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Anes. Pharm. Me > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

2
Q

What is the mechanism of local anesthetics?

A

LA block voltage gated sodium channels preventing the influx of sodium ions, thus preventing an action potential

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3
Q

Local anesthetics bind Na channels in the _______ state

A

activated

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4
Q

How do local anesthetics affect resting and threshold potentials?

A

not altered

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5
Q

Which nerves are more easily blocked?Myelinated or unmyelinated?small or large fibers?resting or rapidly firing channels?proximal or distal?

A

Easier:MyelinatedSmallrapidly firingproximal

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6
Q

What are the three groups in the LA molecule?

A

Lipophilic group (benzene ring) and hdyrophilic group (tertiary amine) linked together with either an ester or amide

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7
Q

Name the amide LAs

A

LidocainemepivacainePrilocaineBupivacaineRopivacaineEtidocainei before the caine

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8
Q

Name the ester linked LAs

A

Procaine Chloroprocainetetrocainecocainebenzocaine

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9
Q

Where are the amides metabolized?

A

liver

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10
Q

Where are esters metabolized? Exception?

A

esters are metabolized by plasma cholinesterases, except cocaine which is met in liver

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11
Q

Which are more potent, esters or amides? What determines potency?

A

Esters are more potent. Potency determind by lipid solubility

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12
Q

what properties determine onset?

A

lipid solubility and pKa

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13
Q

What is the measure of local potency for LA that is similar to MAC?

A

Cm

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14
Q

What factors determine the absorption of LA?

A

DosageSite of injectionDrug-tissue bindingLocal blood flowvasoconstrictors

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15
Q

What side effect can metabolites of prilocaine and benzocaine have?

A

methemoglobinemia (ortholuidine)

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16
Q

What is the metabolite of esters that may cause an allergic rxn?

A

para aminobenzoic acid (PABA)

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17
Q

What is the physiologic effect of methemoglobinemia?

A

decreases O2 and CO2 carrying capacity of hemoglobin

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18
Q

Which group of pts have a higher risk for methemoglobinemia?

A

neonates due to fetal hemoglobin

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19
Q

What is normal methemoglobinemia?

A

<1%

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20
Q

What are the S & S of methemoglobinemia?

A

SOBcyanosischocolatey-brown arterial blood pulse ox that always reads 85%

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21
Q

What is the treatment for methemoglobinemia?

A

1-2 mg/kg methylene blue

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22
Q

Does addition of vasoconstrictors affect onset of LA?

A

no

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23
Q

Vasoconstrictors _________ duration of LA by limiting systemic _________ and maintaining the drug concentration at the _______.

A

increasesabsorptionnerve

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24
Q

Addition of epi (increases/decreases) the chance of systemic toxicity?

A

decreases

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25
Q

What is concentration of epi used with LA?

A

1:200,000 or 5 mcg/ml

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26
Q

How much does epi prolong the effect of bupivicaine?

A

epi has very little effect with bupivicaine

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27
Q

what factors influence the possibility of absorption leading to systemic toxicity?

A

DoseVascularity of sitepresence of epiproperties of the drug

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28
Q

Subcutaneous, intravenous, sciatic, tracheal, intercostal, brachial plexus, caudal, epidural paracervical. Arrange from most to least vascular

A

intravenous>tracheal>intercostal>caudal>paracervical>epidural>brachial plexus>sciatic>subcutaneous

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29
Q

What effects does systemic toxicity have on CNS?

A

Circumoral numbnessRestlessnessslurred speech siezure

30
Q

What effects does systemic toxicity have on the cv system?

A

HypotensionDecreased cardiac conductionVentricular arrythmias

31
Q

Which has worse effects on the CV system? lidocaine or bupivicaine?

A

bupivicaine

32
Q

What is the limit for dosages for lidocaine?

A

5mg/kg/ without epi7mg/kg with epi

33
Q

What is the limit of the dose of bupivicaine?

A

2.5 mg/kg

34
Q

What is the method of action of cocaine?

A

aside from its local effect cocaine also blocks reuptake of dopamine and norepi

35
Q

How is cocaine used clinically?

A

mostly in ENT surgery for the nose due to its vasoconstrictive and local effects

36
Q

What is the peak time of intranasal cocaine?

A

30-45 minutes

37
Q

What are the adverse effects of cocaine?

A

increased HR, ventricular arrhythmias, and coronary vasoconstriction

38
Q

How do you treat the toxicity of cocaine?

A

Supportive treatmentnitroglycerine

39
Q

Is ephedrine a good choice for a chronic cocaine user?

A

No. Norepi stores will be depleted so ephedrine won’t work

40
Q

How long does lidocaine last in a spinal?

A

<1.5 hours

41
Q

What is the side effect of lidocaine in a spinal?

A

transient neurological symptoms

42
Q

What is a usual concentration of lidocaine for a spinal?

A

5% with 7.5% dextrose

43
Q

How long does bupivicaine last in a spinal?

A

2-2.5 hours

44
Q

What is a usual concentration of bupivicaine used for a spinal?

A

0.5% and 0.75% with or without dextrose

45
Q

How long does tetracaine last in a spinal?

A

2-3 hours up to 5 with epi

46
Q

What is the usual concentration of tetracaine used for a spinal?

A

1% solution, can be mixed with 10% dextrose

47
Q

When and how does epidural anesthesia during deliveray become a problem for the neonate?

A

When the baby is in distress, it will become acidotic which traps the drug. toxicity may become a problem, esp with lido

48
Q

What is the differences in volume used for epidural vs spinal?

A

Spinal usually uses 1-2 ml (up to 3-4 with bupivicaine according to the chart in the notes) while epidurals require 15-30ml

49
Q

How is the duration of a bier block determined?

A

tourniquet time

50
Q

How much 5% lidocaine or prilocaine would you use for a bier block?

A

50 cc

51
Q

Which has a lower plasma concentration in a bier block at the same dose, prilocaine or lidocaine?

A

prilocaine

52
Q

How much bupivicaine do you use for a bier block?

A

don’t use bupivicaine for a bier block, more likely to cause cardiac effects when tourniquet is deflated

53
Q

The _______ of the drug determines the amount of local anesthetic that exists in the nonionized form in the tissue

A

pKa

54
Q

Which drugs are used for topical anesthesia?

A

prilocaine,cocaine, lidocaine (w/ oxymetazoline

55
Q

What is local infiltration?

A

Extravascular placement of local anesthetic in the area to be anesthetized

56
Q

What anesthetic is in hurricane spray?

A

benzocaine

57
Q

Name a procedure where nebulized lidocaine may be used?

A

awake bronchoscopy

58
Q

What is emla?

A

eutectic mixture of local anesthetic (a cream that is put on the skin and held there with a tegaderm)

59
Q

What is the impediment that makes it difficult for local anesthesia to cross skin

A

keratin in the skin

60
Q

How long is the onset and duration of emla?

A

1 hour, duration ~ 2 hrs

61
Q

What is the dose for emla?

A

1-2 gram/10cm2 area of skin

62
Q

Which patient is contraindicated for emla?

A

<1mo

63
Q

Can a patient use an emla if they are susceptible to methemoglobin?

A

yes, just don’t use prilocaine or benzocaine in the preparation

64
Q

How much EMLA do you use for broken skin?

A

Don’t use on broken skin

65
Q

Which drugs are considered short acting for infiltration anesthesia?

A

procaine-20-30 minChloroprocaine 15-30 min

66
Q

Which drugs are considered moderate duration for infiltration anesthesia?

A

Lidocaine-30-60 minMepivacaine 45-90 minprilocaine 30-90

67
Q

Which drugs are long acting for infiltration anesthesia?

A

Bupivacaine 120-240 minEndocaine 120-180 min

68
Q

What are the first 4 symptoms of local anesthetic toxicity?

A

circumoral numbnesstinnitiuslightheadednessvisual disturbances

69
Q

What are the last 5 symptoms of LA toxicity?

A

Muscle twitchingUnconsciousnessconvulsionsRespiratory depressioncardiovascular collapse

Anes. Pharm. Me (15 decks)

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