Local Anesthetics Flashcards

1
Q

Esters

A
  • cause more hypersensitivity reactions

- only 1 letter “i”

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2
Q

Ester durations and potency

A

Short: Procaine (1)
Long: Tetracaine (16)
Topical/Surface: Benzocaine, cocaine (2)

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3
Q

Amides

A

-2 letter “i”s

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4
Q

Amides duration and potency

A

medium: lidocaine (4), mepivacaine (2)

Long: bupivacaine (16), ropivacaine (16)

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5
Q

Esters: Onset and duration

A
  1. Procaine:
    onset: 2-5min
    duration: 25 min to 1 hour
  2. Tetracaine
    onset: <15 min
    duration: 2-3 hours
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6
Q

Amides: onset and duration

A
  1. Mepivacaine
    onset: 3-5 min
    duration: ~1hr
  2. Bupivacaine
    onset: 5 min
    duration: 2-4 hrs
  3. Lidocaine
    onset: <2min
    duration: 30min - 1hr
  4. Ropivacaine
    onset: 10-30min
    duration: ~30min
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7
Q

Local anesthesia MOA

A

block voltage-dependent sodium channels of excitable membrane from sending sensory info to the CNS

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8
Q

Which form of local anesthetic is better/faster at crossing the lipid membrane to reach the cytoplasm receptor site?

A

Non-ionized form

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9
Q

Which form of local anesthetic is the more effective blocking entity once inside the axon?

A

Ionized form

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10
Q

What effect does sodim bicarbonate have when added to a local anesthetic?

A
  1. Accelerates the onset of action

2. Decreases burning sensation

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11
Q

What effect does adding epinephrine (alpha agonist sympathomimetic vasoconstrictor) to a local anesthetic?

A

prolongs duration

long acting don’t need this - bupivicaine, ropivicaine, tetracaine and neither do topical local anesthetics

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12
Q

What is the difference in esters and amides when it comes to metabolism?

A

Esters - metabolized in the blood by plasma cholinesterases (very rapid)

Amides -metabolized by liver (so, higher risk of liver toxicity with liver dysfunction)

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13
Q

What type of fiber would be most easily blocked?

A

a small myelinated fiber

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14
Q

What type of fiber would be most difficult to block?

A

a large unmyelinated fiber

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15
Q

Which type of fiber is hardest to block?

A

Type A - Alpha (proprioception, motor)

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16
Q

Which type of fiber is easiest to block?

A

Types B, C and Type A - delta (pain, temperature)

17
Q

Which would be blocked first a medium myelinated fiber or a small unmyelinated fiber?

A

the myelinated fiber

18
Q

A-alpha fiber

A
  • muscle proprioception
  • Largest fiber type
  • myelinated
19
Q

A-beta fiber

A
  • Second largest fiber
  • Touch
  • myelinated
20
Q

A-delta fiber

A
  • 3rd largest fiber
  • pain and temperature
  • myelinated
21
Q

C-nerve fiber

A
  • Not myelinated
  • pain, temperature, itch
  • Small fiber
22
Q

Sequence of nerves to be blocked

A
  1. Sympathetic
  2. Temperature
  3. Pain
  4. Light touch
  5. Motor
23
Q

Epidural block

A

-local anesthetic extradurally

24
Q

Caudal block

A

-epidural block in the caudal canal via the sacral hiatus

25
Q

Spinal block

A

injection into cerebrospinal fluid in the subarachnoid space

26
Q

Why is bupivacaine banned by the FDA in obstetrics for epidural anesthesia?

A

cardiotoxicity

27
Q

How can you tell local anesthetics with and without epinephrine by the label on the bottle?

A

red label if it contains epi

28
Q

Amides local anesthetics

A

Pharmacokinetics: hepatic metabolism

  • bupivacaine is most likely to cause heart problems
  • CNS effects (light headed, sedation, restlessness, nystagmus, tonic-clonic convulsions
29
Q

Ester local anesthetics

A

Pharmacokinetics: rapid metabolism by plasma esterases

  • Metabolites can cause antibody formation
    ex. Benzocaine, cocaine, procaine, tetracaine
30
Q

Prilocaine: ADE

A

can convert hemoglobin to methemoglobin

31
Q

What medication is given to someone having a convulsion due to anesthetic toxicity?

A

Diazepam IV (Valium)