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NBDE II > ORAL SURGERY Local Anesthesia > Flashcards

ORAL SURGERY Local Anesthesia Flashcards

1
Q

___ is a drug that reversibly blocks the conduction of nerve impulses when applied locally in a concentration without toxic effects. if the concentration is sufficient, motor nerves can be blocked as well

A

local anesthetics

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2
Q

what is the concept of “critical length” in nerve blockades?

A
  • complete anesthesia occurs when 3 consecutive nodes of ranvier are blocked (assuming myelinated)
  • the blockade can be cumulative along the axon length, resulting in gradual reduction in conduction velocity that eventually leads to a complete blockade
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3
Q

T or F:

not all nerves are susceptible to blockade

A

false, all nerves are susceptible to blockade, regardless of their function

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4
Q

sensations disappear and reappear in a definite order. what is that order?

A
  1. pain
  2. temperature
  3. touch
  4. pressure
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5
Q

what is redistribution affected by?

A
  • diffusion away from the site of action
  • vascularity of the injection site
  • protein binding characteristics of the local anesthetic that are directly related to lipid solubility
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6
Q

if the injection site has increased blood flow, what happens to the duration of action?

A

shorter

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7
Q

if the local anesthetic has increased protein binding characteristics, what happens to the duration of action?

A

increased lipid solubility, leading to increased duration of action

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8
Q

duration of action of local anesthetics is directly proportional to ___ and ___

A

protein binding and lipid solubility

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9
Q

what is the onset of action of a local anesthetic based on?

A
  • pKa

- the lower the pKa (closer to physiologic pH), the faster the onset of action

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10
Q

what are the initial clinical signs and symptoms of mild to moderate local anesthetic toxicity?

A

talkativeness, apprehension, excitability, slurred speech, dizziness, and disorientation

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11
Q

what are the initial clinical signs and symptoms of severe local anesthetic toxicity?

A

seizures, respiratory depression, coma, and death

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12
Q

what are allergic responses to local anesthetics due to?

A
  • esters (high incidence of 5% of the population)
  • amides (low incidence, <1%)
  • metabisulfite (low incidence)
  • allergies prior to 1985 may have been due to methylparaben
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13
Q

what is metabisulfite?

A
  • antioxidant in local anesthetics that protects the vasoconstrictor from oxidation
  • present only in LA cartridges with a vasopressor (epinephrine or levonordefrin)
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14
Q

methomoglobinemia is essentially unique to which local anesthetic? what dose can cause methomoglobinemia?

A
  • prilocaine
  • excess of 600mg (for a 70 kg adult)
  • lower dose applies in a patient with hereditary methomoglobinemia
  • second most common anesthetic to cause this is articaine
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15
Q

T or F:

when used for inferior alveolar nerve blocks, some local anesthetics are superior to others in terms of efficacy

A

false, they are all have equal efficacy, there is no one local anesthetic that has been shown to be superior

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16
Q

how have local anesthetic manufacturers adjusted drugs in terms of potency and toxicity?

A

concentration has been adjusted so that toxicity of 1mL of drug “A” is equivalent to 1mL of drug “B”

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17
Q

for two drugs that reach the same therapeutic effect per volume, a drug in 1mg/mL is more/less potent than a drug in 2mg/mL

A

more

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18
Q

___ is the most potent local anesthetic packaged for dentistry, and ___ and ___ are the least potent

A
  • bupivacaine

- prilocaine and articaine

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19
Q

what is the primary rationale for adding vasoconstrictors to local anesthetics?

A

increase duration of effect

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20
Q

what are the secondary rationales for adding vasoconstrictors to local anesthetics?

A

reduce systemic toxicity by decreasing the rate of systemic absorption of a given dose of LA and reduce bleeding by decreasing blood flow into the operative area

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21
Q

what are the drug interactions for local anesthetics and antidepressants?

A
  • increased sensitivity to epinephrine

- antidepressants = tricyclic (amytriptyline, elavil) and newer atypical drugs (duloxetine, cymbalta)

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22
Q

what are the drug interactions for local anesthetics and nonspecific beta blockers?

A
  • enhance peripheral alpha 1 adrenergic effects with beta 2 blockade (unopposed alpha)
  • blockade decreases heart rate
  • epinephrine increases blood pressure
  • the net result is likely to be an increase in blood pressure without tachycardia
  • nonspecific beta blockers = propranolol, inderal
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23
Q

in a normal, healthy patient, what is the maximum dose of epinephrine? what about for patients with cardiovascular compromise or pts taking tricyclic or atypical antidepressants or nonselective beta blockers?

A
  • 200ug for the healthy pt

- limit to 40ug per appointment for compromised pts

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24
Q

what are the pregnancy class C drugs (increased risk)?

A

articaine, bupivacaine, mepivacaine, epinephrine

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25
Q

what are the pregnancy class B drugs (no risk)?

A

lidocaine, prilocaine

26
Q

what is the safest local anesthetic for use in children if the safety is based on the number of mL that may be administered to a pediatric patient of a given size?

A

2% lidocaine w/1:100,000 epi

27
Q

which local anesthetic is contraindicated in children?

A

bupivacaine (not approved for use in children under 12 years)

28
Q

what is the pKa and max recommended dose of articaine 4%?

A

pKa 7.7, MRD 7mg/kg

29
Q

what is the pKa and max total dose of bupivacaine 0.5%?

A

pKa 8.1, MTD 90mg

30
Q

what is the pKa and max recommended dose of lidocaine 2%?

A

pKa 7.7, MRD 7mg/kg

31
Q

what is the pKa and max recommended dose of mepivacaine 2%, 3%?

A

pKa 7.6, MRD 6.6mg/kg

32
Q

what is the pKa and max recommended dose of prilocaine 4%?

A

pKa 7.8, MRD 8mg/kg

33
Q

short needles average ___mm and long needles average ___mm

A

20mm, 32mm

34
Q

what are the outside diameters of the most common gauged needles?

A

30 gauge averages 0.3mm
27 gauge averages 0.4mm
25 gauge averages 0.5mm

35
Q

positive aspiration is directly correlated to ___

A

needle gauge

36
Q

T or F:

larger gauge needles deflect more often

A

false

37
Q

about 97% of needle breaks involved breakage of which gauge needle?

A
  • 30 gauge

- larger gauge needles do not break as often

38
Q

can patients tell the difference in feel between 25, 27, and 30 gauge needles?

A

no

39
Q

what is the area of anesthesia for the posterior superior alveolar (PSA) nerve block?

A

from the maxillary third molar anteriorly to the maxillary first molar with the possible exception of the mesiobuccal aspect of the maxillary first molar

40
Q

describe the technique (needle position) of the PSA block

A
  • position the needle distal to the malar process
  • at 45 degrees to the mesiodistal plane
  • at 45 degrees to the buccolingual plane
  • 15-16mm depth of penetration
  • deposit 1mL of local anesthetic slowly after aspiration
41
Q

what is the area of anesthesia for a true anterior superior alveolar (ASA) nerve block?

A
  • from the midline of the maxilla to the mesiobuccal aspect of the maxillary first molar
  • anesthetizes the ASA, MSA, inferior palpebral, lateral nasal, and superior labial nerves
42
Q

describe the technique of the true ASA nerve block

A
  • needle penetration is over the maxillary first premolar in the long axis of the tooth
  • 15mm deep and lateral to or at the height of the buccal vestibule
  • needle touches bone as an endpoint
  • after aspiration, 0.9mL is injected slowly
  • pressure is applied for 2 minutes
  • first 4 steps describe the infraorbital nerve block (does not guarantee tooth anesthesia); the last step makes it a true ASA nerve block
43
Q

what is the area of anesthesia for the greater palatine block?

A

on the palate from the canine distally to the posterior aspect of the hard palate and from the gingival margin to the midline

44
Q

the greater palatine foramen is generally located where?

A

roughly halfway between the gingival margin and midline of the palate and approximately 5mm anterior to the junction of hard and soft palate

45
Q

what is the technique for the greater palatine nerve block?

A
  • topical anesthesia
  • pressure anesthesia for at least 20 seconds
  • angulation of the needle insertion is immaterial
  • depth of penetration is to bone (about 5mm)
  • inject 0.5mL after aspiration
46
Q

what is the area of anesthesia for the nasopalatine nerve block?

A

palatal soft tissue from canine to canine, bilaterally (premaxilla)

47
Q

what is the technique for the nasopalatine nerve block?

A
  • topical anesthesia
  • pressure anesthesia for at least 20 seconds
  • needle tip at 45 degree angle to the palatal soft tissue; penetration is at the junction of the palate and incisive papilla
  • endpoint is bone
  • inject 0.5mL after aspiration
48
Q

what is the area of anesthesia for the mental nerve block?

A

soft tissue on the buccal of the premolars anteriorly to the midline lip, chin, periosteum, and bone in the affected area

49
Q

what is the technique for the mental/incisive nerve block?

A
  • topical anesthesia
  • insert needle in the depth of the buccal vestibule opposite the mandibular premolars
  • 5mm depth of insertion
  • deposit 0.9mL local anesthetic
  • pressure for 2 minutes
  • steps 1-4 are for the mental block, which is soft tissue only. the last step makes it an incisive nerve block and anesthetizes the teeth
50
Q

what is the area of anesthesia for the inferior alveolar nerve block?

A

pulps and buccal soft tissues of the mandibular teeth (except the area innervated by the buccal nerve), lip, chin, periosteum, and bone in the affected area

51
Q

what is the anatomic target for the traditional (halstead) IA block?

A
  • approach from contralateral premolars
  • 1cm above the mandibular occlusal plane and parallel to it
  • with a needle endpoint 50% of the mesiodistal length of the ramus, distally
52
Q

what is the anatomic target for the higher mandibular block?

A
  • approach from the contralateral premolars
  • 1.5cm above the mandibular occlusal plane and parallel to it
  • with a needle endpoint of 60% of the mesiodistal length of the ramus, distally
53
Q

what is the technique for the IA nerve block (works for either traditional or higher targets)?

A
  • advance a 25 gauge log needle until you hit bone (required), withdraw 1mm and aspirate
  • inject 1.5mL of LA over 2 minutes
  • withdraw the needle halfway (approx 10-15mm) and aspirate
  • slowly inject the lingual nerve
  • save a few drops of anesthetic for the long buccal nerve if needed
54
Q

what nerves does the vazirani akinosi technique block?

A

inferior alveolar, lingual, long buccal

55
Q

the vazirani akinosi technique is useful for treating which patients?

A

uncooperative children and patients with trismus

56
Q

what is the technique for the vazirani akinosi block?

A
  • long needle is inserted parallel to the maxillary occlusal plane at the level of the maxillary buccal vestibule
  • depth of penetration is approx 1/2 the mesiodistal length of the ramus (about 25mm in adults, less in children)
  • this endpoint is just superior to the lingula
  • the injection is performed blindly because no bony endpoint exists
  • in adult patients, a rule of thumb is that at the depth of needle penetration, the hub of the needle should be between the maxillary first and second molars
57
Q

the original gow gates technique involved only ___ landmarks

A

extraoral

58
Q

what nerves does the gow gates block anesthetize?

A

IA, lingual, auriculotemporal, mylohyoid, and long buccal (75% of the time)

59
Q

what is the technique for the gow gates block?

A
  • beginning from the contralateral canine, the needle is positioned so that a puncture point is made approx at the location of the distobuccal cusp of the maxillary second molar
  • needle is inserted to a depth of 25-30mm until bone is contacted (required), then withdraw slightly and inject entire cartridge after aspiration
60
Q

what is the pre-insertion technique for the gow gates block?

A
  • have the patient open their mouth as widely as possible to rotate and translate the condyle forward
  • the condyle is palpated with the fingers of the nondominant hand while the cheek is retracted with the thumb
61
Q

which injection is unique among intraoral injections because the operator does not attempt to get as close as possible to the nerve to be anesthetized?

A
  • gow gates
  • the needle tip should be approximately 1cm directly superior to the nerve, in the superior aspect of the pterygomandibular space

NBDE II (35 decks)

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