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SRNAPharmacology II > LA Review > Flashcards

LA Review Flashcards

1
Q

How do local anesthe-cs (LA) work? ••

A

LA work by preven-ng voltage-gated fast channels in the nerve axons from opening. LA bind to Na channels inside the neuron when they are in the inac-vated state.

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2
Q

• What part of the nerve cell is affected by LA? •

A

The nerve axon

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3
Q

What is the primary determinant of LA potency? •

A

Lipid solubility

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4
Q

Which LA is the standard for comparison of potency?

A

Lidocaine

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5
Q

What term defines the lowest concentra-on of LA that blocks impulse conduc-on along a give nerve fiber?

A

Minimum blocking concentration

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6
Q

What three LA are effec-ve when applied topically? 2

A

Tetracaine, lidocaine, cocaine

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7
Q

• How are nerve fibers classified?

A

Three groups of nerve fibers A, B, and C. Separated on basis of diameter. A fibers further divided into alpha, beta, gamma, and delta.

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8
Q

• Which fibers are blocked last by LA?

A

A-alpha

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9
Q

Are the largest 15-20um

A

A-alpha

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10
Q

The most myelinated, fastest conduction velocity,

A

A-Alpha

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11
Q

Responsible for motor function and proprioception.

A

A-alpha

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12
Q

The only unmyelinated fibers

A

C fibers-

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13
Q

Pain and temperature sensation.

A

Delta

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14
Q

are smallest in diameter 3-4um and provide pain and temp sensation

A

Delta fibers

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15
Q

Motor function, touch, and pressure sensation.

A

A beta and GAMMA

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16
Q

Slowest conduction

A

C fibers

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17
Q

Responsible for reflexes

A

GAMMA

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18
Q

What LA has the longest half–me elimination? • •

A

Bupivicaine

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19
Q

What 6 factors determine the absorption of a LA into surrounding vasculature and therefore influence blood levels of LA?

A

1) Total dose
2) Tissue blood flow
3) The presence of epinephrine or phenylephrine
4) Lipid solubility
5) Protein binding
6) pH

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20
Q

• The onset and extent of diffusion of a LA to its site of ac-on depends primarily on what 3 factors? •

A

1) pKa of the drug
2) Concentration
3) Lipid solubility •

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21
Q

Why does LA that is absorbed into the venous circulation initially have limited effects in systemic circula-on? •

A

Substantial uptake into lungs

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22
Q

What property of LA most determines duration of ac-on of LA? What other proper-es will determine duration of ac-on?

A

Protein binding; Lipid solubility (greater lipid solubility, the greater the dura-on of ac-on).

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23
Q

What property of LA most determines onset of ac-on of LA?

A

Ioniza-on LA with higher pKa will be more ionized that LA with lower pKa and therefore have a slower onset of ac-on. Bupivicaine (pKa of 8.1) will have a slower onset of ac-on than lidocaine (pKa 7.9)

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24
Q

Why is epinephrine added to LA solutions?

A

1) Decrease the absorption of LA and prolong the effects,
2) decrease systemic toxicity
3) permit higher doses of LA

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25
Q

What drug would you add to a LA for vasoconstriction if cardiac accelera-on is not desired?

A

Phenylephrine •

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26
Q

What is the maximum dose of epinephine when used with a LA for prolonging infiltration, brachial plexus, epidural, caudal, or intrapleural anesthesia

A

200-250mcg (3-5mcg/kg)

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27
Q

What is the optimal concentration of epinephrine in local anesthetic solutions? •

A

1:200,000 (5mcg per ml)

28
Q

How many ml of 1:100,000 epinephrine can be safely injected into adult pa-ents?

A

200-250mcg or 20-25ml of 1:100,000 ml solution (1:100,000 = 10mcg per ml)

29
Q

What LA can cause methemoglobinemia?

A

Prilocaine

30
Q

What is the only LA that produces vasoconstriction?

A

Cocaine

31
Q

What LA is an ester of Benzoic acid?

A

Cocaine

32
Q

• What is the maximum safe dose of Cocaine applied nasally or topically?

A

1.5mg/kg

33
Q

• Which amide LA is most cardiotoxic?

A

• Bupivicaine

34
Q

• Compare the frequency of hypersensitivity reac-ons with esters compared to amides?

A

Rare with esters, even rarer with amides •

35
Q

• List 4 manifestations of hypersensi-vity from LA?

A

1) Localized edema
2) urticaria
3) bronchospsasm
4) anaphylaxis

36
Q

• What are most potent and most toxic LA?

A

Tetracaine, etidocaine, and bupivacaine are equipotent. Etidocaine causes seizures at the lowest serum concentra-on among LA. Etidocaine and bupivacaine have the lowest maximum dosage ranges

37
Q

• What are the 3 most cardiotoxic LA?

A

• Bupivacaine> e-docaine> ropivacaine

38
Q

Plasma concentrations of ester LA may be elevated in patients with what problem?

A

• Deficient or atypical plasma cholinesterases • . • • • • No

39
Q

• Name 4 an-cholinesterase agents that can prolong the ac-on of ester LA? •

A

1) Echothiophate (IRREVERSIBLE) 2) neos-gmine 3) pyridos-gmine 4) edrophonium

40
Q

Name 4 condi-ons that decrease the concentra-on and hence prolong the ac-on of ester LA?

A

Pregnancy
Liver disease
1st 6 months of life
Atypical plasa cholinesterases

41
Q

When using amide LA, which drugs would you want to avoid to minimize the likelihood of cardiac toxicity? •

A

Beta-blockers
CCB’s
Digoxin, These agents decrease impulse propagation.

42
Q

What preservatives are added to LA? What are potential problems associated with their use?

A

Parabens. Allergic reactions

43
Q

Should multiuse vials be used for spinal, epidural, or intravenous regional anesthesia?

A

No

44
Q

Identify agents that potentiate amide toxicity?

A

Agents that inhibit the hepatic cytochrome p450 system or decrease hepatic blood flow (Volatile anesthetics, propranolol, cimetidine).

45
Q

• How are amides eliminated•

A

Liver metabolism •

46
Q

How are amides eliminated•

A

Liver metabolism

47
Q

Which of the amide LA is least toxic?

A

Prilocaine

48
Q

What are 3 least potent amide LA?

A

Lidocaine, mepivacaine, prilocaine

49
Q

•• What is the maximum dose of bupivacaine?

A

In general, maximum single doses of BUPIVACAINE in healthy adults should not exceed 175 milligrams without EPINEPHRINE and 225 milligrams with EPINEPHRINE 1:200,000.

50
Q

What is the maximum dose of bupivacaine?

A

In general, maximum single doses of BUPIVACAINE in healthy adults should not exceed 175 milligrams without EPINEPHRINE and 225 milligrams with EPINEPHRINE 1:200,000.

51
Q

What are ester local anesthetics?

A

Procaine, chloroprocaine, tetracaine, and cocaine • • •

52
Q

How are they eliminated?

A

Plasama cholinesterases with exception of cocaine (liver).

53
Q

Why is tetracaine the most toxic ester LA

A

Tetracaine is eliminated by plasma cholinetserases the slowest.

54
Q

What is the least potent LA

A

Procaine

55
Q

What LA is the least toxic? Why?

A

Chloroprocaine because it is eliminated faster than all other LA

56
Q

When should procaine, chloroprocaine, and tetracaine avoided?

A

In patients with atypical plasma cholinesterases and in patients with a history of allergy to an ester LA •

57
Q

Compare Bupivacaine amd Ropivacaine

A

Ropivacaine is a long acting LA similar to bupivacaine in pKa, potency and protein binding but is less cardiotoxic and produces less motor blockade.

58
Q

Why does injecting a LA with Bicarbonate increase the speed of onset?

A

The LA becomes mostly non-ionized with higher pH of surrounding solution

59
Q

Define pKa?

A

The pH at which 50% of a weak acid or weak base ionized

60
Q

LA are prepared as what kind of salts?

A

HCl

61
Q

What is the range for pKas for LA?

A

7.6 to 9.1

62
Q

What LA are most ionized at physiologic pH?

A

The LA with the highest pKas are most ionized at physiological pH ( procaine 8.9, chloroprocaine 8.7, and tetracaine 8.5)

63
Q

What LA are most un-ionized at physiological pH? •

A

The LA with the lowest pKas are the most unionized at physiological pH (mepivacaine 7.6, and e-docaine 7.7)

64
Q

The HCl salt solu-on of LA is acidified to what pH range to favor the existence of the water soluble ionized form to avoid precipita-on?

A

• pH 4.4 to 6.4

65
Q

If LA is injected into an area of local infection, will the onset of action be hastened or slowed?

A

Slowed

SRNAPharmacology II (32 decks)

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