Barbiturates

Question 1

Name the 2 barbiturates:

Answer 1

thiopental

methohexital (Brevital)

Question 2

What drug is used as a substitution of propofol?

Answer 2

Brevital, or methahexidal

Question 3

What is the chief inhibitory neurotransmitter in the vertebrate CNS?

Answer 3

GABA (gamma aminobutyric acid)

Question 4

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?

Answer 4

true

Question 5

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

Answer 5

10.5, makes the drug bacteriostatic

Question 6

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?

Answer 6

true

Question 7

What occurs because of the high pH upon IV injection?

Answer 7

It BURNS!

Question 8

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

Answer 8

propofol

etomidate

Question 9

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

Answer 9

false

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

Question 10

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

Answer 10

hynotic

Question 11

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

Answer 11

seizure, convulsion effects

Question 12

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

Answer 12

True

Question 13

Mechanism of action of thiopental: (2)

Answer 13

decreased dissociation of GABA to GABA_A receptor

increased action/opening of chloride channels

Question 14

Barbiturate pharmacology:

_____ Lipid Solubility

_____Protein Binding

______Uptake

______Redistribution

Answer 14

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

Question 15

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

Answer 15

false

Wake up from redistribution

Question 16

What is the onset time of thiopental?

What is the peak?

What is the duration?

Answer 16

30 sec

1 min

5-8 minutes

Question 17

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

Answer 17

true

Question 18

How is thiopental eliminated? (2)

Answer 18

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.

Question 19

How much of thiopental is bound to proteins?

Answer 19

80%

Question 20

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

Answer 20

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

Question 21

Thiopental metabolism is slow or fast?

Answer 21

slow

redistributes and gives hangover effect due to longer phase of elimination

Question 22

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

Answer 22

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.

Question 23

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

Answer 23

true

It is excreted by the kidneys.

Question 24

Which drug is eliminated faster and why?

Answer 24

methohexital eliminated faster than thiopental

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

Question 25

How are all barbiturates excreted?

Answer 25

by the kidneys

Question 26

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

Answer 26

true

Question 27

What are 3 clinical uses of thiopental?

Answer 27

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.

Question 28

Induction by thiopental pros (2) and con:

Answer 28

rapid onset rapid redistribution hangover, thus longer PACU time

Question 29

What % of cardiac output goes to the brain?

Answer 29

15%

Question 30

Most blood flow goes to ____ matter in the brain for cortical activity. We can decrease the demand of cerebral blood flow by \_\_\_% with thiopental.

Answer 30

gray 60%

Question 31

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

Answer 31

CVP (central venous pressure)

Question 32

Cerebral perfusion pressure, CPP is \_\_\_-\_\_\_\_ mmHg

Answer 32

80-100

Question 33

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

Answer 33

true

Question 34

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

Answer 34

* cerebral metabolic rate * decreased PaCO2 reduces O2 demand * PaO2 * Temperature!!! * anesthetic drugs

Question 35

Minimum PaO2 needed for cerebral blood flow:

Answer 35

60mmHg

Question 36

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

Answer 36

True

Question 37

The colder I am, the lower the metabolism of the brain. Decrease down to \_\_\_\_celcius.

Answer 37

18 degrees

Question 38

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

Answer 38

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

Question 39

CPP (cerebral profusion pressure) equation:

Answer 39

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

Question 40

How is thiopental metabolized?

Answer 40

slowly by liver

Question 41

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

Answer 41

true, contrast to propofol

Question 42

Cerebral venous PO2 is \_\_\_-\_\_\_ mmHg

Answer 42

32-44