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NS2 Test 3 > Local Anesthetics DSA > Flashcards

Local Anesthetics DSA Flashcards

1
Q

Local anesthetics

A
  • benzocaine
  • bupivacaine
  • cocaine
  • dibucaine
  • lidocaine
  • procaine
  • BBCDLP
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2
Q

local anesthetics chemistry

A
  • contain hydrophilic (amine) and hydrophobic (aromatic ring)
  • separated by ester or amide linkage
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3
Q

ester linkage duration of action

A

(procaine)

-more prone to hydrolysis than those with amide links (lidocaine) so have shorter duration of action

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4
Q

use of vasoconstrictor substances with local anesthetics

A
  • reduces systemic absorption of agents

- useful for drugs with intermediate or short durations of action

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5
Q

cocaine–unique?

A

-intrinsic sympathomimetic vasoconstricive properties (inhibits reuptake of NE)

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6
Q

ester-type agents–metabolism

A
  • metabolized in plasma

- hydrolyzed by circulating butyrlcholinesterase (plasma cholinesterase)

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7
Q

amide-type agents–metabolism

A
  • hydrolyzed by liver CYP450

- toxicity can occur in patients with hepatic disease

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8
Q

Local anesthetics MOA

A

-bind reversibly to Na channels in nerves–stop spread of APs across nerve axons

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9
Q

local anestehtics–more potent when? examples?

A
  • smaller and more lipophilic= faster rate of interaction with Na channel=more potent
  • tetracaine, bupivacaine, ropivacaine (TBR)
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10
Q

local anesthetics preferentially block what fibers?

A
  • small fibers
  • myelinated nerves
  • preganglionic B fibers blocked before smaller unmyelinated C fibers)
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11
Q

Local anesthetics preferentially block what fibers–firing frequency

A

-fibers that fire at higher frequencies of depolarization

Type A delta and C fibers–blocked earlier than large A alpha fibers

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12
Q

in bundles of large mixed nerves, what is blocked first?

A

-motor neurons before sensory because motor nerves are usually located circumferentially

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13
Q

in extremities, what is blocked?

A
  • proximal sensory fibers are in the outer portion of nerve trunk
  • distal sensory innervation is located in core of nerve
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14
Q

Type A fibers–diameter, myelination, sensitivity to block

A
  • alpha (prop, motor)-12-20, heavy, +
  • beta (touch, pressure)-5-12, heavy, ++
  • gamma (m spindles)- 3-6, heavy, ++
  • delta (pain, T)-2-5, heavy, +++
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15
Q

Type B fibers–diameter, myelination, sensitivity to block

Type C fibers–diameter, myelination, sensitivity to block

A

(preganglionic autonomic)

-

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16
Q

infiltration anesthesia

A
  • directly into tissue in vicinity of peripheral nerve

- can be superficial enough to only include skin and deep enough to include intraabdominal organs

17
Q

block anesthesia–into? purpose?

A
  • into major n trunks
  • anestheize a region distal to the site of injection
  • (femoral nerve block for surgery distal to knee)
  • brachial plexus block–UE or shoulders
18
Q

spinal anesthesia

A
  • into CSF in lumbar space

- anesthesia over a considerable fraction of body

19
Q

epidural anesthesia

A
  • into epidural space

- in sacral hiatus, or in lumbar, thoracic, or cervical regions of spine

20
Q

IV regional anesthesia (Bier block)–used for?

A

-used for short surgical produces (

21
Q

epinephrine–containing solutions–shouldnt be injected into?

A
  • tissues supplied by end arteries (fingers, toe, ears, nose, penis) because vasoconstriction may cause gangrene
  • careful when into muscle tissue–can activate B2 receptors–dilation–increase potential for systemic toxicity
22
Q

local anesthetics–2 forms of local anesthetic toxicity

A
  • systemic effects following absorption of local anesthetics

- direct neurotoxicity from local effects of these drugs when given close to spinal cord and other major nerve trunks

23
Q

local anesthetics–effects on CNS–low concentration and high concentration

A
  • low concentration–sleepiness, light headedness, visual/auditory disturbances, restlessness
  • high concentration–nystagmus, muscle twitching, convulsions
  • when large doses required–premedication with parenteral benzodiazepine (diazepam or midozolam) can provid prophylaxis against CNS toxicity by raising seizure threshold (local anesthetics cause depression of cortical inhibitory pathways)
  • central stimulation followed by depression
24
Q

local anesthetics–effects on CV system

A
  • block Na channels, decrease electrical excitability, conduction rate, force of contraction, and arteriolar dilation–leads to systemic hypotension
  • bupivacaine–most cardiotoxic (long durations of action)
25
Q

cocaine–effects on CV system

A

-inhibits NE reuptake–results in vasoconstriction–hypertension, cardiac arrhythmias

26
Q

lidocaine–class 1b antiarrythmic

A
  • suppresses automaticity of conduction tissue–increases electrical stimulation threshold of ventricle
  • blocks initiation and conduction of nerve impulses–inhibition of depolarization–blockade of conduction
27
Q

Lidocaine–most common adverse effect

A
  • CNS toxicity

- mild, dose-dependent, resolves upon discontinuation

28
Q

allergic reactions that are most common

A
  • ester-type local anesthetics

- ester type only have 1 i, while amide types have at least 2 i’s in drug name

29
Q

benzocaine–used for

A
  • used only as topical agent

- dermatologic conditions, hemorrhoids, premature ejaculation, anesthetic lubricant

30
Q

bupivacaine–used for

A
  • long duration of action–most cardiotoxic

- tendency to provide more sensory than motor

31
Q

cocaine–used for

A
  • blockade on nerve impulses and local vasoconstriction actions (inhibits NE reuptake)
  • euphoric properties–due to inhibition of catecholamine reuptake
  • used as topical anesthetic of upper respiratory tract
32
Q

dibucaine–used for

A

–toxicity associated with injections so only used as topical cream on skin

33
Q

lidocaine used for

A
  • protypical amide local anesthetic!!
  • alternative choice for individuals sensitive to ester type local anesthetics
  • faster, more intense, longer lasting anesthesia than procaine
  • used as antiarrhthmic agent
  • medium duration of action
34
Q

procaine used for

A
  • lower potency, slower onset, shorter duration of action (than newer agents)
  • used for infiltration anesthesia (injection into area of terminal nerve endings)
  • metabolized to para-aminobenzoic acid–inhibits action of sulfonamide antibiotics
  • short duration of action
35
Q

medium duration of action

A
  • lidocaine

- cocaine

36
Q

long duration of action

A
  • bupivacaine

- tetracaine

37
Q

short duration of action

A

-procaine

NS2 Test 3 (14 decks)

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