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Anes. Pharm. Me > Barbiturates > Flashcards

Barbiturates Flashcards

1
Q

Name the 2 barbiturates:

A

thiopental

methohexital (Brevital)

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2
Q

What drug is used as a substitution of propofol?

A

Brevital, or methahexidal

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3
Q

What is the chief inhibitory neurotransmitter in the vertebrate CNS?

A

GABA (gamma aminobutyric acid)

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4
Q

Barbiturates most likely produce their sedative hypnotic effects through an interaction with the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) in the CNS. True or false?

A

true

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5
Q

What is the pH of thiopental and why is this significant?

A

10.5, makes the drug bacteriostatic

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6
Q

The ability of barbiturates to uniquely depress the reticular activating system, which is presumed to be important in the maintenance of wakefulness may reflect the ability of barbiturates to decrease the rate of dissociation of GABA from its receptors. True or false?

A

true

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7
Q

What occurs because of the high pH upon IV injection?

A

It BURNS!

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8
Q

Methohexital (Brevital) is very similar to mechanism of what 2 drugs:

A

propofol

etomidate

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9
Q

Thiopental is compatible with our opioids, catecholamines, and NMBs that are acidic. True or false?

A

false

crystallizes in the line, but some commercial preparations contain sodium carbonate to prevent this

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10
Q

The manipulation of C2 atom on thiopental increases what effects of the drug?

A

hynotic

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11
Q

The manipulation of C5 of thiopental enhances what effects of the drug?

A

seizure, convulsion effects

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12
Q

Barbiturates produce their pharmacological effects by increasing the duration of chloride ion channel opening at the GABAA receptor (pharmacodynamics: this increases the efficacy of GABA). True or false?

A

True

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13
Q

Mechanism of action of thiopental: (2)

A

decreased dissociation of GABA to GABAA receptor

increased action/opening of chloride channels

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14
Q

Barbiturate pharmacology:

_____ Lipid Solubility

_____Protein Binding

______Uptake

______Redistribution

A

high lipid solubility

high protein binding via albumin

quick uptake about 30 sec in brain, like propofol

high distribution, wake up from redistribution like propofol, NOT METABOLISM

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15
Q

Pts wake up from thiopental by metabolism of the drug. True or false?

A

false

Wake up from redistribution

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16
Q

What is the onset time of thiopental?

What is the peak?

What is the duration?

A

30 sec

1 min

5-8 minutes

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17
Q

Hypovolemia may decrease blood flow to skeletal muscles whereas blood flow to the brain and heart are maintained. True or false?

A

true

18
Q

How is thiopental eliminated? (2)

A

metabolism and excretion

Two-compartment model demonstrates the distribution phase (1st phase) and the elimination phase (2nd phase).

During the distribution phase, the drug moves from the central compartment to the peripheral compartment.

19
Q

How much of thiopental is bound to proteins?

A

80%

20
Q

If pt has hypoalbemia, will thiopental be more or less effective?

A

more, because more free drug available because less is bound to proteins

21
Q

Thiopental metabolism is slow or fast?

A

slow

redistributes and gives hangover effect due to longer phase of elimination

22
Q

Blood acidosis will _____ and alkalosis will ______ the intensity of thiopental.

A

increase

decrease

The nonionized form of drug has greater access to the CNS because of its high lipid solubility.The pk of thiopental is near 7.6.

23
Q

There is an active metabolite in thiopental. True or false.

A

true

It is excreted by the kidneys.

24
Q

Which drug is eliminated faster and why?

A

methohexital eliminated faster than thiopental

lesser lipid solubility thus more methohexital remains in the plasma to become available for metabolism

25
Q

How are all barbiturates excreted?

A

by the kidneys

26
Q

High degree of protein binding limits the magnitude of filtration, whereas high lipid solubility favors reabsorption. True or false?

A

true

27
Q

What are 3 clinical uses of thiopental?

A

induction of anesthesia

treatment of increased ICP

cerebral protection: barbiturates decreases cerebral metabolic O2 requirements which may provide protection to the brain, but not good for global ischemia.

28
Q

Induction by thiopental pros (2) and con:

A

rapid onset

rapid redistribution

hangover, thus longer PACU time

29
Q

What % of cardiac output goes to the brain?

A

15%

30
Q

Most blood flow goes to ____ matter in the brain for cortical activity.

We can decrease the demand of cerebral blood flow by ___% with thiopental.

A

gray

60%

31
Q

If we don’t have ICP values we can use ____ pressure values.

A

CVP (central venous pressure)

32
Q

Cerebral perfusion pressure, CPP is ___-____ mmHg

A

80-100

33
Q

Suppression of cerebral metabolism leads to a reduction in blood flow. True or false?

A

true

34
Q

Chemical regulation of cerebral blood flow can be affected by: (5)

A
  • cerebral metabolic rate
  • decreased PaCO2 reduces O2 demand
  • PaO2
  • Temperature!!!
  • anesthetic drugs
35
Q

Minimum PaO2 needed for cerebral blood flow:

A

60mmHg

36
Q

We can get down to 0 electrical activity safely with anesthetic drugs. True or false?

A

True

37
Q

The colder I am, the lower the metabolism of the brain. Decrease down to ____celcius.

A

18 degrees

38
Q

What do we need to be careful of during ICP therapy?

A

Use caution when decreasing the cerebral blood flow with agents like propofol and benzos because we can also decrease cerebral perfusion pressure.

39
Q

CPP (cerebral profusion pressure) equation:

A

MAP - ICP

If no ICP, CVP can be used instead 8-12mmHg

40
Q

How is thiopental metabolized?

A

slowly by liver

41
Q

Liver dysfunction will slow metabolism of thiopental. True or false?

A

true, contrast to propofol

42
Q

Cerebral venous PO2 is ___-___ mmHg

A

32-44

Anes. Pharm. Me (15 decks)

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