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Dermatology Board Prep > DERM (23) Surgery > Local anesthetics and perioperative pain control > Flashcards

Local anesthetics and perioperative pain control Flashcards

1
Q

What are the 3 main types of afferent sensory fibers?

A
  • C fibers: small diameter, unmyelinated
  • Adelta: medium diameter, lightly myelinated
  • Abeta: Large, fast-conducting, myelinated fibers
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2
Q

What type of pain do c, Adelta, and Abeta fibers, transmit?

A

C: diffuse, dull, and aching pain

Adelta: Sharp, localized pain and temperature

Abeta: vibration and light pressure

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3
Q

What afferent sensory fibers respond quickest to lidocaine?

A

C fibers>Adelta>Abeta

The Abeta ones take awhile –> leads to the pt to feel something but not pain (pressure, movement)

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4
Q

What are the two broad groups of local anesthetics?

A

Amides (most common) and Esters

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5
Q

How are amides vs ester local anesthetics metabolized?

A
  • Amides: Metabolized in the liver via the CYP 3A4 system in the liver
  • Ester: Metabolized via pseudocholinesterases in the plasma; renally excreted
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6
Q

What is an easy way to identify an amide vs an ester local anesthetic?

A

If the drug name has two “i’s” = Amides (ex lidocaine, prilocaine, etc)

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7
Q

What is the most likely component of an amide anesthetic to cause an allergic reaction?

A

Methylparaben preservative

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8
Q

What should be done if an allergic reaction to an amide anesthetic occurs?

A

Most likely from the preservative (methylparaben) –> switch to preservative-free lidocaine

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9
Q

What is the most common allergen in allergies to ester anesthetics?

A

PABA

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10
Q

If a pt is allergic to an ester anesthetic, what else will they likely be allergic to?

A

PABA (frequent allergen in ester anesthetics) crossreact with the “PPPESTAA” allergens: Paraphenylenediamine (PPD), PABA, Para-aminosalicylic acid, Ethylenediamine, Sulfonamides, Thiazides, Anesthetics (esters), Azo dyes

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11
Q

What are contraindications to amide anesthetic usage?

A

End-stage liver disease

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12
Q

What are some contraindications to ester anesthetics?

A

Allergy to PABA or cross-reacting substances, pseudocholinesterase deficiency, and renal insufficiency

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13
Q

Is there any difference in efficacy between 1:200,000 vs 1:100,000 epinephrine in anesthetic?

A

No! These are equally effective and the more dilute (1:200,000) formulation has less toxicity

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14
Q

What are the contraindications for the usage of epinephrine in local anesthetics?

A

pheochromocytoma, and uncontrolled hyperthyroidism

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15
Q

Should local anesthetic + epinephrine be used on patients that are pregnant?

A

Can cause decreased uterine blood flow (pregnancy category C)

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16
Q

In what situations should epinephrine be used with caution in local anesthetics?

A

Pregnancy, severe CV disease, HTN, glaucoma, and drugs (B-blockers, TCAs, and MAO-I)

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17
Q

How does addition of sodium bicarbonate (8.5%) change anesthetic properties?

A

Bicarb raises pH to near physiologic levels –> majority of anesthetic remains natural/uncharged which allows the anesthetic to more rapidly cross nerve membranes

Speeds onset and decreases injection pain

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18
Q

What are the disadvantages of adding sodium bicarbonate to local anesthetic?

A

Decreased shelf-life (due to epinephrine degradation)

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19
Q

What impact does the addition of hyaluronidase to local anesthetic do?

A

Degrades hyaluronic acid, increases anesthetic diffusion and tissue distortion from fluid infiltration

Disadvantages: decreases the duration of anesthesia and anesthetic toxicity as a result of increased absorption and also contain contact allergy thimerosal

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20
Q

If a pt gets a reaction to lidocaine with hyaluronidase added, what is the most likely allergen?

A

Thimerosal

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21
Q

What are the adult maximum doses of lidocaine (w/o epinephrine, w/ epinephrine, and tumescent)?

A

4.5-5mg/kg, 7mg/kg, 55mg/kg

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22
Q

What are the pediatric maximum doses of lidocaine (w/o epinephrine, w/ epinephrine, and tumescent)?

A

1.2-2mg/kg, 3-4.5mg/kg, (tumescent not used)

these are approx. half of adult doses

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23
Q

What is the fastest onset local anesthetic?

A

Lidocaine (onset in <1min)

24
Q

Which local anesthetic has the slowest onset of action?

A

Mepivacaine

25
Q

What is the local anesthetic of choice in pregnant women?

A

Lidocaine

26
Q

Which local anesthetic carries a risk of methemoglobinemia and why is this important to remember?

A

Prilocaine, risk highest in those w/ G6PD and those <1y/o

Important b/c it is in the commonly used EMLA topical anesthetic

27
Q

What two amide local anesthetics should not be used in pregnancy and why?

A

Mepivacaine: fetal bradycardia

Bupivacaine: fetal bradycardia

28
Q

What is the longest activing amide anesthetic?

A

Bupivacaine (if combined w/ epi) –> often added to lido for long mohs cases

Ropivacaine is the longest acting anesthetic w/o epi

29
Q

What are the sx’s of mild lidocaine overdose?

A

*sx’s loosely follow EtOH toxicity

Mild = restlessness, euphoria, talkativeness, lightheadedness, “funny tingling” around mouth/hands, metallic taste, and circumoral numbness

30
Q

What are the sx’s of moderate lidocaine toxicity?

A

Nausea, vomiting, psychosis, tinnitus, muscle twitching/tremors, blurred vision, slurred speech, and confusion

31
Q

What are the sx’s of severe lidocaine toxicity?

A

Seizures and cardiopulmonary depression

32
Q

What is the easiest way to differentiate anaphylaxis and vasovagal responses to anesthesia?

A

Compare HR and BP

Vasovagal: Low pulse low BP

Analaphylaxis: high pulse/low BP (shock)

33
Q

What intervention should be performed for mild lidocaine toxicity?

A

Observation

34
Q

What intervention should be performed for moderate lidocaine toxicity?

A

Diazepam; airway maintenance

35
Q

Management for severe lidocaine toxicity?

A

Respiratory support, cardiopulmonary support, life support, etc –> advanced care setting

36
Q

What intervention should be done for vasovagal reaction?

A

Trendelenburg, cold compress and reassurance

37
Q

What are the signs/sx’s of vasovagal reactions?

A

Excess parasympathetic reaction; diaphoresis, hyperventilation, and nausea

38
Q

What are the sx’s of excessive epinephrine dosing?

A

Alpha and Beta receptor stimulation: palpitations, muscle tremors, and nervousness

39
Q

What occurs with the BP and HR of epinephrine overdose?

A

High HR and high BP

40
Q

What is the intervention for epinpehrine overdose?

A

Usually just observation (resolves in minutes). Severe cases: phentolamine and propranolol

41
Q

What is the maximum amount of lidocaine + epi that should be used on a digital block?

A

3 mL on each side (6 mL in total)

42
Q

What does EMLA stand for?

A

Eutectic mixture of local anesthesia

43
Q

What anesthetics are in EMLA?

A

2.5% prilocaine and 2.5% lidocaine

44
Q

What are some cautions for using EMLA?

A

Can cause methemoglobinemia (in infants and those w/ G6PD from prilocaine) and can cause corneal injury (don’t use near eye)

45
Q

What histologic changes can EMLA cause?

A

Artificial swelling and vacuolization of upper epidermis and basal layer split

46
Q

What is the only anesthetic that causes vasoconstriction?

A

Cocaine (esther) –> this is why epi is used in the others, they cause vasodilation

47
Q

What topical anesthetics are used for eye numbing?

A

Proparacaine and tetracaine

48
Q

What topical ester anesthetic is often used on the mucosa?

A

Benzocaine

49
Q

When is post-operative pain worst after a procedure?

A

The night of the surgery day, drops dramatically each additional day after surgery

50
Q

What should be considered if pain persists for >4 days after surgery?

A

Consider infection, hematoma, or drug-seeking behavior

51
Q

What is the most common concentration of epinephrine in lidocaine?

A

1:200,000

52
Q

What concentration of epinephrine is used in tumescent lidocaine?

A

1:1 million

53
Q

What area is injected for an ulnar nerve block?

A

Just lateral to flexor carpi ulnaris

54
Q

Which anesthetics are most likely to be cardiotoxic?

A

Bupivicaine (most) and ropivacaine (second)

55
Q

What are two preservatives that can cause allergy in amide anesthetics?

A

Sodium metabisulfite and methyl-paraben

56
Q

What topical anesthetic is most likely to cause contact dermatitis?

A

Benzocaine

57
Q

What is the order of sensation loss when an anesthetic is injected?

A

Temperature, pain, touch, pressure, vibration, proprioception, motor

DERM (23) Surgery (12 decks)

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