5: Local Anesthetics - Smith Flashcards

1
Q

define local anesthetic

A
  • block n conduction when applied locally to n tissue in appropriate concentrations and act on any part of nervous system and on every type of n fiber
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2
Q

have two “I”s in chemical name

A

amides

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3
Q

where are amides and esters metabolized?

A

amides - liver (i)

esters - in bloody by pseudocholinesterase

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4
Q

MOA anesthetics

A
  • inhibit excitation (generation) and conduction of n impulse by increasing the threshold for depolarization
  • cell membrane
  • prevents increase in permeability of membranes to Na+ (sodium channels)
  • can act on K+ channels
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5
Q

which n fibers are more sensitive to anesthetic?

A

small and unmyelinated

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6
Q

order of function

A
pain
temp
touch
propioception
deep pressure
movement
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7
Q

increasing pH will ______ effectiveness of anesthetic

A

decrease

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8
Q

why use epinephrine with local anesthetic?

A
  • increases duration of action
  • decreases systemic toxicity
  • provides hemostasis
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9
Q

where should epinephrine not be used?

A

ears
nose
penis
toes/fingers

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10
Q

concentration of epi

A

1:100,000 - safer at 1:200,000

dilute to 1:200,000 by (ex) drawing 5 cc of epi and lidocaine and 5 cc lidocaine

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11
Q
\_\_ % contains \_\_mg/ml or cc
0.25%
0.50%
1%
2%
A

2.5 mg/ml or cc
5
10
20

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12
Q

10 cc of 1% lidocaine contains _____ mg

A

100 mg

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13
Q

how many mg of drug in …

  • 15cc of 2% lidocaine
  • 15cc of 0.50% marcaine
  • 10cc of 0.25% marcaine
  • 10cc of 50/50 mix 2% lidocaine and 0.50% marcaine
A
  • 300
  • 75
  • 25
  • 100 lido, 25 marc
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14
Q

toxic dose lidocaine

A

4.5 mg/kg
= 300mg plain
= 500 mg w/ epi

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15
Q

toxic dose marcaine

A

2.5 mg/kgk
= 175 mg plain
= 225 mg w/ epi

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16
Q

how many cc of 2% lidocaine plain can be given before toxic dose reached?

A

15cc

17
Q

how many cc of 0.50% marcaine plain cna be give before toxic dose reached?

A

35 cc

18
Q

Lidocaine/xylocaine
onset =
DOA =
risk =

A

3- 5 min
3-4 hr
- vfib, cardiac arrest

19
Q

bupivacaine/marcaine/sensorcaine
onset =
DOA =

A

5-10 min
6-8 hr

  • often mixed with lidocaine to increase DOA and prolong anesthesia
20
Q

what could you add to make an injection less painful?

A
  • topical refrigerant (ethyl chloride)
  • sodium bicarb (buffer solution)
  • also use right syringe and smallest needle
  • warm the anesthetic
21
Q

injection technique

A
  • antiseptic
  • needle inserted and wheal raised
  • aspiration to prevent intravascular injection
  • needle advanced forward and anesthetic deposited
  • redirection of needle
22
Q

describe mayo block/ring block

A
  • used for bunion surgery
  • proximal first interspace and advanced plantarly
  • needle redirected medially along dorsal aspect of metatarsal
  • needle directed from dorsal to plantar on medial side of met
  • needle directed from medial to lateral on plantar side of met
  • deep peroneal n block at distal interspace

“ring block around 1st met plus one more”

23
Q

6 nerves blocked with ankle block ***

A
posterior tibial n.
saphenous n.
medial dorsal cutaneous n.
intermediate dorsal cutaneous n.
sural n.
deep peroneal n.
24
Q

5 nerves blocked with ankle block ***

A
post tibial n.
saphenous n. 
superficial peroneal n.
sural n. 
deep peroneal n.
25
Q

where do you do a post tibial n. block?

A
  • palpate pulse of post tib a and inject POSTERIOR to artery
26
Q

where do you do a saphenous n block?

A
  • lateral to great spahenous v

- anterior and lateral to medial malleolus

27
Q

where do you do a superficial peroneal n block?

A
  • lateral to EHL tendon to get medial dorsal cutaneous n

- 1 to 1.5cm anteriro to lateral malleolus for intermediate dorsal cutaneous n

28
Q

lemont’s n

A

plantarflec and invert foot to visualize n

29
Q

where do you do a sural n block?

A

1 to 1.5 cm posterior and inferior to lateral malleolus

30
Q

where do you do a deep peroneal n block?

A
  • inject b/w EDL and EHL just lateral to ant tibial a (palpate pulse)
31
Q

what is an infiltration block?

A

injection of anesthetic directly at procedure site for example, excision of wart of biopsy

32
Q

complications assoc with local anesthetics

A
  • syncope
  • allergic rxn
  • arrhythmia (PVC, lwo pulse, low oxygen, chest pain, vfib)
  • cardiac arrest