q

to reliably prevent movement in a NON-PARALYZED patient, the pt should exhale how much volatile agent?

A

greater than or equal to 1 MAC; and have narcotics dosed prior to incision

37
Q

To reliably prevent awareness in a patient w/ no narcotic use should be exhaling ?

A

greater than or equal to 1 MAC

38
Q

to reliably prevent awareness in a patient w/ narcotic use the patient should be exhaling?

A

greater than or equal to 0.8 MAC

39
Q

Factors that DECREASE MAC (6)

A
  1. ) IV anesthetics
  2. ) old age
  3. ) ACUTE alcohol intoxication
  4. ) pregnancy
  5. ) temperature related factors (hypothermia, mild hyperthermia)
  6. ) blood related factors (hypoxia, hypercarbia, hypotension, anemia)
40
Q

Factors that INCREASE MAC (4)

A
  1. ) Young
  2. ) Hot (extreme hyperthermia >42 deg. celsius)
  3. ) Salty (hypernatremia)
  4. ) Alcoholic (chronic alcohol)
41
Q

pt is hypertensive and tachycardic. they are exhaling 0.7% sevoflurane. what are acceptable tx?

A
  1. ) propofol (pt is breathing 0.35)
  2. ) narcotics
  3. ) more volatile agent
  4. ) NO beta blockers or antihypertensives
42
Q

what does desflurane’s 0.42 B:G coefficient mean?

A

once equilibrium is reached, the blood is only 42% saturated compared to the lung. Des is not very soluble in blood

43
Q

True/False: if an agent is not very soluble in the blood, the blood will have less agent and a lower coefficient

A

TRUE

44
Q

Isoflurane B:G coefficient is 1.4 what does that mean?

A

the blood is 40% more saturated than lungs and it’s a lot more soluble in the blood than des

45
Q

If there are 30 volatile agent molecules in the alveoli and 25 in the blood what is the B:G coefficient?

A

25/30= 0.83; blood is 83% saturated compared to lungs

46
Q

Neurologic effects of Volatile Agents (4)

A
  1. dilates the cerebral vasculature, increases cerebral blood flow, increases intracranial pressure
  2. can cause emergence delirium in kids
  3. decrease the possibility of seizures
  4. decrease the cerebral metabolic rate of oxygen
47
Q

Cardiac effects of volatile agents (3)

A
  1. decrease cardiac contractility
  2. cause systemic vasodilation
  3. cause coronary vasodilation
48
Q

which volatile agent causes the greatest degree of coronary vasodilation ?

A

isoflurane

49
Q

Respiratory effects of volatile agents (4)

A
  1. ) rapid shallow breathing causing CO2 to increase
  2. ) increase a patient’s apneic threshold
  3. ) decrease a patient’s hypoxic drive
  4. ) cause bronchodilation
50
Q

higher levels of CO2 is most likely going to drop a patient’s ____

A

minute ventilation

51
Q

Other effects of Volatile Agents (6)

A
  1. decreases renal blood flow
  2. decreases hepatic blood flow
  3. prolongs muscle relaxants
  4. associated with PONV
  5. All volatile agents trigger malignant hyperthermia
  6. Inhibit “non shivering thermogenesis” in pediatric pts
52
Q

how does nitrous oxide expand air bubbles?

A

when blood comes into contact with air pocket, the NITROUS OXIDE will diffuse into the air pocket faster than nitrogen can diffuse into the blood. this causes pocket expansion

53
Q

nitrous oxide ___ pt’s FiO2 and _____ the risk of pneumothorax

A

decreases; increases

54
Q

Which gas causes coronary steal phenomenon?

A

isoflurane

55
Q

describe coronary steal phenomenon

A

when isoflurane causes coronary vasodilation, the stenotic coronary arteries cannot vasodilate as well as the normal coronary arteries. normal arteries receive more blood flow but stenotic arteries receive decreased blood flow

56
Q

Which agent is ideal for mask induction ?

A

sevoflurane

57
Q

disadvantages of Sevo?

A
  1. ) releases nephrotoxic free fluoride ions when metabolized
  2. ) can release “compound A” when broken down by a soda lime CO2 absorber
58
Q

effects of compound A are more significant with ____, _____, and ____.

A

prolonged exposure to sevoflurane, high concentrations of sevoflurane, low fresh gas flow used

59
Q

What is the FDA recommendation for using sevoflurane with fresh gas flow rates?

A

at least 1L/min for exposure up to 1 hr and at least 2 L/min for exposures greater than 1 hour

60
Q

causes the fastest induction and emergence

A

desflurane

61
Q

leads to possible sympathetic response; increase in HR and BP ; most airway irritating pungent agent

A

desflurane

62
Q

advantages include: inert, low b:g coefficient (0.115), minimal cardiovascular effects, doesn’t trigger MH

A

xenon

63
Q

disadvantage of xenon

A

low potency (MAC 63%)

PMI (21 decks)

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