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GNURS625 Pharmacology for Anesthesia 1 > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

1
Q

Local Anesthetics are drugs that

A

reversibly block the conduction of electrical impulses along nerve fibers

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2
Q

Removal of the local anesthetic is followed by

A

spontaneous and complete return of nerve conduction, with no evidence of structural damage to nerve fibers.

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3
Q

The ability of the local anesthetic to produce a reversible conduction blockade of impulses along central and peripheral nerve pathways is dependent on:

A

Physiochemicalpropertiesofthelocalanesthetic

Anatomyofthenervebeingblocked

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4
Q

The Myelinated Sheath:

A

insulates the nerve and prevents electrical current from leaking out

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5
Q

The target of local anesthetics is the

A

sodium channel (blocks)

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6
Q

Resting membrane potential of a peripheral nerve is:

A

-70 mV

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7
Q

Voltage Gated Channels:

A

when at -70 mV Sodium moves in, and when at 35 mV Potassium moves out

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8
Q

The Na-K ATPase pump gives

A

energy to transport against the gradient

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9
Q

Resting potential value is

A

-70 mV

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10
Q

Action potential value is

A

35 mV

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11
Q

The mechanism of action of Local Anesthetics is

A

block sodium channels (reversible)

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12
Q

Sodium channel receptors are located

A

on the intracellular side of the cell membrane, and have a greater affinity for the charged form of the local anesthetics

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13
Q

Chemical structures of local anesthetics

A

an unsaturated aromatic ring system
an intermediate carbon group
a tertiary amine

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14
Q

Two types of local anesthetics include

A

Esters

Amides

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15
Q

Esters include

A

Procaine
Chloroprocaine
Tetracaine
Cocaine

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16
Q

AmIdes include

A 
LIdocaine
MepIvacaine
PrIlocaine
BupIvacaine
LevobupIvacaine
RopIvacaine
EtIdocaine
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17
Q

The potency of local anesthetics have a direct correlation with

A

lipid solubility

the more lipid soluble, the more potent

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18
Q

Cm is the

A

minimum concentration of local anesthetic necessary to produce the conduction blockade of nerve impulses

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19
Q

Onset of action of local anesthetics depend on

A

Lipid Solubility- major determinant is amount of LA that is in non ionized form

pKa- pH of the LA at which the amount of non-ionized drug is equal

LA with a pKa closest to physiologic pH will have a higher concentration of non-ionized form that can readily pass through the nerve cell membrane

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20
Q

Once inside the cell, the ionized portion more avidly ….

A

binds the sodium channel inside the cell

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21
Q

Duration of action correlates with

A 
lipid solubility
(highly lipid soluble LA have a longer duration of action, because they are less likely to be cleared by blood flow)

LA that are highly lipid soluble are also typically highly protein bound

22
Q

Sensitivity to blockade is determined by

A

Axonal diameter
(small>large) small more effective

Degree of myelination
(unmyelinated>myelinated) unmyelinated is more sensitive
-hard to get through myelinated sheath

23
Q

In spinal nerves sensitivity to local anesthetics is

A

autonomic>sensory>motor

auto is more affected than sensory, sensory is more affected than motor

24
Q

Nerve fibers are classified into 3 groups:

A

A, B, C

25
Q

A-fibers are the _______ nerve fibers, so the they are the _______ sensitive

A

largest axonal nerve fibers

least sensive

26
Q

B- fibers are the ________ nerve fibers

A

intermediate

more sensitive than A, less sensitive than C

27
Q

C fibers are the ______ nerve fibers, they are _______

A

smallest

unmyelinated

28
Q

Unlike other medications, local anesthetics are meant to

A

remain in the area of injection or application

29
Q

The higher the concentration of drug injected that remain in the area of the nerves to be blocked, the ______ the onset of action

A

faster

30
Q

Systemic absorption of injected LA depends on:

A

Blood Flow

  • site of injection
  • presence of vasoconstrictors
  • specific local anesthetic agent
31
Q

The addition of _______ to an LA, will prolong the duration of the anesthetic

A

epinephrine

32
Q

All local anesthetics except _________, produce relaxation of vascular smooth muscle

A

cocaine= vasoconstrictor, used for ENT surgeries

33
Q

Esters are predominantly metabolized by

A

pseudocholinesterase

34
Q

Procaine and benzocaine (esters) are broken down into

A

PABA (associated with allergic reactions)

35
Q

Patients with genetically abnormal pseudocholinesterase are at risk for

A

toxic side effects

36
Q

Amides are metabolized by

A

microsomal P-450 enzymes in the liver

37
Q

Amide metabolism is ______ than ester hydrolysis

A

slower

38
Q

Decrease in liver function will reduce metabolism of ________ and increase toxicity

A

amides

39
Q

Metabolites of prilocaine accumulate after large doses and convert Hgb to ________

A

methemoglobin (tx is methylene blue)

40
Q

Methemoglobinemia S/S include

A

brownish gray cyanosis
tachypnea
metabolic acidosis
severe S/S ensue with: tissue hypoxia, headache, irritability, loss of consciousness

immediate reversal with methylene blue

41
Q

The peak plasma concentration is dependent upon the __________ rather than the volume or concentration

A

total dose of local anesthetic

42
Q

Additives to local anesthetic include

A

Opioids
Sodium Bicarbonate
Epinephrine
-these are added to increase the safety, quality, intensity, duration, and rate of onset of anesthetic

43
Q

Ion trapping results from changes in

A

pH in relationship to the agents pKa

44
Q

The more acidic the tissue (sepsis, infection = acidosis) the more

A

ion trapping (stuck in cell= longer duration of action) sticks around longer ( a base going into an acid)

45
Q

Systemic toxicity of local anesthetics can occur from

A

inadvertent intravascular injection

administration of excessive dose

46
Q

toxicity of LA include _____ and _____ side effects

A

cardiovascular and CNS
HTN/Tachy- brad/hypo - asystole
psychically abnormal - confusion - seizure

47
Q

Esters / Amides have a higher rate of allergic reactions

A

esters

48
Q

Topical cocaine has _________ properties

A

vasoconstrictor

49
Q

Epinephrine should not be injected around end arteries such as

A

fingers/ toes
ears/ nose
genitals

50
Q

Disadvantages of local infiltration anesthesia

A

large amount of local anesthetic must be used to block relatively small areas
pain on injection
-rate of injection
-alkalization of local (buffering)

GNURS625 Pharmacology for Anesthesia 1 (5 decks)

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