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Anes. Pharm. Me > Inhaled Anesthetics > Flashcards

Inhaled Anesthetics Flashcards

2
Q

The depth of general anesthesia depends on partial pressure exerted by inhalational agent in the patient’s brain. This brain P depends on _______ partial pressure which depends on _________ partial pressure which depends on partial pressure of agent in the inspired gas.

A

ArterialAlveolar

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3
Q

What is the path an inhalational agent takes from the vaporizer to the brain?

A

Vaporizor->circuit->Lungs->Blood->Brainand then it goes back out

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4
Q

What is Relative affinity of an anesthetic for two phases and therfore the Partitioning of that anesthetic between the two phases is called…

A

Solubility

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5
Q

In a mixture of gases, each gas has a ______ ______ which is the pressure which the gas would have if it alone occupied the volume.

A

Partial pressure

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6
Q

What factors can we change to influence the amount of Inspired agent?

A

increase concentrationIncrease FGF(decrease the volume of the circuit and decrease the absorption by the machine are also listed but these are difficult to change)

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7
Q

What is a formula that describes alveolar partial pressure?

A

Input into alveoli - uptake into blood

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8
Q

How can we increase PA?

A

Increase ventilationIncrease concentration

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9
Q

What are two ways to increase initial concentration and uptake?

A

Concentration effectSecond gas effect

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10
Q

What is the definition of concentration effect?

A

Impact of the inspired partial pressure of the agent increases the rate of rise of the partial pressure of the alveolus(the higher the concentration of gas used the faster the alveolar concentration of that gas….or…. At 100 percent inspired concentration, the uptake of anesthetic creates a void, which draws gas down the trachea. This additional inspiration replaces the gas taken up.)

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11
Q

what is the second gas effect

A

High volume of uptake of one gas accelerates the rate of increase of the PA of the companion gas(During induction of general anesthesia when a large volume of nitrous oxide is taken up from alveoli into pulmonary capillary blood, the concentration of gases remaining in the alveoli is increased.)

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12
Q

What three factors affect anesthetic uptake?

A

Solubility, cardiac output, alveolar-venous difference

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13
Q

What is the formula for uptake?

A

Uptake = soulbility x CO x (PA-PV)

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14
Q

RElative affinity of inhale anesthetic for two phases at equilibrium?

A

Solubility

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15
Q

What happens to ithe PA/PI rise if soulbility is increased? How would this affect induction?

A

decreases PA/PI making induction slower, Halothane is given as the example for this

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16
Q

Rank the Partition coefficients from lowest to highest of Halothane, Sevoflurane, Desflurane, Nitrous Oxide and Isoflurane.

A

Desflurane (0.42)<Halothane (2.4)

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17
Q

The more soluble an anethesthetic agent is in the blood, the _____ the drug goes into the body, and the ________ the patient becomes anesthetised.

A

FasterSlower

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18
Q

How can you compensate for a more soluble agent to speed induction?

A

YOu can increase concentration, but it there are limits

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19
Q

Increased cardiac output has what effect on the rate of rise in PA/PI?

A

decreases

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20
Q

Increased cardiac output is more a concern for (soluble/insoluble) agents.

A

soluble. ON insoluble agents there is less of an effect

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21
Q

How does cardiac output influence its effect on uptake?

A

greater pulmonary blood flow remove more anesthetic and lowers PA. the alveoli will saturate faster if it is seeing less blood flow

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22
Q

What is responsible for alveolar venous difference?

A

absorption by the tissues

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23
Q

If gases were not absorbed by tissue what would the arterial venous difference be?

A

0

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24
Q

What affects the tissue uptake of anesthetic gases?

A

Tissue solubilityTissue blood flowDifference between partial pressure of blood and the specific tissue

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25
Q

Why do muscle and fat take longer for uptake and washout of gases compared to VRG?

A

Less blood flow (VRG is 10% of body mass and receives 75% of bf, whereas fat is 20% and receives only 6% of bf)

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26
Q

How do we get rid of anesthetic gases?

A

biotransformation (small amount)transcutaneous lossEXHALATION

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27
Q

Which agent is the most metabolized?

A

Halothane

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28
Q

Which agent is the least metabolized?

A

Nitrous

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29
Q

Is there a concentration effect for elimination?

A

no

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30
Q

What are the partial pressures in the tissue during recovery?

A

All tissues have varying amounts

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31
Q

What changes pharmacokinetics of inhalational agents?

A

AgeLean muscleBody fatHepatic functionPulmonary gas exchangCardiac output

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32
Q

What MAC prevents movement in 95% of the population?

A

1.3

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33
Q

how does MAC change per decade?

A

6% decrease per decade

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34
Q

What is the definiton of MAC awake?

A

end tidal concentration of an anesthetic agent at which 50% of patients appropriately respond to verbal commands. It only applies to inhalation agents. ~10% of MAC

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35
Q

What may affect MAC awake?

A

Adjuctive needsagehypothermiaSedatives

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36
Q

What is MAC bar?

A

concentration required to block autonomic reflexes to nociceptive stimuli. 1.3 MAC

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37
Q

What factors increase mac?

A

HyperthermiaDrug-induced increase in catecholaminesHypernatremia

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38
Q

How does chronic alcohol abuse affect MAC?

A

no change

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39
Q

What are some factors that may decrease MAC?

A

OPIOIDSAcute alcohol intoxicationPregnancyLithiumNeuraxial opioidsOthers:Pre op medsincreased ageHypothermiaA-2 agonistsPaO2<40

40
Q

Which inhaled anesthetics were available in 1840s?

A

Nitrous oxideEther Chloroform

41
Q

Which anesthetics became available in 1951?

A

Halothanefloroxene

42
Q

When did isoflurane become available? Des? Sevo?

A

1981, 1992 and 1994

43
Q

how do anesthetic gases affect cerebral blood flow?

A

Increase vasodilation, decrease vascular resistance, increase CBF and ICP

44
Q

Which causes more CBF, halothane or isoflourane?

A

Halothane can increase CBF by 166%d

45
Q

What are inhaled anesthetics effect on siezures?

A

They will block siezure activity

46
Q

What is burst suppression for isoflorane?

A

1.5 MAC. This will sacrifice blood pressure. all volatile agents cause burst supression at >2 MAC

47
Q

what effect do inhaled anesthetics have on CSF production?

A

Sevo at 1 MAC may depress CSF production by up to 40%

48
Q

Which hair color is associated with an increased mac?

A

red

49
Q

what is the maximum for inhaled anesthetics for Evoked potential?

A

.5 MAC

50
Q

How do inhaled anesthetics affect EEG

A

all may abolish EEG activity

51
Q

How do inhaled anesthetics affect Cerebral blood flow?

A

All cause it to increase

52
Q

HOw do Inhaled anesthestics affect Intercranial pressure?

A

Increased in all. Halogenated agents may increase it or remain the same

53
Q

HOw do Inhaled anesthestics affect Cerebral perfusion pressure?

A

Nitrous oxide will decrease, all others increase

54
Q

HOw do Inhaled anesthestics affect cerebral metabolic demands?

A

Nitrous increase all others decrease

55
Q

HOw do Inhaled anesthestics affect CO2 reactivity?

A

No change

56
Q

What effects do volatiles have on SVR and BP

A

Decrease SVR and BP

57
Q

What effect do nitrous have on BP?

A

No change or slight increase

58
Q

What effect do desflurane have on HR?

A

Causes tachycardia (and may cause HTN) due to stimulation of SNS

59
Q

How do Iso and Sevo cause an increase in HR?

A

baroreceptor mediated

60
Q

What effects do volatile have on CO?

A

decrease

61
Q

What effect does Nitrous have on CO?

A

slight increase due to sympathomimetic activity

62
Q

HOw do volatiles affect PVR?

A

decrease

63
Q

what is coranary steal? which agent is associated with it and why?

A

Coronary steal is the diversion of blood from a myocardial bed with limited or inadequate perfusion to a bed with more adequate perfusion. Isoflurane has been associated with this because it is a potent coronary vasodilator (why the others are weak coronary vasodilators). However, no studies demonstrate an increas in ischemia with the use of ISO

64
Q

what happens with administering halothane with epinephrine?

A

May cause arrhythmias

65
Q

How do inhaled anesthetics affect MAP?

A

Nitrous remains the same or increases. All others decrease

66
Q

How do inhaled anesthetics affect systemic vascular resistance?

A

Nitrous increases. Other decrease, except sevo stays the same

67
Q

How do inhaled anesthetics affect Heart rate?.

A

Increase

68
Q

How do inhaled anesthetics affect Miocardial function?

A

all decrease

69
Q

How do volatile agents affect Vt, RR and MV?

A

RR increases, Vt and MV decrease–rapid shallow breathing

70
Q

at what MAC do des and Sevo produce apnea?

A

1.5-2 MAC

71
Q

How do volatile drugs affect AW resistance? Which is the exception?

A

Decrease AW resistance, except Des

72
Q

HOw does anesthesia affect FRC?

A

decreases

73
Q

HOw do inhaled anesthetics affect the kidneys?

A

decrease renal blood flow, GFR and urine output. May also lead to nephrotoxicity

74
Q

How do the inhaled anesthetics affect the liver?

A

decrease hepatic blood flow and clearance, and can cause hepatic toxicity

75
Q

What effects do inhaled drugs have the uterus?

A

decrease uterine smooth muscle contractility and blood flow.helpful to remove retained placentaMay increase blood loss during delivery

76
Q

Can inhaled drugs cross the placenta?

A

Yes

77
Q

What effects do inhaled drugs have on skeletal muscle?

A

Ether derived drugs pruduce muscle relaxation and potentiate paralyticsNitrous does not produce relaxation and may produce rigidity

78
Q

How do volatile anesthetics lower body temp?

A

Lower the core temp set point at which thermoregulatory vasoconstriction is activatedVasodilation redistributes blood flow from central to peripheral compartmentsMetcabolic oxygen consumption is decreased-decreases heat generation

79
Q

Which produces more compound A? baralyme or soda lime?

A

Baralyme

80
Q

Which volatile agent leads to carbon monoxide?

A

Des–from dry dessicated absorber

81
Q

What leads to nephrotoxicity from volatiles/

A

an inactive flouride metabolite–methoxyflurane

82
Q

What are the two types of halothane hepatitis?

A

Mild self limiting form and a more rare life threatening hepatic necrosis

83
Q

what % of halothane is metabolized by liver?

A

20%

84
Q

What is the preservative used with halothane?

A

thymol

85
Q

how much of Isoflurane is metabolized?

A

0.2%

86
Q

Isoflurane has ____ cardiovascular changes at 1 MAC

A

minimal

87
Q

Why is isoflurane a good choice for EEG?

A

2 MAC = isoelectric EEG

88
Q

What patient should you avoid use of Des?

A

reactive Airways

89
Q

Is des used with LMA?

A

No–AW irritant

90
Q

Which volatile agent is least AW irritant?

A

Sevo

91
Q

HOw much is Sevo metabolized?

A

2-5%. Associated with Compound A formation and renal tubular injury

92
Q

What is the rule for sevo at low flows?

A

you can use low flows for 2 MAC hours

93
Q

How does nitrous affect PVR?

A

increases

94
Q

How does Nitrous affect CMRO2?

A

Increases

95
Q

When shoudl nitrous be avoided?

A

enclosed air spaces–34x as soluble as nitrogenAvoid with: laparoscopic surgeryWorking on bowelsEye surgery with the gas buble

Anes. Pharm. Me (15 decks)

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