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Mar: prep for clinicals > 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

Protein Binding percentages for Bupivacaine, Lidocaine, and Prilocaine?

A

Bupivacaine - 95%
Lidocaine - 70%
Prilocaine - 55%

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15
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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16
Q

What is the bolus dose of Lipid Emulsion?

A

1.5 mL/kg of 20% lipid emulsion

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17
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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18
Q

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

A

8 mL/kg

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19
Q

What preservative commonly used for amide local anesthetics can be responsible for allergies?

A

Methylparaben

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20
Q

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

A

Pregnancy = ↓ plasma cholinesterases and also decrease in plasma proteins

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21
Q

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

A

Hyperventilation = ↓ CO₂ = ↓ acidosis

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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.

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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

27
Q

Cocaine
Peak:
Duration:
Elimination:

A

Peak: 30 to 45 mins
Duration: 60 mins after peak
Elimination - Urine

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

Drug V will be more ionized at physiological pH.

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

LA will be more non-ionized at physiological pH.

30
Q

Lidocaine
Metabolism:
Metabolite:
Max Dose:

A

Metabolism: Oxidative dealkylation in liver
Metabolite: Xylidide
Max Dose: 300 mg alone and 500 mg w/ Epi

31
Q

Prilocaine
Metabolite:
Max Dose:

A

Metabolite: Orthotoluidine
Max Dose: 600 mg
Converts hemoglobin to methemoglobin

32
Q

Methylene Blue
Indication:
Dose:

A

Indication: Methemoglobinemia
Dose: 1 to 2 mg/kg IV over 5 mins
Total dose not to exceed 7 to 8 mg/kg over 24 hours

33
Q

Bupivacaine and Ropivacaine bind to which protein?

A

α1-acid glycoprotein

34
Q

Benzocaine
Onset:
Duration:
Max Dose:

A

Onset: Rapid
Duration: 30 to 60 mins
Max Dose: 200 to 300 mg spray

35
Q

Procaine
Potency?
Maximum Single Dose?
pK?
Protein Binding?

A

Potency - 1
Maximum Single Dose - 500 mg
pK - 8.9
Protein Binding - 6%

36
Q

Chloroprocaine
Potency?
Maximum Single Dose?
pK?
Protein Binding?

A

Potency - 4
Maximum Single Dose - 600 mg
pK - 8.7
Protein Binding… no number was given.

Also has a rapid onset

37
Q

Tetracaine
Potency?
Maximum Single Dose?
pK?
Protein Binding?

A

Potency - 16
Maximum Single Dose - 100 mg (topical)
pK - 8.5
Protein Binding - 76%

38
Q

Lidocaine
Potency?
Maximum Single Dose?
pK?
Protein Binding?

A

Potency - 1
Maximum Single Dose - 300 mg
pK - 7.9
Protein Binding - 70%

39
Q

Prilocaine
Potency?
Maximum Single Dose?
pK?
Protein Binding?

A

Potency - 1
Maximum Single Dose - 400 mg
pK - 7.9
Protein Binding - 55%

40
Q

Mepivacaine
Potency?
Maximum Single Dose?
pK?
Protein Binding?

A

Potency - 1
Maximum Single Dose - 300 mg
pK - 7.6
Protein Binding - 77%

41
Q

Bupivacaine
Potency?
Maximum Single Dose?
pK?
Protein Binding?

A

Potency - 4
Maximum Single Dose - 175 mg
pK - 8.1
Protein Binding - 95%

42
Q

Levobupivacaine
Potency?
Maximum Single Dose?
pK?
Protein Binding?

A

Potency - 4
Maximum Single Dose - 175 mg
pK - 8.1
Protein Binding - > 97%

43
Q

Ropivacaine
Potency?
Maximum Single Dose?
pK?
Protein Binding?

A

Potency - 4
Maximum Single Dose - 200 mg
pK - 8.1
Protein Binding - 94%

44
Q

Eutectic Mixture of LA (EMLA) dose components and dosage?

A

Lidocaine 2.5% and Prilocaine 2.5%
1 to 2 grams/10 cm^2 area

45
Q

For subarachnoid blocks, dosing for a a 5ft person is ____ of 0.75% Bupivacaine… how much do you increase for each inch above 5ft?

A

1 ml
Increase by 0.1 mL/inch over 5 ft.

46
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
47
Q

Compute 1:500,000 Epi to mcg/mL

A

1,000,000/ 500,000=2

2 mcg/mL

48
Q

Compute 1:10,000 Epi to mcg/mL

A

1,000,000/ 10,000 = 100

100 mcg/mL

49
Q

0.5% equates to how many milligrams per milliliter?

A

5 mg/mL

50
Q

2% equates to how many milligrams per mL ?

A

20 mg/mL

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

51
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%

52
Q

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

A

Proximal comes back first & then distal.

53
Q

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

A

pK

54
Q

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

A

dose

55
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)
56
Q

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

For SAB, the ____ effect is 2 spinal segments caudal the sensory block.

A

SNS

Motor

Mar: prep for clinicals (16 decks)

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