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Pharmacology 680 > Pentothal/Brevital/Etom/Dex > Flashcards

Pentothal/Brevital/Etom/Dex Flashcards

1
Q

Intravenous Anesthetic Agent moa

A

It changes the level of consciousness (fast) by
depressing the reticular activating system
either by enhancing the inhibition
properties of GABA or inhibiting the NMDA
excitatory synapses.

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2
Q

What can be used as a TIVA when volatiles contraindicated?

A

IV anesthetic drugs

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3
Q

List 6 IV anesthetic agents that are APPROVED for GA

A
  1. propofol
  2. ketamine
  3. thiopental - pentathol
  4. methohexital
  5. etomidate
  6. benzos
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4
Q

What med is NOT approved for GA?

A

dextmetodine

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5
Q

Vessel-rich (brain, heart, liver, kidney,

endocrine) receives what % CO

A

75%

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6
Q

Lean muscle (muscle, skin) receives what % CO

A

19%

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7
Q

Fat receives what %

A

6%

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8
Q

vessel -poor (bone, ligament, cartilage)

A

0%

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9
Q

What is the primary mechanism for terminating central effects of IV induction agents?

A

redistribution from central compartment (brain) to the peripheral compartment (plasma/muscle)

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10
Q

describe the Redistribution – (alpha phase)

A

the plasma concentration of the drug has
declined to the point that the drug moves
out of the vessel-rich central group and is
then taken into the peripheral group
[termination of effect]

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11
Q

what is the Elimination – (beta phase)

A

involves metabolism and excretion

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12
Q

how long does it take for thiopental to reach equilibrium with skeletal muscles?

A

15 minutes

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13
Q

why do large or repeated doses of barbiturates produce a cumulative effect?

A

storage capacity of fat

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14
Q

What 4 things would make the ideal IV anesthetic (think effects)?

A

anticonvulsant
antiemetic
analgesic
amnestic

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15
Q

What is the only agent you can give ALONE as an anesthetic?

A

ketamine

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16
Q

Barbiturate – thiobarbiturate (sulfur)

A

Thiopental (Sodium

Pentothal)

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17
Q

what state accounts for bacteriostasis of pentothal?

A

alkaline - 2.5% sodium salt preparation is water-
soluble, but highly alkaline with a pH of
10.5

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18
Q

how long does pentathol last when reconstituted from powder form?

A

6 days at room temperature, 2 weeks

in refrig

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19
Q

what happens to pentathol if mixed with opioids,
catecholamines, and NMB, which are
more acidic in IV line?

A

significant precipitate forms. clear the line after giving

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20
Q

Is there pain upon injection of thipental?

A

no, unlike prop

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21
Q

MOA thiopental

A

Increases the duration of GABA activating its receptor
causing the chloride ion channels to remain open
longer, allowing increased influx, and causing the cell
membrane to be hyperpolarized and thus inhibited

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22
Q

thiopental Mimics GABA at its receptor to directly cause

A

chloride channels to open

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23
Q

what other receptors are activated with thiopen admin?

A

glutamate
adenosine
nACh

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24
Q

important concept to remember about GABA receptor?

A

multiple things can bind to it same time, so can have big synergism.
[ex: you give midazolam preop, wont have to give as much pentathol to induce]

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25
Q

cardiovascular effects of thiopental are overall…

A

minimal, compared to prop

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26
Q

Cards effect thiopental

A

transient decrease BP [rate of admin doesnt prevent]
increase HR
peripheral vasodilation

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27
Q

vasodilation of cutaneous and skeletal muscle blood vessels with admin thiopent can cause

A

heat loss and reduction in temp

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28
Q

what pt can thiopent be good for and why?

A

cards r/t arterial vasodilation

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29
Q

does thiopen cause histamine release?

A

yes and you will see greater drop in BP

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30
Q

thiopent Decreases the sensitivity of what to CO2?

A

medullary ventilatory center

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31
Q

how do respirations return with thiopent?

A

small TV and slow RR

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32
Q

what is interesting about resp reflexes with thiopent?

A

Reflexes remain intact with apnea, allowing

possibility of laryngospasm

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33
Q

what drug is recommended for insertion of LMA?

A

prop

34
Q

how does thiopen effect CNS?

A

Decreases ICP by decreasing cerebral blood

volume and CMRO2 by 55% [best for cerebral protection]

35
Q

explain what it means that demand

is less than supply in referring to cerebral protection with thiopen

A

The induced reduction in the cerebral
metabolic oxygen requirement is greater than
the decrease in cerebral blood flow

36
Q

what types of cases are cerebral protection shown to be successful with pent?

A

Incomplete cerebral ischemia cases protection is successful. (CBP, hypotension,circ. arrest)
Global cerebral ischemia cases show no
protection. (cardiac arrest)

37
Q

what does a dose 39.6 mg/kg of thiopent cause?

A

more use of inotropes due to a trash BP, found that hypothermia added same cerebral protection without problems

38
Q

what weird syndrome can be exacerbated with thiop?

A

acute intermittent porphyria r/t the stimulation and increase in production of heme

39
Q

can thiopen cross placenta?

A

yes, but 4 mg/kg is safe to give

40
Q

what % is thiopen protein bound and what does that mean?

A

85% - only unbound drug is available to cross BBB and have effect, the more drug bound, the slower the diffusion rate of the drug
[lower dose in ppl low proteins]

41
Q

what two patients do you decrease dose of thiopent?

A 
elderly
early pregnancy (7-13 weeks)
42
Q

Barbiturate – oxybarbiturate – less lipid

soluble than thiopental

A

Methohexital (Brevital)

43
Q

how long does methohex last once reconstituted?

A

6 weeks in refrig, unlike thio that lasts 2 weeks

44
Q

MOA methohex

A

Increases the duration of GABA activating its receptor
causing the chloride ion channels to remain open
longer, allowing increased influx, and causing the cell
membrane to be hyperpolarized and thus inhibited

45
Q

pethathol gives patients what type of effect after waking

A

hangover

46
Q

compare metabolism of methohex and thiopen

A

Metabolism of methohexital occurs three
to four times faster than that of thiopental
due to the decreased lipid solubility,
which allows more methohexital to stay in
the plasma

47
Q

the metabolism of methohex causes:

A

less hangover, rapid awakening, less accumulation

48
Q

Disadvantage Methohexital

A

more excitatory activity –

myoclonus, hiccoughs (dd)

49
Q

how to decrease excitatory activity of methohex?

A

opioids preop and dose of 1.0-1.5 mg/kg of methohexital

do NOT INFUSE - seizures

50
Q

potency of methohex vs pentathol and why

A 
More potent (2.5X) than thiopental due to 
higher % nonionized at blood pH of 7.4
51
Q

does methohex cause histamine release?

A

no, thiopen does

52
Q

CV effects methohex

A

similar to thiopental with
equivalent doses or maybe less
hypotension due to increase in HR is
better preserved

53
Q

Chemically unrelated to any other IV anesthetic

A

Etomidate

54
Q

etomidate contains a Carboxylated imidazole-containing compound which means

A

water-soluble at an acidic pH and lipid

soluble at physiologic pH

55
Q

moa etomidate

A

mimics the inhibitory effects of
GABA by increasing the receptors affinity
to GABA; thus depresses the reticular
activating system

56
Q

Unlike thiopental, etomidate has excitatory

activity to cause myoclonus in

A

30-60% of pts.

Myoclonus – 50-80% who don’t receive premedication ((fentanyl or benzo or sm dose of etomidate)

57
Q

how does etomidate cause mycolonus?

A

disinhibition of subcortical structures that normally suppress extrapyramidal motor activity

58
Q

Cardiovascular effects etomidate

A

[better than others]
15% decrease in MAP
minimal changes HR, SV, CO
decrease in svr

59
Q

what patient is etomidate good for?

A

pts with poor left ventricle

60
Q

Respiratory effects etomidate?

A

decreased TV, increased RR

less effect than barbs

61
Q

when is etomidate advantageous

A

when spontaneous ventilation

is desired; apnea doesn’t always occur (however will become apneic when combined volatiles/opioids)

62
Q

etomidate cns effects Similar to thiopental, but with a decrease of CMRO2 of

A

35-45%

63
Q

who should you avoid etomidate with?

A

seizure patients

64
Q

explain Adrenocortical suppression with etomidate

A

Causes an inhibition of the conversion of
cholesterol to cortisol (Inhibition of the
enzyme which performs 11-beta- enzyme reaction)
[decreased cortisol and aldosterone]

65
Q

how long does adrenocortical supporession last with etomidate?

A

4-8 hours, up to 48 hrs

66
Q

why is adrenocortical suppression significant with etom

A

Septic and bleeding patients need to have

appropriate stress response.

67
Q

what enzyme is inhibited by etomidate

A

11-beta-hydroxylase

68
Q

Metabolism etom compared to thiopen

A

by hepatic microsomal
enzymes and plasma esterases produces
clearance 5 times faster than thiopental

69
Q

Alpha2-adrenergic agonist

A

Dexmedetomidine

Precedex

70
Q

MOA dext

A

Hyperpolarization with efflux of K+
Reduced NE release due to presynaptic receptors
Decrease cAMP concentration by inhibiting adenylyl cyclase

71
Q

what is key element of moa from anesth standpoint of dex?

A

neuronal hyperpolarization

72
Q

dex causes Hypertension – r/t loading dose (don’t bolus) r/t

A

May have direct effect on alpha2B and

alpha2A receptors

73
Q

Factors increasing risk of hypotension with dext?

A

High sympathetic tone

Diabetic, elderly, hypovolemic

74
Q

Sedation and analgesia with little

depression of ventilation

A

Dexmedetomidine (Precedex)

75
Q

whats cool about dext?

A

you can wean vent without titration, easily arousable

76
Q

Dexmedetomidine (Precedex) Decreases MAC by

A

> 90%

77
Q

Dexmedetomidine (Precedex) Approved for

A

infusions of 24 hours and

sedation cases

78
Q

Alternative to ketamine for awake

fiberoptic intubations?

A

dext r/t antisialogue effects

79
Q

dose of dext that decreased propofol infusion

and analgesia requirement

A

0.5 mcg/kg IV

80
Q

how does dext Reduces shivering

A

inhibits central thermoregulatory control,
vasoconstriction – more susceptible to
hypothermia

81
Q

Emergence delirium prophylaxis

A

dext

82
Q

used as sedation
during surgery with subarachnoid block is
the main anesthetic and why

A

IV dexmedetomidine
No significant respiratory depression
Dependable, titratable intraoperative sedation
Wide safety margin

Pharmacology 680 (19 decks)

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