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Neurology 2 > Local Anesthetics - Kruse > Flashcards

Local Anesthetics - Kruse Flashcards

1
Q

Function of local anesthetics

A

Bind and block VGSC’s w/in nerves, blocking action potential potentiation

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2
Q

2 classes of local anesthetics (w/ members)

A

Amides - Lidocaine, Mepivacaine, Bupivacaine, Ropivacaine, Articaine

Esters - Benzocaine, Cocaine, Procaine, Tetracaine

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3
Q

How to remember which ones are amides (vs. esters)?

A 
Amides = have 2 "i"s in the name
Esters = have 1 "i" in the name
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4
Q

Duration of action of amides vs. esters

A

Esters - more prone to hydrolysis = shorter duration of action

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5
Q

What may be indicated to be used with the shorter duration drugs (esters)?

A

Vasoconstrictors (epinephrine) - to reduce systemic absorption and destruction (alpha-1 agonist)

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6
Q

How is cocaine unique?

A

Intrinsic sympathomimetic vasoconstrictive properties (only ester that does NOT need epinephrine)

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7
Q

Metabolism of esters vs. amides

A

Esters - PLASMA butyrylcholinesterase

Amides - LIVER P450 enzymes

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8
Q

Potential contraindication to using amides

A

Hepatic disease - can accumulate amide drug metabolites and cause toxicity

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9
Q

Potency of local anesthetics

A

More lipophilic = more potent = longer duration of action

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10
Q

Which are the more lipophilic ones?

So?

A

Tetracaine, Bupivacaine, Ropivacaine

More potent and longer duration of action

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11
Q

Which nerve fibers are blocked more often by local anesthetics?

A

Smaller, more myelinated fibers
Motor before sensory (motor = more peripheral)
Proximal sensory before distal sensory (extremities)

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12
Q

Rank nerve fibers in order from MOST to LEAST affected by local anesthetics (6 total)

A
  1. B - small, myelinated
  2. C - small, unmyelinated
  3. A-delta
  4. A-gamma
  5. A-beta
  6. A-alpha
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13
Q

3 major routes of administration

A
  1. Topical
  2. Injections
  3. IV regional
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14
Q

Infiltration anesthesia

A

Injection directly into vicinity of peripheral nerve endings

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15
Q

Block anesthesia

Examples?

A

Injection directly into major nerve trunk (anesthetize region distal to site of injection)

Femoral nerve (distal to knee surgery), brachial plexus (UE or shoulder surgery)

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16
Q

Spinal anesthesia

A

Injection into CSF in lumbar space (anesthetize portion of body below the level)

17
Q

Epidural anesthesia

A

Injection or continuous infusion into epidural space (all regions of spinal cord)

18
Q

IV regional anesthesia

A

Short procedures (

19
Q

While epinephrine (alpha-1 agonists) may be used as a vasoconstrictor along w/ a local anesthetic to prolong the life of the drug, where should the epinephrine NOT be placed?

Where should it be placed WITH CAUTION?

A

Tissues supplied by end arteries (fingers, toes, ears, nose, penis)

Vasoconstriction could cause GANGRENE

Muscle tissues (Beta-2 agonist in muscle vasculature could cause vasodilation and systemic toxicity)

20
Q

Which local anesthetic does NOT need epinephrine?

A

Cocaine - potent vasoconstrictor (sympathomimetic)

21
Q

2 types of undesired effects from local anesthetic toxicity

A
  1. Systemic (CV or CNS depression)

2. Direct neurotoxicity (when given near major nerve trunks or spinal cord)

22
Q

A patient needs a large amount of a local anesthetic. What is indicated for protective measures?

A

A parenteral benzodiazepine (Diazepam or Midazolam) - to provide prophylaxis against CNS toxicity by raising seizure threshold

23
Q

Why might you need a benzo along with a local anesthetic?

A

Systemic anesthetic –> depression of cortical inhibitory pathways –> unopposed activity of excitatory pathways (seizure)

24
Q

Side effects of local anesthetics on CV system

A

Decreased heart conduction –> hypotension

Cocaine –> hypertension, arrhythmias, ischemia (via vasoconstriction)

25
Q

In addition to being an anesthetic, Lidocaine can be used as a _____

A

Anti-arrhythmic (slow down heart, let it re-set)

26
Q

If a patient is allergic to an ester type, what should you do?

A

Try an amide type (most likely allergic to other ester types)

27
Q

Benzocaine

A

Topical ONLY + anesthetic lubricant for tubes

28
Q

Bupivacaine

A

Long duration –> prolonged anesthesia

SENSORY over MOTOR

29
Q

Cocaine

A

Inhibition of catecholamine reuptake –> euphoria

Topical in upper respiratory tract

30
Q

Dibucaine

A

SKIN TOPICAL ONLY

31
Q

Lidocaine

A

Alternative if allergic to ester type
Faster, intenser, longer-lasting, more extensive than Procaine
Anti-arrhythmic

32
Q

Procaine

A

Lower potency, slower onset, shorter duration
INFILTRATION ANESTHESIA ONLY
Metabolite (PABA) inhibits sulfonamide antibiotics

Neurology 2 (22 decks)

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