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My Rachel Cards > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

1
Q

What was the first LA?

A

Cocaine 1884

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2
Q

First ester LA?

A

Procaine 1905

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3
Q

First amide LA?

A

Lidocaine 1843

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4
Q

Describe the chemical structure of LAs?

A

Lipophilic and hydrophilic portion separated by hyrdrocarbon

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5
Q

Benzene ring is made of the lipophilic or hydrophilic portion?

A

Lipophilic portion

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6
Q

The hydrophilic portion of the LA is also called ______?

A

Quaternary amine

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7
Q

What are the only two pure isomer LA?

A

Ropivacaine and Levobupivacaine

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8
Q

Are ropivacaine and levobupivacaine left or right pure isomers?

A

Pure Left isomers

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9
Q

What is the benefit of an S-entantiomer LA?

A

Less neuro and cardio toxic

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10
Q

What is the mechanism of action of LA?

A

Inhibit Na+ ions passage through ion selective Na+ channels

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11
Q

What are the effects of LA on rate of depolarization, threshold potential, resting membrane potential and action potential?

A
  1. Slows rate of depolarization
  2. Stops an action potential
  3. Does not alter resting membrane potential or threshold potential
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12
Q

Does the LA bind to the internal or external part of the Na+ channel?

A

Internal

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13
Q

Why do nerves with more activity have a faster blockade?

A

Access to receptor is only possible during activated open state.
More frequent firing= more opportunity for access

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14
Q

What is Cm?

A

Minimum concentration to produce conduction blockade

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15
Q

Name one factor than increases Cm?

A

Larger diameter nerve

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16
Q

Name two factors that decrease Cm?

A
  1. Higher frequency

2. Higher pH

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17
Q

How many Nodes of Ranvier must be blocked?

A

2, preferably 3

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18
Q

T/F: Cm for sensory is about twice motor?

A

False; Cm for motor is about twice sensory

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19
Q

Order of nerve blockade for spinal or epidural anesthesia?

A
  1. B fibers
  2. C and A Delta
  3. A Gamma
  4. A Beta
  5. A Alpha
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20
Q

Which fibers are preganglionic sympathetic efferent?

A

B Fibers (Efferent=exiting the brain)

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21
Q

What are examples of C and A Delta Fibers?

A

C: Pain, temp, touch afferent (Afferent=arriving to the brain)
A Delta: Post ganglionic sympathetic neurons

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22
Q

Mneumonic for Order of blockade:

A

ATP-TP-MVP

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23
Q

ATP-TP-MVP

A
  1. Autonomc
  2. Temperature
  3. Pain
  4. Touch
  5. Pressure
  6. Motor
  7. Vibration
  8. Proprioception
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24
Q

According to Nagelhout, what is the order of nerve blockade?

A
  1. Autonomic
  2. Superficial pain, touch, temp
  3. Motor function
  4. Proprioception
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25
Q

All LA are weak bases except which one?

A

Benzocaine
Weak acid
pKa= 3.5

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26
Q

What form must LA be in to cross lipid bilayer?

A

un-ionized

27
Q

T/F: As you decrease pH, you become more and more unionized?

A

False; As you decrease pH, you become more and more ionized

28
Q

What does adding HCO3 do to LA?

A

Higher pH is closer to pKa=more un-ionized=faster onset by 3-5mins=lessens sting of local infiltration

29
Q

What LA quality is related to potency?

A

Lipid solubility

30
Q

What LA quality is related to onset?

A

State of ionization

31
Q

What LA quality is related to duration of action?

A

Protein binding

32
Q

How are amides metabolized and cleared?

A

Hepatic metabolism.

Minimal renal excretion of unchanged drug

33
Q

What is the fastest acting amide LA?

A

Prilocaine

34
Q

Name two intermediate acting amide LAs?

A
  1. Lidocaine

2. Mepivicaine

35
Q

Name three slow acting amide LAs?

A
  1. Etidocaine
  2. Bupivacaine
  3. Ropivacaine
36
Q

Name a rapid, intermediate and slow acting ester LAs?

A

Rapid=Chlroprocaine
Intermediate=Procaine
Slow=Tetracaine

37
Q

Where are esters metabolized?

A

Rapid hydrolysis by cholinesterases in the plasma

38
Q

Which ester LA is the one exception to hydrolysis?

A

Cocaine

39
Q

Which type of LA has PABA as a metabolite?

A

Esters

40
Q

Which common local injection site contains little to no cholinesterase enzyme?

A

CSF- must wait until drug goes into systemic circulation for hydrolysis

41
Q

What 5 situations inhibit plasma cholinesterase?

A
  1. Primary deficiency
  2. Liver disease
  3. Increased BUN
  4. Parturients
  5. Chemotherapy patients
42
Q

Which vasoconstrictor has been found to be superior as an additive to LA?

A

Epinephrine

43
Q

Which 2 LAs have no vasodilator activity?

A

Cocaine (significant vasoconstriction) and Ropivacine (parenteral vasoconstrictive)

44
Q

Dose for clonidine additive to neuraxial anesthesia?

A

Epidural 150mcg or 2mcg/kg

Spinal 45mcg

45
Q

When mixing different LAs, is there an additive or synergistic effect?

A

Additive

46
Q

What are S&S of a real LA allergic reaction?

A
  1. Rash
  2. Urticaria
  3. Laryngeal edema
  4. HoTN
  5. Bronchospasm
47
Q

Max dose of plain bupivacaine vs with epi?

A

Plain: 175mg or 2.5mg/kg
Epi: 225mg or 3mg/kg

48
Q

Max dose plain lidocaine vs with epi?

A

Plain: 300mg or 4.5mg/kg
Epi: 500mg or 7mg/kg

49
Q

Max dose plain ropivacaine vs with epi?

A

Both: 200mg or 2.5mg/kg

50
Q

What is the progression of CNS effects from LA toxicity called?

A

Hadzic’s Progression

51
Q

List Hadzic’s Progression:

A
  1. Vertigo
  2. Tinnitus
  3. Ominous feelings
  4. Circumoral numbness
  5. Garrulousness
  6. Tremors
  7. Myoclonic jerks
  8. Convulsions
  9. Coma
  10. CV Collapse
52
Q

Above what plasma concentration dose lidocaine begin Hadzic’s progression?

A

> 5mcg/ml

53
Q

What is responsible for the speed of systemic levels of LA?

A

Blood flow of tissues

54
Q

Mneumonic for fastest to slowest bloow flow of tissues in relation to LA distribution

A

In Time I Can Please Everyone But Suzi and Sally

55
Q

In Time I Can Please Everyone But Suzi and Sally

A 
IV
Tracheal
Intercostal
Caudal
Paracervical
Epidural
Brachial Plexus
Subarachnoid
Subcutaneous
56
Q

What is typically S&S of TNS?

A

Moderate to severe pain in lower back, buttocks, and posterior thighs

57
Q

What is administration type/area carries highest risk of TNS?

A

Intrathecal lidocaine

58
Q

What two things are a contraindication for neuraxial anesthesia as they are indicative of risk for Cauda Equina Syndrome

A

Sacral dimple or hairy nevus

59
Q

What is more likely to happen at moderate LA toxicity levels, CNS or CV symptoms?

A

CNS. CV toxicity requires 3 times blood concentration than seizure threshold

60
Q

Which particular LA might you see CV symptoms prior to CNS?

A

Bupivacaine

61
Q

What is dose for Lipid Emulsion therapy?

A

1.5ml/kg Lean body weight over 1 min followed by 0.25ml/kg/min gtt

62
Q

What is treatment for methemoglobinemia?

A

Methylene blue 1-2mg/kg over 5 mins

63
Q

Which LAs are high risk for methemoglobinemia?

A
  1. Prilocaine
  2. Benzocaine
  3. Cetacaine
  4. Lidocaine

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