Inhalation Agents: MAC Flashcards

1
Q

the ideal inhaled anesthetic

A
  1. nonflammable
  2. easily vaporized at ambient temperature
  3. potent
  4. low blood solubility to assure rapid induction and recovery from anesthesia
  5. minimal metabolism
  6. compatible with epinephrine
  7. skeletal muscle relaxation
  8. suppresses excessive sympathetic nervous system activity
  9. not irritating to airways
  10. bronchodilation
  11. absence of excessive myocardial depression
  12. absence of cerebral vasodilation
  13. absence of hepatic and renal toxicity
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2
Q

effects of increased fluorination

A
  1. nonflammable
  2. decreased solubility ***
  3. decreased potency
  4. less toxic due to resistance to degradation
  5. decreased percentage metabolized
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3
Q

MAC is

A

minimum alveolar concentration (partial pressure) of an inhaled agent at 1 atmosphere that prevents skeletal muscle movement in response to a noxious stimulus in 50 percent of patients (ED50, potency)

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4
Q

____ greater concentration than MAC produces immobility in ___ of patients

A

10-30%

90-95%

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5
Q

what portion of the central nervous system determines MAC

A

spinal cord

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6
Q

____ is decreased resulting in immobility

A

spinal cord

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7
Q

perfusion of the brain alone with ordinary concentration does not produce ____

A

immobility (took up to 3-6X MAC)

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8
Q

use minimal alveolar concentration because alveolar reflects

A

the concentration at the cord or the brain most accurately

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9
Q

with alveolar concentration you must allow

A

for equilibration (generally about 10-15 min)

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10
Q

alveolar concentration is dependent on

A

agent (3-4 time constants)

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11
Q

as age increase, MAC

A

decreases 6% per decade

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12
Q

___ decreases MAC in all ages, but more so in the elderly

A

nitrous oxide

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13
Q

MAC is greatest in patients

A

less than a year of age

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14
Q

MAC decreases in nearly

A

50% in the elderly years

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15
Q

MAC from greatest to least

A

infants > children > neonates > adults

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16
Q

60% nitrous oxide causes about a ____ reduction in MAC normally

A

60%

more so in elderly

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17
Q

____ reduction causes MAC reduction

A

body temperature

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18
Q

MAC of desflurane is decreased almost in half by

A

a 10 degree C decrease in temp

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19
Q

MAC of ___ is not affected by body temperature

A

nitrous oxide

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20
Q

pregnancy decrease MAC due to

A

increased concentrations of progesterone

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21
Q

MAC decreases ___ through early postpartum and normalizes within ___

A

30%

12-72 hours

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22
Q

decreased CNS ___ decreases MAC

A

Na

23
Q

possible causes of decreased CNS Na leading to decreased MAC

A

dehydration, absorption of irrigant

24
Q

drugs that decrease MAC

A
  1. opioids
  2. benzodiazepines
  3. barbiturates and propofol
  4. acute ETOH injection
  5. local anesthetics
  6. nitrous oxide
  7. clonidine and dexmedatomidine
  8. some beta-blockers
  9. some calcium-channel blockers
  10. adenosine
25
Q

opioids have a ___ effect on MAC

A

ceiling

26
Q

benzodiazepine decrease in MAC is

A

dose-dependent

27
Q

the local anesthetic ___ IV decreases MAC

A

lidocaine

28
Q

nitrous oxide effects on MAC

A

0.5 MAC of N2O plus 0.5 MAC of isoflurane are additive to 1 MAC of either drug alone

29
Q

clonidine and dexmedetomidine decrease MAC by

A

decreasing central nervous system catecholamines and by hyperpolarization of CNS cell membranes

30
Q

factors that decrease MAC

A
  1. neuraxial opioids
  2. PaO2 < 38 mmHg
  3. BP < 40 mmHg
  4. cardiopulmonary bypass
31
Q

factors that increase MAC

A
  1. red hair
  2. drug induced increases in CNS catecholamine levels
  3. hyperthermia
  4. hypernatremia
32
Q

red hair increased MAC due to

A

excess pheomelanin production (19%)

33
Q

drugs that increase MAC

A
  1. cocaine
  2. ketamine
  3. amphetamines
34
Q

factors that do not alter MAC

A
  1. gender
  2. duration of anesthesia (isoflurane decreases)
  3. body mass
  4. arterial PaO2 > 50 mmHg
  5. atrial PaCO2 < 80 mmHg
  6. Hct > 10%
  7. BP > 40 mmHg
35
Q

MACawake is

A

the average of the concentrations immediately above and below those permitting voluntary response to command

36
Q

MAC__ usually exceeds MAC___

A

awake

amnesia

37
Q

MACawake is affected by

A

age (decreases) and inhalation agent

38
Q

the ratio of MACawake/MAC is not affected by

A

age as both decrease

39
Q

for desflurane, isoflurane, and sevoflurane, MACawake is

A

about 1/3 of MAC

40
Q

for halothane, MACawake is

A

more than 50% of MAC

41
Q

for nitrous oxide, MACawkae is

A

more than 60% of MAC

42
Q

the higher the MACawake/MAC ration, the __ the recovery

A

faster

43
Q

the higher the MACawake/MAC ration, the poorer the

A

amnestic value

44
Q

___ minimally affect MACawake

A

low dose opioids

45
Q

low dose opioids ___ the MACawake/MAC ratio so, __

A

increases

awakening should be more quickly

46
Q

MACawake does not ensure return of

A

esophageal sphincter tone or return of pharyngeal function

47
Q

concentration of inhaled agent may require levels of __ for patient safety

A

less than 0.1 MAC

48
Q

MAC TE

A

MAC to allow tracheal stimulation (intubation)

49
Q

to allow tracheal stimulation there needs to be:

A
  1. no coughing or bucking during suctioning of pharynx
  2. no movement or coughing within 1 min of extubation
  3. no breath holding or larygnospasm after extubation
50
Q

MAC TE is __ or __ MAC

A

equal to or exceeds MAC

51
Q

MAC bar

A

minimum alveolar concentration that blocks autonomic response to surgical stimulus

52
Q

MAC bar with 60% nitrous oxide for deflurane

A

1.3 MAC (1.9 MAC total)

53
Q

MAC bar with 60% nitrous oxide for isoflurane

A

1.3 MAC (1.9 MAC total)

54
Q

MAC bar with 60% nitrous oxide for sevoflurane

A

2.2 MAC