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Clinical Prep > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

1
Q

What local anesthetic class is responsible for more allergic reactions?

A

Esters (due to PABA metabolite)

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2
Q

What is LAST?

A

Local Anesthetic Systemic Toxicity

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3
Q

What causes LAST syndrome?

A

Excess plasma concentration of LA from:

  • Accidental IV injection
  • Systemic absorption from tissue redistribution and clearance metabolism.
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4
Q

What factors affect the magnitude of systemic absorption of local anesthetic?

A
  • Dose
  • Vascularity of site
  • Concurrent Epi use
  • Properties of the drug itself
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5
Q

Would local anesthetic administered via the trachea have a higher or lower chance of systemic absorption than local anesthetic delivered brachially?

A

Trachea has higher chance of systemic absorption.

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6
Q

What serum electrolyte condition will exacerbate local anesthetic toxicity?
Why?

A

Hyperkalemia (lowers seizure threshold)

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7
Q

What s/s would be seen with a plasma lidocaine concentration of 1-5 mcg/ml?

A

Analgesia

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8
Q

What s/s would be seen with a plasma lidocaine concentration of 5-10 mcg/ml?

A
  • Mouth numbness
  • Tinnitus
  • Muscle twitching
  • ↓BP
  • Myocardial depression
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9
Q

What s/s would be seen with a plasma lidocaine concentration of 10-15 mcg/ml?

A
  • Seizures
  • Unconsciousness
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10
Q

What s/s would be seen with a plasma lidocaine concentration of 15-25 mcg/ml?

A
  • Apnea
  • Coma
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11
Q

What s/s would be seen with a plasma lidocaine concentration of >25 mcg/ml?

A

Cardiovascular Depression

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12
Q

How does lidocaine affect EKGs?
How does it do this?

A
  • Prolongation of PR interval and QRS widening.
  • Blockade of Na⁺ channels
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13
Q

Which three drugs are most responsible for cardiac adverse effects when reaching toxic levels systemically?

A

Bupivacaine > Ropivacaine > Lidocaine

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14
Q

How does Lipid Emulsion rescue work?

A

Lipids encapsulate the local anesthetic and transport it away from cardiac and CNS tissue.

Also provides fat for myocardial metabolism.

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15
Q

What is the bolus dose of Lipid Emulsion?

A

1.5 mL/kg of 20% lipid emulsion

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16
Q

What is the infusion dose of lipid emulsion?
How long should it be given?

A

0.25 mL/kg/minute for at least 10 minutes

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17
Q

What is the max dose for lipid emulsion that should be given?

A

8 mL/kg

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18
Q

What preservative commonly used for amide local anesthetics canbe responsible for allergies?

A

Methylparaben

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19
Q

Why does pregnancy predispose one to cardiovascular toxicity from LA’s?

A

Pregnancy = ↓ plasma cholinesterases

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20
Q

Which two factors predispose our OB population to local anesthetic toxicity?

A
  • ↓ plasma esterases
  • ↓ plasma proteins
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21
Q

Should a local anesthetic toxicity patient be hyperventilated or hypoventilated?
Why?

A

Hyperventilation = ↓ CO₂ = ↓ acidosis

22
Q

If cardiac arrest occurs with LAST syndrome, how should our epinephrine dosing change?

A

Small doses (10mcg - 100mcg boluses) are preferred with LAST ACLS.

23
Q

How much vasopressin should be given if a patient is suffering from hypotension from LAST syndrome?

A

Trick question. Vasopression should not be given with LAST syndrome.

24
Q
A

56kg so 1.5mLs x 56kg = 84mLs

20% infusion = 200mgs / 1mL

84mLs x 200mgs = 16,800mgs administered

25
Q

What is Cocaine’s MOA?

A

Blocks presynaptic re-uptake of NE and Dopamine → Increases postsynaptic levels and ↑SNS.

26
Q

What drug is best for treating cocaine toxicity?

A

Nitroprusside

28
Q

If Drug V (weak base) has a pKa of 9.1, will the drug be more ionized or nonionized at physiological pH?

A

pKa - pH
9.1 - 7.4 = +1.7

Drug V will be more ionized at physiological pH.

Weak Bases, pKa before pH
Weak Acids, pKa afterpH

29
Q

If the pKa of LA (a weak base) is at 4.5, will the drug be more ionized or nonionized at physiological pH?

A

pKa - pH
4.5 - 7.4 = -2.9

LA will be more non-ionized at physiological pH.

Weak Bases, pKa before pH
Weak Acids, pKa afterpH

30
Q

LA1’s pKa is 9.2, and LA2’s pKa is 7.5. Which of the following are correct when placed in physiological pH? Select 2 answers.

A. LA2 has more non-ionized components
B. LA1 has more ionized components
C. LA2 has more ionized components
D. LA1 has more non-ionized components

A

B and C

LA1
9.2 - 7.4 = +1.8 (ionized)

LA2
7.5 - 7.4 = +0.1 (ionized)

Weak Bases, pKa before pH
Weak Acids, pKa afterpH

31
Q

What is epinephrine 1:200,000 mean?

Convert that to mcg/mL.

A

1:200,000 means 1 gram of epinephrine is dissolved in 200,000 mL of solvent.

  • 1g/200,000 mL
  • 1000mg/200,000 mL
  • 1 mg/200 mL
  • 1000 mcg/200 mL
  • 10 mcg/2 mL
  • 5 mcg/mL
32
Q

Compute 1:500,000 to mcg/mL

A

2 mcg/mL

  • 1 g/500,000 mL
  • 1000 mg/500,000 mL
  • 1 mg /500 mL
  • 1000 mcg/500 mL
  • 10 mcg/5 mL
  • 2 mcg/mL

Shortcut: 1,000,000 divided by the solvent number. 1 million/500,000 = 2 mcg/mL

33
Q

Compute 1:500,000 Epi to mcg/mL

A

1,000,000/ 500,000=2

2 mcg/mL

34
Q

Compute 1:10,000 Epi to mcg/mL

A

1,000,000/ 10,000 = 100

100 mcg/mL

35
Q

Compute 1:1000 Epi to mcg/mL

A

1,000,000/ 1000 = 1000

1000 mcg/mL

36
Q

0.25% equates to how many mg per mL ?

37
Q

0.5% equates to how many milligrams per milliliter?

38
Q

1% equates to how many milligrams per mL ?

39
Q

2% equates to how many milligrams per mL ?

A

20 mg/mL

2% lidocaine is the most common concentration used in the OR

40
Q

4% equates to how many milligrams per mL ?

41
Q

112.5 mg of Bupivacaine with Epi and 250 mg of Lidocaine with Epi were given during surgery.

What are the percentages of each LA based on the recommended max single dose in mg?

A

Max single dose of Bupivacaine with Epi: 225 mg
112.5/225 = 50%

Max single dose of Lidocaine with Epi: 500 mg
250/500 = 50%

42
Q

When the peripheral nerve block is wearing off, what comes back first? Proximal or Distal?

A

Proximal comes back first & then distal.

43
Q

Peripheral Nerve Block onset of action is dependent on the local anesthetic’s _________.

44
Q

The duration of a peripheral nerve block depends on the _____ of the local anesthetic.

45
Q

What is the sequence of blockades for a segmental block in Neuraxial Anesthesia?

A
  1. SNS (Myelinated preganglionic B fibers)
  2. Sensory (Myelinated A, B fibers, unmyelinated C fibers)
  3. Motor (Myelinated A-δ and unmyelinated C fibers)
46
Q

For SAB, the _______ effect is 2 spinal segments cephalad of the sensory block.

For SAB, the _______ effect is 2 spinal segments below the sensory block.

47
Q

What can be added to LA so that its specific gravity can increase?

What can be added to LA so that its specific gravity can decrease?

A

Glucose added → hyperbaric solution.

Distilled water added → hypobaric solution

48
Q

Regarding weak bases, the pKa is ________ pH.

A

before

ex. pKa 9, pH 7 → 9 - 7 = +2

49
Q

Regarding weak acids, the pKa is ________ pH.

A

after

ex. pKa 9, pH 7 → 7 - 9 = -2

50
Q

Nicely negative numbers are _________.

A

non-ionized

Clinical Prep (11 decks)

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