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Pharmacology Sem 1 > Inhaled Agents Part 2 > Flashcards

Inhaled Agents Part 2 Flashcards

1
Q

When is Ether day?

A

October 16, 1846

WTG Morton successfully demonstrates the use of ether in the removal of a jaw tumor at Mass Gen

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2
Q

Fresh gas flow is determined by

A

the vaporizer and flowmeter settings

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3
Q

Fractional inspired gas concentration is determined by

A

FGF rate, breathing-circuit volume and machine absorption

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4
Q

Fractional arterial gas concentration is affected by

A

ventilation/perfusion mismatching

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5
Q

Fractional alveolar gas concentration is determined by

A

uptake, ventilation, and the concentration effect and second gas effect

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6
Q

The Fi/FA ratio is a

A

gas to gas ratio

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7
Q

Factors that affect inspiratory concentration include

A

fresh gas flow, breathing system volume, & machine absorption

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8
Q

Factors affecting alveolar concentration include

A

blood solubility of the agent, alveolar blood flow, partial pressure between alveoli and venous blood

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9
Q

If Fa is less than the end-tidal level it is possible that

A

venous admixture, alveolar dead space, or non-uniform distribution exists

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10
Q

Ventilation/perfusion mismatch can occur in a situation such as

A

right bronchial intubation

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11
Q

The overall effect for V/Q mismatch is

A

increase in alveolar partial pressure (highly soluble agents) and decrease in arterial partial pressure (low solubility agents)

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12
Q

What is the mechanism of action of inhaled gases?

A

unknown
possible targets may include: NMDA receptors, Tandem pore potassium channels, voltage-gated sodium channels, glycine receptors, & GABA receptors

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13
Q

What is the Meyer Overton Theory?

A

liphophilicity equates to potency

this is not absolute though

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14
Q

What are the CNS effects of inhaled gases?

A

CMRO2 is decreased

cerebral blood flow is increased (dose-dependent)

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15
Q

What does “uncoupling” mean?

A

describes the phenomenon of a decrease in CMRO2 but an increase in cerebral blood flow
greater with sevoflurane

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16
Q

What does nitrous oxide do to the brain?

A

increases both CMRO2 and CBF
mild hyperventilation helps attenuate increases in
CBF

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17
Q

Clinically relevant doses of inhalational agents preserve this when ICP is a concern, mild hyperventilation 30-35 mmHg

A

cerebral vascular responsiveness to CO2

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18
Q

What is the effect of inhalational agents on evoked potentials?

A

inhalational agents decrease amplitude and increase latency

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19
Q

EEG and evoked potentials

A

inhalational agents produce a dose-related suppression

burst suppression occurs at: 1.5 MAC of desflurane & 2 MAC with isoflurane and sevoflurane

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20
Q

For neonates having surgery,

A

there is a concern for developmental neurotoxicity
it was demonstrated in rodents and non-human primates that they cause activation of extrinsic and intrinsic apoptotic cell death pathways

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21
Q

When giving gas to neonates it is recommended that

A

keep surgery as short as possible

use short acting medications and multimodal approaches

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22
Q

All volatile inhalation agents reduce

A

cardiac output and index in a dose-dependent fashion

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23
Q

Volatile agents and nitrous oxide induce HR changes via

A

SA node antagonism
modulation of baroreflex activity
sympathetic nervous system activity

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24
Q

Reduced MAP secondary to

A

SVR reduction

nitrous oxide used in combination with anesthetics reduces this

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25
Q

Reduced cardiac output is caused by

A

reduction in free intracellular Ca2+ contractil state

As MAC hours increase, there is slight increase of CI and HR

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26
Q

Emergence delirium in children

A

is more common with sevoflurane and desflurane

& can cause injury & delay discharge

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27
Q

Emergence delirium in children can be prevented by

A

having a quiet, stress-free environment and giving medication adjuncts

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28
Q

Postoperative cognitive dysfunction is of

A

great concern in the elderly

there is no clinically significant association between major surgery and anesthesia with long-term POCD

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29
Q

Nitrous oxide causes a slight increase in

A

PVR and it worsens in patients with pulmonary hypertension

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30
Q

The volatile agents affect pulmonary circulation

A

by decreasing pulmonary artery pressure

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31
Q

Gases are able to affect the pulmonary circulation by

A

mildly depressing hypoxic pulmonary vasoconstriction

isoflurane has the greatest effect

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32
Q

All inhalational agents produce some

A

vasodilation (SVR)

in hypotensive patients this can result in a ‘reverse-Robin Hood’ syndrome (isoflurane)

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33
Q

Preconditioning is

A

a phenomenon in which the heart is exposed to a cascade of intracellular events that protect it from ischemic and reperfusion insult

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34
Q

Sensitization is

A

when volatile agents reduce the quantity of catecholamines necessary to evoke arrhythmias
Less common in ASA I & II classifications

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35
Q

The CO, SVR, MAP, and HR in isoflurane:

A

CO: decreased
SVR: decreased
MAP: decreased
HR: increased

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36
Q

The CO, SVR, MAP and HR in desflurane:

A

CO: —
SVR: decreased
MAP: decreased
HR: increased

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37
Q

The CO, SVR, MAP, and HR in sevoflurane:

A

CO: –
SVR decreased
MAP: decreased
HR: no change

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38
Q

The CO, SVR, MAP, and HR in nitrous oxide:

A

CO: decreased
SVR: increased
MAP: no change
HR: increased

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39
Q

The CO, SVR, MAP, and HR in xenon is:

A

CO: no change
SVR: no change
MAP: no change
HR: decreased

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40
Q

The gases do what to the airways?

A

relax airway muscle and produce bronchodilation

41
Q

Volatile agents cause dose-dependent decreases in (respiratory related)

A

tidal volume- compensated by increase in RR (but not sufficient to offset TV)
Responsiveness to carbon dioxide
-increases apneic threshold
-exacerbated by co-administration of an opioid

42
Q

What volatile agent has the potential to impair hepatic function?

A

Halothane
halothane hepatitis (rare)
caused by trifluoracetyl-containing metabolites binding to proteins and forming antibodies
re-exposure of the patient to halothane cause massive hepatic necrosis

43
Q

What gas was historically associated with increased production of haloalkene, compound A?

A

sevoflurane
This occurs with the use of older absorbents (CaOH or lithium OH)
newer agents (NaOH and KOH do not have this issue
should not exceed 2 MAC hours at flows <2L per minute
Fresh gas flow <1 L per minute not recommended

44
Q

Autoregulation of renal circulation remains relatively intact

A

decrease in renal SVR leads to decline in GFR
ultimately a decrease in urine output
desflurane has least impact on renal function

45
Q

Action of volatile agents on hepatic function

A

possible impairment although extremely rare
sevoflurane undergoes the greatest metabolism (5-8%)
however it does not cause hepatic toxicity

46
Q

Neuromuscular effects of volatile agents include

A

dose-dependent relaxation on skeletal muscle
additive effect on non-depolarizing NMBDs
delays recovery from non-depolarizing NMBDs

47
Q

The ideal anesthetic agent properties:

A

non-irritating to the respiratory tract, rapid induction and emergence, chemically stable (non-flammable), produce amnesia analgesia and areflexia, potent, not metabolized and excreted by respiratory tract, free of toxicity and allergic reactions, minimal systemic changes, uses a standardized vaporizer, affordable

48
Q

The four properties that affect how agents work include

A

vapor pressure, boiling point, partial pressure, and solubility

49
Q

Boiling point is

A

the temperature at which vapor pressure exceeds atmospheric pressure in an open container

50
Q

Vapor pressure is

A

the pressure exerted inside a container between liquid and vapor
at room temperature, most volatile agents have a
vapor pressure below atmospheric pressure
it is directly proportional with temperature

51
Q

The partial pressure is

A

fraction of pressure within a mixture (Dalton’s Law)

52
Q

Solubility is

A

the tendency of a gas to equilibrate with a solution (Henry’s Law)
anesthetic gases administered to the lungs diffuse into the blood until the partial pressures of the alveoli and blood are equal

53
Q

The concentration of anesthetic in tissue is dependent on

A

the partial pressure and solubility

54
Q

For most drugs, concentration is measured as

A

mass (mg/mL) but it can be expressed in percent by weight or volume

55
Q

Gas is expressed as

A

a fractional concentration

fractional volume= Panesthetic/Patmospheric

56
Q

MAC awake is

A

the MAC in which 50% of the populations opens eyes to command

57
Q

MAC ‘BAR’

A

the MAC necessary to block adrenergic response to stimulation
usually 1.3 of MAC value
can be reduced by administering a narcotic prior to incision

58
Q

MAC requirements decrease with age

A

age
6% decline (of a normal MAC) each decade after the age of 40
MAC relatively unaffected by gender, duration of anesthesia, comorbidities

59
Q

The additive effect

A

0.5 MAC of nitrous oxide + 0.5 MAC of isoflurane= 1 MAC sevoflurane
the idea that giving nitrous can decrease the MAC requirement of another gas but make it as effective as 1 MAC of another agent

60
Q

Vaporizers are

A

calibrated for specific agents

61
Q

The vaporizer facilitates the movement of anesthetic from the machine to the patient through

A

fresh gas flow, pressure, and temperature

62
Q

What is the chemical structure of isoflurane?

A

halogenated methyl ethyl ether

63
Q

Isoflurane is the most ____ of the volatile agents

A

potent

slower onset and recovery from anesthesia

64
Q

Isoflurane affects CV by

A

minimal cardiac depression, preserves carotid baroreceptors

dilates coronary arteries; concern for ‘reverse-Robin-Hood’

65
Q

Isoflurane respiratory effects

A

pungent, not used for inhalational induction

tachypnea less pronounced

66
Q

Desflurane is the ____ _____ of the volatile agents

A

least potent
quicker induction and emergence
potential to boil at room temperature

67
Q

The cardiovascular effects of desflurane are

A

rapid increases in desflurane lead to increases in HR & BP

attenuated with fentanyl, esmolol, clonidine

68
Q

The respiratory effects of desflurane are

A

very pungent; can cause airway irritation, increased salivation, breath holding, coughing, laryngospasm
avoid in patients with reactive airway disease

69
Q

The chemical structure of sevoflurane

A

fluorinated methyl isopropyl ether

70
Q

Sevoflurane has moderate

A

potency and has rapid induction and emergence

71
Q

Sevoflurane is the preferred volatile for

A

inhalational induction because it is non-pungent

72
Q

Sevoflurane has the following CV effects:

A

may prolong QT interval

CO is less maintained than other volatile agents- HR not increased

73
Q

Sevoflurane is metabolized

A

in the liver

increases in inorganic fluoride ions but never shown to result in nephrotoxicity

74
Q

Soda lime can degrade sevoflurane

A

into Compound A
increased gas temperature, low flow anesthesia,
high sevoflurane concentrations and prolonged
surgeries (nephrotoxic in rats, not humans)
For safety: calcium hydroxide absorbent, flows 2 lpm, avoid in patients with renal dysfunction

75
Q

Nitrous oxide is

A

not a volatile anesthetic

it is colorless and odorless

76
Q

Nitrous oxide acts on

A

NMDA receptor antagonist which may lower risk for chronic pain after surgery

77
Q

A safety consideration of nitrous oxide is

A

it is nonexplosive and nonflammable however it does support combustion like oxygen

78
Q

Nitrous oxide has decreased in popularity because

A

chronic exposure can lead to inactivation of vitamin B12 cofactor for enzyme synthesis, disrupting DNA synthesis leading to teratogenic bone marrow and immunosuppression effects (don’t use on pregnant women in first two trimesters)

79
Q

Nitrous oxide has effects on the respiratory system including

A

increasing respiratory rate

decreasing hypoxic drive

80
Q

Nitrous oxide has effects on the cerebral system including

A

increases CMRO2 and CBF

81
Q

Nitrous oxide increases the risk of

A

PONV

82
Q

Nitrous oxide stimulates the

A

SNS, BP, HR, CO unchanged or slightly elevated

83
Q

Absolute contraindications to using nitrous oxide include

A

expansion of gas-filled space

methionine synthase pathway deficiency

84
Q

Relative contraindications of nitrous oxide include

A

PONV, first trimester of pregnancy, increased ICP, pulmonary HTN, prolonged surgery >6 hours

85
Q

Xenon is a

A

noble gas with known anesthetic properties

86
Q

Xenon works

A

through NMDA and glycine receptor binding sites

87
Q

Xenon has minimal

A

CV, hepatic, or renal effects and has no effect on the ozone layer

88
Q

Xenon violates the principle of ideal gases because

A

it is expensive and has limited availability (hard to extract)

89
Q

The BP, VP, blood:gas, oil:gas, MAC for sevoflurane

A

BP: 59, VP: 157, Blood gas: 0.65, Oil:gas 47, MAC 2.0

90
Q

The BP, VP, blood:gas, oil:gas, MAC for desflurane

A

BP: 24, VP: 669, Blood gas: 0.42, Oil:gas 19, MAC: 6.0

91
Q

The BP, VP, blood:gas, oil:gas, MAC for isoflurane

A

BP: 49, VP: 238, Blood:gas 1.46, Oil:gas 91, MAC 1.2

92
Q

The BP, VP, blood: gas, oil:gas, MAC for nitrous oxide

A

BP: -88, VP: 38,770, Blood gas: 0.42, oil:gas 1.4, MAC 104

93
Q

Malignant hyperthermia can be triggered by

A

volatile anesthetics, succinylcholine, and stress

94
Q

Malignant hyperthermia is due to

A

ryanodine receptor gene mutation (chromosome 19)

95
Q

Signs and symptoms of malignant hyperthermia include

A

increase in CO2 production, muscle rigidity, metabolic acidosis, high temperature (late sign)
also may see dark urine color, tachycardia, tachypnea

96
Q

The treatment for malignant hyperthermia is

A

dantrolene sodium- muscle relaxant
1 mg/kg (supplied in 70 mL vials containing 20 mg of Dantrolene, 3000 mg of Mannitol and sodium hydroxide)
administer until symptoms subside
up to 10 mg/kg

97
Q

Ryanodex is

A

a new IV formulation of dantrolene for the prevention and treatment of MH
shorter half-life
requires supplementation of mannitol
requires fewer dials and less reconstitution

98
Q

Anesthesia in pregnant patients

A

most common appendectomy, cholecystectomy, ovarian, or trauma

99
Q

For pregnant patients

A

elective surgery should be delayed until after delivery

Nonurgent surgery should be performed in the second trimester

Pharmacology Sem 1 (14 decks)

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