Local Anesthetics Flashcards

1
Q

Benzocaine

Procaine

A

Cat: Short acting ester LA (benzocaine = topical, procaine = infiltrate, epidural)
MOA: Blocks activated/inactivated Na channels
Adverse: allergy to PABA, anxiety, convulsions (GABA block - tx w/diazepam), CV collapse

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2
Q

Cocaine

A

Cat: short acting ester for nose/throat
MOA: block activated/inactivated Na channels, use dependent
SE: PABA allergy, anxiety, convulsions (GABA block - tx w/ diazepam), inc HR/contraction, VFib, hypertension
Beware of drug abuse

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3
Q

Lidocaine

Ropivacaine

A

Cat: long acting amide LA
MOA: block activated and inactivated Na channels, use dependent
SE: anxiety, convulsions d/t GABA, CV collapse (bradycardia, hypotension)

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4
Q

Which LA has reduced affinity for cardiac sodium channels and is therefore associated with less cardiac toxicity?

A

S-isomer of ropivacaine

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5
Q

Locations of use of lidocaine vs ropivacaine

A

Lidocaine: infiltration, Bier block, peripheral, epidural, spinal
Ropivacaine: peripheral

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6
Q

Epinephrine

A

Reduces systemic absorp of local anesthetics via vasoconstriction via alpha 1 adrenergic activation
SE: localized tissue necrosis
Increases LA action by 50%

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7
Q

Clonidine

A

Used with LAs for epidural and spinal admin to further reduce pain transmission
MOA: prevents NT release at C and Ad fibers via presynaptic alpha 2

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8
Q

Diazepam

A

Treat convulsions d/t systemic absorption of LA into CNS by activating GABA receptors in CNS

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9
Q

3 characteristics that determine level of lipophilic

A
  1. # of hydrocarbon chains and length
  2. Length of intermediate connecting chain
  3. # /length of aromatic ring hydrocarbons
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10
Q

A delta fibers

A

Fast pain
Glutamate to NMDA
Neospinthalmic neurons
Myelinated

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11
Q

C fibers

A

Second pain
Substance P to P receptors
Paleospinothalmic neurons

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12
Q

Esters

A

One “i”
Short duration of action
Metab by plasma/live pseudocholinesterases
Allergies: PABA derivatives

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13
Q

Amides

A

Two Is
Longer duration of action
Metab: liver p450

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14
Q

Why don’t local anesthetics work well in infected tissue?

A

Lower pH means that the LA is more charged, leaving it unable to cross the cell membrane leading to decreased potency and longer onset time

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15
Q

Fiber types most susceptible to LA

A

Small diameter
Myelinated
Firing a lot
Exterior fibers

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16
Q

Topical anesthesia

A

ENT procedures - directly to surface

Ex. Benzocaine or cocaine

17
Q

Infiltration anesthesia

A

Injection into skin, subcut, or mucous membrane

Ex. Procaine or lidocaine

18
Q

Bier block

A

Regional anesthesia via injection and impeding of venous flow with a tourniquet < 1 hr
Ex. Lidocaine

19
Q

Peripheral nerve block

A

Around nerve or plexus for regional anesthesia

Ex. Lidocaine or ropivacaine

20
Q

Epidural and spinal anesthesia

A

Epidural doesn’t puncture dura
Spinal does puncture dura
Procaine and lidocaine

21
Q

Greatest risk for system toxicity

A

Areas of high vascularization
Intercostal > caudal > epidural

Low: brachial plexus, sciatic nerve

22
Q

Low systemic absorption of LA effects

A

Disruption of sensory perception

23
Q

High systemic absorption of LA effects

A

Brain: confusion, tremor, convulsions
CV: dec contractility, bradycardia, vasodilation, hypotension

24
Q

Direct injection of LA into vasculature causes…

A
Temporary blindness
Aphasia
Hemiparesis
Convulsions
Coma
Cardiac arrest
25
Q

What can help reduce cardiac and neurotoxicities from direct injection

A

IV lipid emulsions