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Pharmacology > Inhaled Agents #3 > Flashcards

Inhaled Agents #3 Flashcards

1
Q

Are the cardiac effects the same or different between the various inhaled agents?

A

Equal concentrations of inhaled anesthetics have similar circulatory effects

At 1 MAC all agents will have similar cardiac effects. At 0.5 MAC, all agents will have same effect

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2
Q

MAP increases or decreases with in increase in concentration of des, sevo, and iso.

Why?

A

MAP decreases

This is due to a decrease in SVR (vessels dilate)

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3
Q

Why does MAP decrease with halothane?

A

MAP decreases by decrease in CO

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4
Q

How does N2O affect MAP?

A

It’s unchanged or mildly increased

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5
Q

How can you help decrease the agents effects on MAP?

A

Use N2O with the agent

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6
Q

HR response occurs at ___________ concentrations for each agent

A

Unique

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7
Q

How does Forane (iso) affect HR?

A

Starting at 0.25 MAC, a linear, dose depends increase in HR is observed

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8
Q

How does desflurane affect HR?

A

Minimal increase in HR at concentrations < 1 MAC

At concentrations >/= 1 MAC, a linear dose dependent increase in HR is observed

*usually see increase in HR the most with des. Usually seen during induction . If you take a slower induction sequence with des. If have a total combined of des x flows > 24, will see increased HR. If want des at 8, have FGF at 3 or less, won’t see HR increase.

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9
Q

How does sevoflurane affect HR?

A

HR does not increase until concentrations > 1.5 MAC

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10
Q

Cardiac Index is __________ influences by inhalation agents

A

Minimally

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11
Q

Which agents produces a minor increase in EF compared with awake measurements?

A

Desflurane

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12
Q

At concentrations ____________ MAC, desflurane does not increase HR or MAP

A

< 1

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13
Q

Plasma concentrations of what 2 things are increased with these surges in sympathetic nervous system activity

A

Epi and Norepinephrine

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14
Q

If you abruptly increase ___________ or ___________ will see sympathetic surge and see increase in HR.

A

Iso and des

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15
Q

Circulatory stimulation is not observed with the abrupt increase in what agents up to 2 MAC

A

Sevoflurane
Halothane
Ethrane

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16
Q

T/F: inhaled agents predispose the heart to PVCs

A

False

Prolong effective refractory period

Newer drugs don’t really cause PVCs except at higher doses

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17
Q

What agents does sensitize the heart to PVCs?

A

Halothane

Due to catecholamine release and hypercarbia

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18
Q

Inhaled agents do what to QT interval

A

They prolong the QT interval

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19
Q

What agent do you want to avoid in pts with known congenital long QT syndrome (LQTS)?

A

Sevoflurane

Safe if on a beta blocker therapy

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20
Q

What other drug commonly used by anesthesia will prolong QT interval?

A

Zofran

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21
Q

If pt has known CAD, are inhaled agents or IV anesthetics better?

A

No data effectively demonstrates a difference in outcomes between inhaled and IV opioid anesthesia

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22
Q

Which agent causes coronary steal?

A

Isoflurane

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23
Q

What is coronary steal?

A

Forane’s ability to dilate small-diameter coronary arteries might cause a susceptible pt to developer regional myocardial ischemia as a result of coronary vasodilation

*not found valid

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24
Q

T/F: volatile anesthetics exert a protective effect on the heart.

A

True

They limit the area of myocardial injury and preserve function after exposure to ischemic insult

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25
Q

What is ischemic preconditioning?

A

Protective benefits of volatile anesthetics against myocardial ischemia in setting of compromised regional perfusion

if can get heart prepared for ischemic event, it won’t affect it as much

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26
Q

What are the 2 periods of protection of ischemic preconditioning.

A

First period
-1-2 hours after the conditioning episode

Second period
-benefit reappears 24 hours later and can last as long as 3 days

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27
Q

What is the crucial event that confers the protective activity of ischemic preconditioning?

A

The opening of mitochondrial adenosine triphosphate (ATP)- sensitive potassium channels

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28
Q

What happens to respiratory rate and tidal volume as anesthetic concentration increases?

A

Respiratory rate increases and tidal volume decreases

Minute ventilation is relatively preserved

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29
Q

We are concerned with tachycardia in what pts?

A

Elderly
Previous stents
Previous cardiac events
Risk factors such as obesity, DM, HTN

30
Q

What do you need to be concerned about with pt with chronic HTN?

A

They bc more hypotensive bc they have less inter-vascular volume

31
Q

T/F: gas exchange becomes left efficient as anesthetic depth increases

A

True

Decreased TV leads to greater dead space ventilation relative to alveolar ventilation

32
Q

If you don’t assist with ventilation, what will happen to PaCO2 as anesthetic depth increases?

A

PaCO2 increases proportionate to anesthetic depth

33
Q

Dose related ___________ of the respiratory response to increasing CO2

A

Blunting

*decreased respiratory drive

34
Q

Ventilatory stimulation response evoked by arterial hypoxemia is __________ by volatile anesthetics

A

Blunted

35
Q

The diaphragm is displaced_________, and __________ displacement of rib cage occur from __________ expiratory muscle activity. The result is a __________ in FRC.

A

Cephalad

Inward

Enhanced

Reduction

36
Q

T/F: inhalation agents have a limited effect on the principle of “hypoxic pulmonary vasoconstriction”

A

True

37
Q

In the absence of bronchoconstriction, bronchodilating properties of inhalation agents are _________

A

Limited

*if no spasm, won’t do much. If bronchospasming, will help

38
Q

What are some things that can occur from pungency of inhaled anesthetics?

A

Coughing
Breath-holding
Laryngospasm
Arterial oxygen desaturation

More irritating to smokers and pts with asthma. Smokers will cough more
*all agents irritate the airway

39
Q

What are the most pungent agents?

A

Desflurane

Forane

40
Q

What agents are nonpungent?

A

Sevoflurane

Halothane

Nitrous Oxide

41
Q

Inhalation agents ______ CMRO2

A

Decrease

CMRO2: cerebral metabolic rate of oxygen

42
Q

In normocapnic pts, cerebral vasodilatation occurs at concentrations above _________ MAC

A

0.6

Can be good to deliver more blood to the brain, can be bad if having issues with ICP

43
Q

Explain the biphasic dose-dependent effect on cerebral blood flow

A
  • At 0.5 MAC, the decrease in CMRO2 offsets the vasodilatation such that cerebral blood flow does not change significantly
  • At concentrations >/= 1 MAC, vasodilating effects predominate and cerebral blood flow increases, especially if the systemic BP is maintained at awake values
  • be careful in pts with elevated ICP
44
Q

What effects does nitrous oxide have on the CNS?

A

*avoid in pts with cerebral events

  • causes cerebral vasodilation
  • increases CMRO2
  • coadministration of opioids, barbiturates, or propofol (not ketamine) counteract these effects
45
Q

ICP ____________ with all volatile anesthetics at doses ___________

A

> 1 MAC

*pts with high ICP or head trauma, keep below 1 MAC

46
Q

Autoregulation is impaired at concentrations _________

A

< 1 MAC

At higher concentrations, everything is dilated and unable to auto regulate (tissues can’t adjust flow to maintain good MAP)

47
Q

What are evoked potentials?

A

SSEP, MEP, BEP, VEP…..

Measuring the signals either peripheral to brain or brain to periphery

48
Q

How do volatile anesthetics and N2O affect evoked potentials?

A

They depress the amplitude and increase the latency of SSEP in a dose-dependent manner

they are looking for the same thing that our anesthetics cause

49
Q

Evoked potentials may be abolished at _______ MAC

A

1

50
Q

N2O and _________ MAC inhalation also abolish EP

A

0.5

51
Q

Low concentrations ________ MAC decrease the reliability of motor evoked potentials

A

0.2-0.3

52
Q

Increase depth of anesthesia is characterized by ___________ amplitude and __________ on the EEG

A

Increased

Synchrony

53
Q

Burst suppression (periods of electrical silence) occur at ________ frequency as depth of anesthesia __________

A

Greater

Increases

54
Q

This isoelectric pattern predominates at ___________ MAC

A

1.5-2.0

Means no brain activity

55
Q

What agent may be associated with epileptiforom activity on the EEG, especially in high concentrations

A

Sevoflurane

In pts with Hx of seizures better to not use.

56
Q

Inhalation agents produce a dose dependent skeletal muscle ________ and __________ the activity of neuromuscular blocking drugs.

A

Relaxation

Enhance

57
Q

Elimination of volatile anesthetic agent enhances the recover from what type of medication?

A

Neuromuscular blockade

58
Q

What agents can potentially trigger MH?

A

All potent inhalation anesthetics

Halothane>isoflurane>sevoflurane>desflurane

59
Q

What are some hepatic effects of inhaled agents?

A

Immune mediated liver injury

  • may follow anesthesia by inhaled agents
  • massive hepatic neurosis that leads to death or requires transplant
  • rare

Mild liver injury

  • can occur with halathane
  • more likely to occur after decreased hepatic blood flow and reduced O2 deliver to liver

Halothane hepatitis
-not true hepatitis, just liver injury

60
Q

Will you still give volatile agents to a pt with pre-existing liver disease not related to anesthesia?

A

Yes

61
Q

This produces inorganic fluoride which caused sporadic incidence of nephrotoxicity and high output renal failure after prolonged anesthetic

A

Methyoxyflurane

62
Q

This is produced from the breakdown of sevoflurane and halothane and is nephrotoxic after prolonged exposure

A

Compound A

63
Q

This inactivates methionine synthase, the enzyme that regulates vitamin B12 and folate metabolism.

A

Nitrous Oxide

Avoid in pts with pre-existing vitamin B12 deficiency or underlying critical illness

64
Q

Blood gas partition coefficient of N2O

Blood gas partition coefficient of nitrogen

A

0.46 —>34 times greater than nitrogen

Nitrogen 0.014

Can cause volume/pressure of air-filled cavities to increase

*N2O will expand gas space faster than Nitrogen can leave space

65
Q

Degradation of CO2 absorbent is an endothermic or exothermic process

A

Exothermic

May cause extremely high temps inside the CO2 absorber canister

66
Q

What accelerates degradation of soda lime?

A

High fresh gas flows

67
Q

What do iso and des produce when exposed to desiccated absorbent?

A

Carbon monoxide

68
Q

T/F: variable bypass vaporizers are temperature compensated

A

True

69
Q

What is the vapor pressure of desflurane at sea level at 20 degrees C

A

700mmHg

Delivery by a variable bypass vaporizer can produce unpredictable concentrations ->use specially designed vaporizer

70
Q

Tec 6 vaporizer heats desflurane to ___________ of pressure

A

2 atmospheres

*does not altitude adjust. At higher altitudes, pp of des will be lower and lower concentration will be delivered to pt

Pharmacology (4 decks)

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