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NMSK Exam 3 > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

1
Q

Local anesthetics (6)

* for amides, rest are esters

A
    1. Benzocaine
    1. Bupivacaine *
    1. Cocaine
    1. Dibucaine
    1. Lidocaine *
    1. Procaine
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2
Q

Allergic reactions to what type of local anesthetics is most common due to metabolism of allergy-causing compounds?

How can you tell the type of local anesthetic based on its name?

A

Ester ( benzocaine, cocaine, procaine, and tetracaine)

*Will only have one ‘i’ in the name; while amides will have at least two ‘i’s

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3
Q

Local anesthetics that are amides

A

2 I’s

  1. Lidocaine
  2. Bupivacaine
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4
Q

Which local anesthetics are more prone to hydrolysis and as a result generally have a shorter duration of action?

A

-Esters

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5
Q

Use of which drugs will reduce systemic absorption of local anesthetics and is useful for those drugs with intermediate or short durations of action (ie., prolongation of action)?

A

Vasconstrictors (i.e., epinephrine) => helps to prolong action

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6
Q

Which type of local anesthetic is widely distributed after IV bolus administration?

A

Amide-type

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7
Q

How does the metabolism of ester-type local anesthetics differ from the amide-type?

A
  1. Ester-type = are metabolized in plasma
  2. Amide-type are metabolized in liver and then e_xcreted in urine as charged substances (CYP450)_
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8
Q

What is the MOA of local anesthetics?

Where is their receptor site located?

A

- Block VGNa+ channel currents => stop spread of AP’s.

  • Receptor site is at inner vestibule of the sodium channel
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9
Q

What structural properties of some local anesthetics cause a faster rate of interaction with the Na+ channel and more potent actions?

A

Smaller and more lipophilic (Bupivacaine) => more potent and faster rate of AXN

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10
Q

How does fiber diameter and degree of myelination affect the action of local anesthetics?

List an example

A

Preferentially block

  1. Small fibers
  2. Myelinated nerves (vs. unmyelinated nerves of the same diameter)

* Type A delta (pain/temp fibers) more susceptible to being blocked than larger Type A Alpha fibers (propioception/motor).

*Type B (preganglionic autonomic) fibers are blocked before smaller/unmyelinated C fibers

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11
Q

How does firing frequency affect the action of local anesthetics, which are preferntially blocked?

List an example

A

Higher frequencies of depolarization = blocked first

  • i.e., type A delta (pain and temperature) and C (dorsal root/sympathetic) fibers are blocked earlier than large (propioveption/motor) A alpha fibers
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12
Q

Sensory or motor: Which is affected first by local anesthetics when injected into a bundle of large mixed nerves?

A

MOTOR

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13
Q

How does the position of sensory fibers within the extremites change from proximal to distal limbs?

A
  • Proximal sensory fibers = located in outer portion of nerve trunk (will be affected first by local anesthetic)
  • Distal sensory fibers = located in the core of the nerve trunk (motor fibers will be affected first)
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14
Q

Local anesthetics can be administered topically, injection OR IV regional anesthesia (Bier Block).

What are the 4 types of injections

A
  1. Infiltration anesthesia
  2. Block anesthesia
  3. Spinal anesthesia
  4. Epidural anesthesia
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15
Q

What is block anesthesia and its purpose?

A
  • Injection in major nerve trunks
  • Purpose is the anesthetize a region distal to the injection site
  • * femoral block = surgery distal to knee
  • * brachial plexus block = procedure of UE or shoulder
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16
Q

What is IV regional anesthesia (Bier block) used for?

How is it done?

A
  • Used for short surgeries (<60 min) involving UE and LE’s
  • IV injection of LARGE dose of local anesthetic in a distal vein + proximal tourniquet to isolate circulation of limb
  • Keep tourniquet on prevent high circulating drug levels causing systemic effects
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17
Q

What in infiltration anesthesia

A

inject directly into tissue next to a peripheral nerv_e,_ without taking into consideration the course of cutaneous nerve; can be superficial enough to include only skin or deep enough to include intraabdominal organs.

18
Q

What is spinal anesthesia

A
  • Inject into CSF in lumbar space => causes anesthesia over big part of body with a dose of local anesthestic that negligable in plasma
19
Q

What ROA is best for cathetiers that placed in epidural space , allowing continous infusion or repeated bolus admin

A

Epidural anesthia

20
Q

How does co-admin of vasoconstrictors + local anesthetics affect shit

A
  1. decreases rate the anesthesia is absorped into circulation and metaboliszed
  2. dec systemic toxicity
21
Q

Epinephrine administration to prolong the action of local anesthetics should never be injected into what tissues?

What could this result in?

A

Those supplied by end arteries

  • Fingers, toes, nose, and penis
  • Vasocontriction could cause gangrene
22
Q
  1. Which local anesthetic potentiates the effect of NE on α-adrenergic receptors by blocking NET and results in localized vasoconstriction?
  2. What does this do?
A
  1. Cocaine
  2. *Eliminates need for combining the drug w/ epinephrine
23
Q

What are the early signs of CNS toxicity caused by local anesthetics?

A
  1. Circumoral and tongue numbness
  2. Metallic taste
24
Q

High concentrations of local anesthetics in the CNS may have what adverse effects?

A
  1. Nystagmus
  2. Muscular twitching
  3. Convulsions
  4. Death by respiratory failure
25
Q

When large doses of local anesthetics are need, what can be given to prevent CNS toxicity by raising the the seizure threshold?

A

Parenteral Benzodiazepine (diazepam or midazolam)

26
Q

Undesired effects of local anesthetics on the CV system are the result of direct effects on ___________ and from indirect effects on the _____________

A

Undesired effects of local anesthetics on the CV system are the result of direct effects on cardiac and smooth muscle and from indirect effects on the ANS

27
Q

Local anesthetics block which ion channels in the heart => cause AE on the <3 and BP?

A
  • Block cardiac Na+ channels
    • ↓↓↓ electrical excitability, conduction rate, force of contraction
    • Arteriolar dilation —> systemic hypotension
28
Q

Cocaine is an exception to the local anesthetic effects on the heart, and instead can cause what?

A
    • Vasconstriction –> local ischemia
    • HTN
    • Cardiac arrhythmias
29
Q

Which local anesthetic is the most cardiotoxic?

Why?

A

Bupivacaine => longest duration of action

30
Q

Which local anesthetic is a Class Ib antiarrhythmic?

A

Lidocaine

31
Q

What are the effects of Lidocaine on the heart?

A
    • DEC automaticity of condunction tissue by increasing threshold of electrical stimulation of ventricle, His-Purkinje system, and spontaneous depolarization of the ventricles during diastole
    • Blocks both the initiation/ conduction of AP by decreasing the neuronal membrane’s permeability to Na+ ions, => no depolarization & blocks conduction
32
Q

What is Benzocaine used for?

A

Only as topical agent

  1. Dermatologic conditions,
  2. Hemorrhoids
  3. Premature ejaculation
  4. Anesthetic lubricant (NG an e_ndoscopic tubes/catheters_)
33
Q

Bupivacaine has a tendency to provide more of a (sensory or motor) block?

What else can it do due to its duration of action?

A

Sensory block

Long duration of action = prolonged anesthesia

34
Q

Cocaine, as a local anesthetic, is used primarily how?

A

Topical anesthtic of the upper respiratory tract

35
Q
  1. What is Lidocaine used for clinically?
  2. How does it compare to procaine?
A
  • Alternative pt’s with allergy to ester local anesthetics
  • Antiarrythmic agent

*Faster, more intense, longer acting, and more extensive anesthesia than an equal dose of Procaine

36
Q

What is Procaine used for clinically?

How does it compare to newer drugs?

A

Only for infiltration anesthesia (local anesthesia produced by injection of the anesthetic solution directly into the area of terminal nerve endings)

*less potent, slower onset, shorter duration of action*

37
Q

Which local anesthetic is metabolized to a para-aminobenzoic acid, which inhibits the action of sulfonamide ABX?

A

Procaine

38
Q

Low concentrations of local anesthetics may cause what adverse effects on the CNS?

A
  1. - Sleepiness (*CIS Q)
    • Restlessness
    • Light-headedness
    • Visual / auditory disturbances
39
Q

Which local anesthetic is for surface use only? Why?

A

Benzocaine = poor solubility in H20

*i.e., someone comes in with bad road rash or something

40
Q

Which 3 local anesthetics have long durations of action?

A
  1. Bupivacaine
  2. Ropivacaine
  3. Tetracaine
41
Q

Which local anesthetic has a short duration of action; used only for infiltration anesthesia?

A

Procaine

42
Q

What is the most potent local anesthetic vs least?

A
  • Most = Bupivacaine = long duration
  • Lease = Procaine = short duration

NMSK Exam 3 (17 decks)

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