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GNURS625 Pharmacology for Anesthesia 1 > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

(50 cards)

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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

Study These Flashcards
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

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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

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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:

25
A-fibers are the _______ nerve fibers, so the they are the _______ sensitive
largest axonal nerve fibers | least sensive
26
B- fibers are the ________ nerve fibers
intermediate | more sensitive than A, less sensitive than C
27
C fibers are the ______ nerve fibers, they are _______
smallest | unmyelinated
28
Unlike other medications, local anesthetics are meant to
remain in the area of injection or application
29
The higher the concentration of drug injected that remain in the area of the nerves to be blocked, the ______ the onset of action
faster
30
Systemic absorption of injected LA depends on:
Blood Flow - site of injection - presence of vasoconstrictors - specific local anesthetic agent
31
The addition of _______ to an LA, will prolong the duration of the anesthetic
epinephrine
32
All local anesthetics except _________, produce relaxation of vascular smooth muscle
cocaine= vasoconstrictor, used for ENT surgeries
33
Esters are predominantly metabolized by
pseudocholinesterase
34
Procaine and benzocaine (esters) are broken down into
PABA (associated with allergic reactions)
35
Patients with genetically abnormal pseudocholinesterase are at risk for
toxic side effects
36
Amides are metabolized by
microsomal P-450 enzymes in the liver
37
Amide metabolism is ______ than ester hydrolysis
slower
38
Decrease in liver function will reduce metabolism of ________ and increase toxicity
amides
39
Metabolites of prilocaine accumulate after large doses and convert Hgb to ________
methemoglobin (tx is methylene blue)
40
Methemoglobinemia S/S include
brownish gray cyanosis tachypnea metabolic acidosis severe S/S ensue with: tissue hypoxia, headache, irritability, loss of consciousness immediate reversal with methylene blue
41
The peak plasma concentration is dependent upon the __________ rather than the volume or concentration
total dose of local anesthetic
42
Additives to local anesthetic include
Opioids Sodium Bicarbonate Epinephrine -these are added to increase the safety, quality, intensity, duration, and rate of onset of anesthetic
43
Ion trapping results from changes in
pH in relationship to the agents pKa
44
The more acidic the tissue (sepsis, infection = acidosis) the more
ion trapping (stuck in cell= longer duration of action) sticks around longer ( a base going into an acid)
45
Systemic toxicity of local anesthetics can occur from
inadvertent intravascular injection | administration of excessive dose
46
toxicity of LA include _____ and _____ side effects
cardiovascular and CNS HTN/Tachy- brad/hypo - asystole psychically abnormal - confusion - seizure
47
Esters / Amides have a higher rate of allergic reactions
esters
48
Topical cocaine has _________ properties
vasoconstrictor
49
Epinephrine should not be injected around end arteries such as
fingers/ toes ears/ nose genitals
50
Disadvantages of local infiltration anesthesia
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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