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Pharm 2 > Quiz 5 > Flashcards

Quiz 5 Flashcards

1
Q

What are the 3 layers of peripheral nerves?

A

endoneurium (inside), perineurium (middle), epineurium (outside)

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2
Q

Where are the Na gated channels located on peripheral nerves?

A

on the Nodes of Ranvier (break points between successive bands of myelin)

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3
Q

What do the Schwann cells do?

A

cell support and insulation- make myelin

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4
Q

What is saltatory conduction and where does it NOT occur?

A

AP jump from node to node- does not happen in C fibers because no myelination

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5
Q

What is the normal RMP?

A

-70 to -90 mV

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6
Q

What is the MoA for LA?

A

drug reversibly binds to sodium channel in the nerve in the INACTIVATED state and prevents them from opening

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7
Q

How many successive nodes of Ranvier must the LA bind to for it to be effective?

A

3

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8
Q

The ? form has to diffuse into the nerve axon first, and once inside, the new equilibrium forms between ionized and nonionized forms. The ? form binds to receptors

A

non-ionized, ionized

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9
Q

Do LA have an effect on RMP or threshold?

A

no

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10
Q

Describe A alpha fibers

A

motor efferent, proprioception; 12-30 mm diameter, 70-120 m/s conduction, heavily myelinated

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11
Q

Describe A beta fibers

A

touch and pressure, 5-12 mm diameter, 30-70 m/s conduction, myelinated

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12
Q

Describe A gamma fibers

A

motor efferent, 3-6 mm diameter, 30-70 m/s conduction, myelinated

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13
Q

Describe A delta fibers

A

pain, temp and touch; 2-5 mm diameter, 12-30 m/s conduction, myelinated

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14
Q

Describe B fibers

A

preganglionic autonomic fibers; <3 mm diameter, 3-14 m/s conduction, some myelination

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15
Q

Describe C dorsal root fibers

A

pain and temperature, 0.4-1.2 mm diameter, 0.5-2 m/s conduction, not myelinated

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16
Q

Describe C sympathetic fibers

A

postganglionic sympathetic fibers, 0.3-1.3 mm diameter, 0.7-2.3 m/s conduction, not myelinated

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17
Q

What fibers make up motor and muscle control?

A

A alpha fibers

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18
Q

What fibers make up sensory fibers and control touch, vibration, position, perception?

A

A alpha and beta

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19
Q

What fibers make up sensory fibers and control cold perception, and pain?

A

A delta fibers

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20
Q

What is the order in which nerves are blocked?

A

1) autonomic 2) sensory 3) motor

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21
Q

What is the minimum blocking concentration (Cm)?

A

lowest concentration of drug that is needed for blocking impulse propagation

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22
Q

The Cm of motor fibers is about ? that of sensory fibers

A

twice

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23
Q

What factors can affect the Cm of LA?

A

temp, pH, calcium concentration of bathing solution

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24
Q

Almost all LA are ?, which exist in both ? and ? forms when injected into physiological pH (there is an exception)

A

tertiary amines; ionized and nonionized (benzocaine is an exception- secondary amine, permanently non-ionized)

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25
Q

What parts of the LA molecule make them lipophilic and hydrophilic?

A

aromatic ring- lipophilic

amine- hydrophilic

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26
Q

Which type of LA have a higher allergic potential?

A

esters- broken down to PABA

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27
Q

What will increase LA potency, and how can this become a problem?

A

a higher lipid solubility- also correlated with higher protein binding, longer DoA, and higher tendency for cardiotoxicity

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28
Q

What is the most lipid soluble ester of commonly used LA?

A

tetracaine

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29
Q

What is the most lipid soluble amide?

A

bupivacaine

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30
Q

What is more important in terms of DoA, protein binding or lipid solubility?

A

protein binding

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31
Q

What is the most important factor for onset?

A

ionization (lipid solubility)

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32
Q

LA are weak ? and prefer to bind to ?

A

bases; alpha 1 acid glycoprotein

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33
Q

Do esters or amides have shorter DoA?

A

esters

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34
Q

List the LA from most to least in terms of protein binding

A

bupivicaine (95%) > etidocaine, ropivicaine, tetracaine (94%) > mepivicaine (77%) > lidocaine (64%) > procaine (6%) > chloroprocaine (0%)

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35
Q

What does the addition of sodium bicarb to LA do?

A

increases pH of the LA, and therefore increases the amount of drug in the nonionized form

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36
Q

What LA are considered low potency and short DoA (60-90 min)?

A

procaine and chloroprocaine

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37
Q

What LA are considered inermediate potency and duration (90-240 min)?

A

mepivacaine, prilocaine, lidocaine

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38
Q

What LA are considered high potency, long DoA (180-600 min)

A

tetracaine, bupivacaine, etidocaine, ropivacaine, levobupivacaine

39
Q

What is the max single dose for infiltation of procaine?

A

500-600 mg or 7 mg/kg

40
Q

What is the max single dose for infiltration of chloroprocaine?

A

600-800 mg or 11 mg/kg

41
Q

What is the max single dose for infiltration of tetracaine?

A

100 mg (topical)

42
Q

What is the max single dose for lidocaine?

A

300 mg 4.5 mg/kg

43
Q

What is the max single dose for prilocaine?

A

400-600 mg or 8 mg/kg

44
Q

What is the max single dose for mepivacaine

A

300-400 mg or 7 mg/kg

45
Q

What is the max single dose for bupivacaine and levobupivacaine?

A

175 mg or 2.5 mg/kg

46
Q

What is the max single dose for ropivacaine

A

200-250 mg or 3 mg/kg

47
Q

What is the pKa of procaine?

A

8.9

48
Q

What is the pKa of chloroprocaine?

A

8.7

49
Q

What is the pKa of tetracaine?

A

8.5

50
Q

What is the pKa of lidocaine and prilocaine?

A

7.9

51
Q

What is the pKa of mepivacaine?

A

7.6

52
Q

What is the pKa of bupivacaine, levobupivacaine, and ropivacaine?

A

8.1

53
Q

List from most absorbent to least absorbent injection sites

A

IV> tracheal > intercostal > caudal > paracervical > epidural > brachial plexus > subarachnoid, sciatic, fem > subcutaneous

54
Q

What is the mnemonic for injection sites?

A

In Time I Can Please Everyone But Susie & Sally

55
Q

What does the addition of epi do for LA?

A

decreases rate of absorption, facilitates neuronal uptake, enhances analgesic quality, prolongs DoA, limits toxic SE

56
Q

What is the max dose of epi you can administer to prolong LA?

A

200-250 mcg or 3-5 mcg/kg

57
Q

What concentration of epi should you use for LA?

A

1:200,000 (5 mcg/mL)

58
Q

What are some contraindications to epinephrine?

A

unstable angina, cardiac dysrhythmias, uncontrolled HTN, uteroplacental insufficiency, areas that block collateral BF (digits)

59
Q

What has the most significant vasoconstrictive property?

A

cocaine

60
Q

What topical LA do we use, what is it made with, and how long does it last?

A

EMLA cream; 1:1 lidocaine and prilocaine, lasts 1-2 hours

61
Q

When is EMLA cream contraindicated?

A

open skin, mucous membranes, amide LA allergy

62
Q

How are amides metabolized?

A

P450 enzymes in the liver

63
Q

What can the metabolites of prilocaine and benzocaine do?

A

can accumulate after large doses and convert hemoglobin to methemoglobin- treat with methylene blue

64
Q

How are esters metabolized?

A

plasma cholinesterases- rapid hydrolysis

65
Q

What are the 4 conditions that increase duration of esters because they decrease cholinesterase activity?

A

pregnancy, liver disease, 1st 6 months of life, atypical plasma cholinesterase

66
Q

What are 4 drugs that prolong ester activity by decreasing plasma cholinesterase activity?

A

echthiophate, neostigmine, pyridostigmine, edrophonium

67
Q

What is the least toxic amide?

A

prilocaine

68
Q

Which amide has the slowest hepatic metabolism?

A

bupivacaine

69
Q

What are the 3 least potent amides?

A

lidocaine, mepivicaine, prilocaine

70
Q

What is LAST?

A

local anesthetic systemic toxicity

71
Q

What can LAST cause?

A

seizures, coma, blockade of cardiac ion channels, respiratory and cardiac arrest, muscle twitching

72
Q

What are the most common anesthetics that can lead to LAST?

A

epidural, axilary, interscalene

73
Q

What is the most common drug that causes LAST?

A

bupivicaine, due to its high affinity for Na channels

74
Q

What are predisposing risk factors for LAST?

A

pregnancy, hypoxemia, respiratory acidosis

75
Q

What are some early signs of LAST?

A

perioral numbness, facial tingling, tinnitis, metallic taste, slurred speech, vertigo

76
Q

What is a safe plasma concentration of lidocaine

A

1-5 mcg/mL

77
Q

What plasma level of lidocaine leads to cardiovascular collapse?

A

> 25 mcg/mL

78
Q

What is the treatment for LAST?

A

airway support, mechanical compressions, 20% lipid solution, cardiac bypass

79
Q

What is the least toxic ester?

A

chloroprocaine

80
Q

What is the most toxic ester?

A

tetracaine

81
Q

Who should you avoid esters in?

A

patients with atypical or depressed cholinesterase activity

82
Q

Never administer a LA into a neuraxial compartment if…

A

it contains a preservative

83
Q

What drugs decrease hepatic BF and decrease lidocaine clearance?

A

propranolol (BB) and cimetidine (H2 blockers)

84
Q

What is the max dose of bupivicaine with epi?

A

225 mg

85
Q

What is the max dose of lidocaine with epi?

A

7 mg/kg or 500 mg

86
Q

What is the max dose of mepivacaine with epi?

A

500 mg

87
Q

What is the max dose of benzocaine, with or without epi?

A

200 mg

88
Q

What is the max dose of chloroprocaine with epi?

A

1000 mg or 14 mg/kg

89
Q

What is the max dose of cocaine?

A

3 mg/kg or 150 mg

90
Q

LA’s typically work by binding to the receptor in the Na channel within the neuron while in their charged form. Which LA is an exception to this rule?

A

benzocaine (weak acid)

91
Q

LA with which pKa value would you expect to have the quickest onset of action?

A

7.4

92
Q

LA produce a differential blockade in which different modes of nerve transmission are interrupted in an equal fashion. Which is the correct order?

A

temp sensation, sharp pain, light touch

93
Q

The concept of Cm is most similar to?

A

MAC

Pharm 2 (7 decks)

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