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Anesthesia Pharmacology > Induction Agents > Flashcards

Induction Agents Flashcards

1
Q

what is the pH of thiopental? Is it a good medium for bacteria?

A

10.5. No, too basic

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2
Q

How long is thiopental good for if it is in a refrigerator? Room temp?

A

indefinately if in the fridge. 7 days room temp

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3
Q

What are carbon 2 derivitives of thiopental useful for?

A

more useful as a sleep aid

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4
Q

What are carbon 5 derivatives of thiopental useful for?

A

anticonvulsant properties

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5
Q

Name 2 disadvantages of the high pH of thiopental?

A

burns when injected and when given with acidic drugs will form a precipitate. Therefore it may require a separate IV.

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6
Q

how is thiopental supplied?

A

anhydrous powder

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7
Q

what is the mechanism of action of thiopental?

A

Thiopnetal binds at the GABA site and at a distinct binding site at the GABAa receptor and increases the time the Choride channel is open.
Thiopental also decreases sympathetic transmission

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8
Q

Are barbituates lipid soluble?

A

Yes. High lipid solubility allows them to get into the brain quickly. UPtake in the brain takes place in 30 seconds

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9
Q

What percent of thiopentol is bound to protein in the blood stream.

A

80%

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10
Q

how long does redistribution of barbs take?

A

5-8 minutes

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11
Q

what is an IV induction dose of thiopental?

A

3-5 mg/kg (Jenn said she didn’t care if we know this number)

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12
Q

What is the onset and duration of thiopental?

A

onset: 30-40 seconds with a peak at 1 minute and duration of 5-8 minutes

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13
Q

Where is thiopental metabolized? Is this a fast or slow process?

A

metabolized relatively slowly by the liver. this can lead to the “hangover”

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14
Q

Does thiopental have active metabolites?

A

yes–pentobarbital

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15
Q

how is thiopental eliminated?

A

renal

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16
Q

Which is metabolized faster: thiopental or methohexital?

A

Methahexitol

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17
Q

What are the clinical uses of barbituates?

A

Induction of anesthesia and treatment of increased ICP

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18
Q

How do you calculate cerebral perfusion pressure?

A

MAP - ICP (CVP can be substituted for ICP if you don’t have an ICP monitor) normal value is 80-100 mm Hg

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19
Q

Which receives more blood flow white or gray matter?

A

Gray matter performs the cortical activity and receives 80% of the blood flow. White matter is more associated with structural integrity and receives 20% of blood flow

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20
Q

How much can the metabolism of the brain we suppress with anesthesia?

A

60% of the brain’s energy consumption is associated with electrophysiological function. This can be suppessed. The remaining 40% is for homeostatic functions and cannot be suppressed

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21
Q

how does a decrese in brain activity affect blood flow?

A

A decrease in brain activity will lead to a decrease in cerebral blood flow. An increase in brain activity will lead to an increase in blood flow.

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22
Q

Name 5 factors that can decrease cerebral blood blow

A

Anesthetic Drugs, temperature, PaCO2, PaO2, cerebral metabolic rate

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23
Q

At what temperature will the bare minimum O2 be consumed by the brain?

A

18C. Temperature can lead to lower oxygen consumption in the 40% of the brain that anesthetic drugs can’t

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24
Q

Which drug increases cerebral metabolic O2 requirements?

A

Ketamine

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25
Q

Does cerebral protection work for global ischemia?

A

NO. It is good for focal ischemia. Examples include corotid endarterectomy, thoracic aneurysm resection, and cerebral aneurysm clipping

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26
Q

What are cardiovascular side effects of thiopental?

A

Decrease SBP (vasodilation) with reflex tachycardia

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27
Q

how does thiopental cause heat loss?

A

Vasodilation

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28
Q

With a low does of thiopental, is laryngospasm possible?

A

yes

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29
Q

Why would you choose benzos over thiopental?

A

Benzos have a more specific action
Thiopental has a lower therapeutic index than benzos
Thiopental use results in tolerance than benzos

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30
Q

Besides how they compare to benzos what are reasons to avoid thiopental?

A 
HANGOVER
High risk for drug interactions
High incidence of abuse
Paradoxical excitement instead of sedation
no skeletal muscle relaxation
Acute intermittent porphyria
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31
Q

What is an absolute contraindication to thiopental?

A

Acute intermittent porphyria

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32
Q

What happens with prolonged infusions of thiopental?

A

Thiopental has a context sensitive half life and may take a long time to wake up when infusions are given over a long time

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33
Q

What is acute intermittent porphyria?

A

Deficiency in the ability to make heme due to a mutation in the porphobilogen deaminase enzyme. barbituates exacerbate this problem

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34
Q

What are the symptoms of porphyria?

A 
abdominal pain
urine retention or dark urine
paresthesia
proximal motor weakness
Increased catecholamine
anxiety, agitation, hysteria
hyponatremia
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35
Q

Can you use benzos with acute intermittent porphyria?

A

Yes

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36
Q

Which is more lipid soluble: methohexital or pentothal?

A

Methohexital

37
Q

What is the IV induction dose of Methohexital? Rectal?

A

1-1.5 mg/kg. 20-30 mg/kg

38
Q

What is a common side effect of methohexital?

A

hiccups

39
Q

what are the components of propofol?

A 
1% propofol
10% soybean oil
2.25% glycerol
1.2% purified egg phosphatide
0.005% disodium edetate (preservative good for 6 hours)
40
Q

Which component of propofol is responsible for bacterial growth? burning?

A

bacterial growth–soybean oil

burning–glycerol

41
Q

how does propofol work?

A

decreases the rate of dissociation of GABA from the GABAa receptor, thereby increasing the duration of the GABA-activated opening of the chloride channels

42
Q

What is the induction dose of Propofol?

A

1-2.5mg/kg IV

43
Q

What is the onset and duration of propofol?

A

onset-30 second with a peak around 90-100 seconds. Duration is 5-10 minutes (dose dependent)

44
Q

What is the distribution half life of propofol?

A

2-8 minutes

45
Q

Where is propofol metabolized?

A

70% liver

30% lungs

46
Q

HOw do renal and liver dysfunction affect the effects of propofol?

A

Doesn’t. propofol wears off due to redistribution

47
Q

Does propofol cross the placenta?

A

Yes, but there are no ill effects on the baby

48
Q

How should you change the dose of propofol for elderly patients?

A

Decrease. the decrease in SVR may be more dramatic

49
Q

What are the effects of propofol on the brain?

A 
decreased CMRO2
Decreased CBF
Decreased ICP
Amnestic
EEG--burst suppression
50
Q

Why do you have to use caution when using propofol for decreased CMRO2 or ICP?

A

Can also decrease MAP leading to a decreased Cerebral perfusion pressure. Oftentimes in this case propofol can be given with norepi

51
Q

What are effects fo propofol on the pulmonary system?

A

RR and Vt,
Bronchodilation
Hypoxic pulmonary vasoconstriction left intact

52
Q

What is hypoxic pulmonary vasoconstriction?

A

Physiologic function where pulmonary arteries constrict in areas of hypoxia, redirecting blood flow to areas of the lungs with higher oxygen concentration. Propofol does not affect this function.

53
Q

What hapatic and renal effects does propofol have?

A

None. may turn urine green if used for long periods of time in ICU

54
Q

What causes allergy in propofol?

A

it is likely due to the propofol molecule itself, not egg

55
Q

Is propofol good for a mapping siezure activitiy?

A

no, may suppress this activity

56
Q

What is an IV sedation dose of propofol?

A

25-100mcg/kg/min

57
Q

What is a GA TIVA dose of propofol?

A

100-200mcg/kg/min

58
Q

Why might you use a low dose of propofol as as an adjunct to a volatile anesthetic?

A

as an anti emetic

59
Q

Why can you only use propofol for 3 days in ICU?

A

Lipids in propofol may lead to hyperlipidemia

60
Q

Why should propofol be avoided in septic patients?

A

these patients already have a low BP and are vasodilated

61
Q

Is etomidate lipid soluble?

A

It is water soluble at an acidic pH, but when you inject it, it becomes lipid soluble in the body

62
Q

T or F. Etomidate is 45% glycerol

A

False. 35%

63
Q

How does etomidate work?

A

GABA activation

Depresses the reticular activating system

64
Q

T or F. Etomidate is a racemic mixture.

A

T

65
Q

What is the onset and duration of Etomidate?

A

Onset 30 second, peak 1 minute

Duration 3-5 minutes

66
Q

How much etomidate is protein bound?

A

75%

67
Q

What is the elimination half time of Etomidate?

A

2.6 hours

68
Q

how is etomidate metabolized and eliminated?

A

Etomidate is mainly metabolized by hydrolysis in the liver to an inactive metabolite.
It is eliminated mostly by the kidneys with a small portion in bile.

69
Q

What effects does etomidate have on the CNS?

A

decreased CBF and CMRO2 (35-45%_
Similar EEG pattern to thiopentol, but with an increase in excitatory spikes on EEG (may decrease seizure threshold), use etomidate with caution in seizure patients

70
Q

What are the CV effects of etomidate?

A

minimal CV response

71
Q

How does etomidate effect ventilation?

A

No decrease in etomidate

72
Q

What are the side effects of etomidate?

A 
Pain
Myoclonus
Adrenocortical suppression--etomidate reversibly inhibits 11-beta hydroxylase, an enzyme in the important for steroid production.  Cortisol levels can be decreased after only 1 dose.  
Hiccups
Increased risk of PONV
73
Q

What are the clinical uses of etomidate?

A

Cardiac challenge
Hypovolemia
Mask ventilation

74
Q

What class of drug is Ketamine?

A

Phencyclidine

75
Q

Where does ketamine work?

A

not on GABA

Works on NMDA, Opioid, MAO and muscarinic receptors

76
Q

What is the onset and duration of ketamine?

A 
Onest: 
IV: anesthetic effect 30 seconds
IM anesthetic effect 3-4 minutes
Duration:
IV: 5-10 minutes
IM: 12-25 minutes
77
Q

What is the solubility and protein binding of ketamine?

A

high lipid solubility, with limited protein binding

78
Q

What is the elimination time of ketamine?

A

2.5 hours by the kidneys

79
Q

How is Ketamine metablolized?

A

by hepatic enzymes.

it has an active metabolite: norketamine–possibly give ketamine analgesic effect?

80
Q

What are subanesthetic infusion rate ketamine?

A

0.1mg/kg/hour up to 0.5mg/kg/hour

81
Q

What kind of pain is ketamine better for?

A

Somatic pain>visceral

82
Q

What is an IV induction dose of ketamine?

A

1-2 mg/kg (30-60 seconds to loss of consciousness)

83
Q

What is IM induction dose of ketamine?

A

4-8 mg/kg

84
Q

How does ketamine affect the CNS?

A

ICP increases
CBF and CMRO2 increased
EEG increased
SSEP ok for monitoring

85
Q

How does Ketamine affect ventilation?

A

NO ventilatory depression
Increased secretions (muscarinic)
decreased bronchomotor tone
Bronchodilator

86
Q

How does ketamine cause its CV effects?

A

Impairs MAO leaving more catecholamines

87
Q

What are the CV effects of ketamine?

A 
Increases blood pressure (systolic>diastolic)
Increases HR
INcreases cardiac output
Myocardial depressant
may cause cardiac rhythm disturbances
88
Q

What are factors that may increase the chance emergence delirium?

A

> 15 yo
girls>guys
prior use
psychiatric disorders

89
Q

What prevents emergence delirium?

A

Benzos

Anesthesia Pharmacology (25 decks)

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