11. Regional Anesthesia and Epidurals Flashcards

1
Q

what stage of the pain pathway does regional anesthesia block?

A

transmission

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2
Q

why use regional anesthesia?

A

reduces amount of drugs needed and thus their side effects post before and after anesthesia

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3
Q

topical or surface anesthesia?

A
  1. larynx to avoid spasm during intubation
  2. splash block (open wound, or before closing)
  3. corneal (for eye exam, proparacaine, don’t use regular lidocaine, its acid)
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4
Q

EMLA cream

A
  • type of topical anesthetic for venipucture or small mass removal
  • long onset of action, and only lasts 30 minutes
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5
Q

Line block

A
  • local anesthetic over incision line, some surgeons don’t like the swelling it causes
  • desensitizes linea alba
  • used for c-sections to avoid opiods
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6
Q

local infiltration

A

infection of local anesthetic into or around planned surgical field, NOT A SPECIFIC NERVE

  • line block
  • intratesticular block for castration
  • ring block (extremity, tail, dehorning) HUGE volume of anesthetic
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7
Q

Epidural anesthesia target?

A

spinal nerves before exiting

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8
Q

limits of the epidural space?

vs. spinal anesthesia?

A
  • **interarcuate ligament and dura mater

vs. spinal anesthesia is in subarachnoid space (in CSF)

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9
Q

lumbo sacral space used in small animals why?

A

spinal cord ends before then, no risk of hitting it, only would hit dural sac (end of subarachnoid space, its small, but possible to hit)

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10
Q

landmarks for epidural?

A
  1. iliac crest
  2. medial sacral crest (spinal process of sacrum)
  3. spinous process of L7
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11
Q

You don’t feel most of the structures the epidural needle pierces (supraspinous ligament,interspinous ligament) but you can feel piercing the _______

A

interarcuate ligament (the roof of the epidural space)

some say ‘2 pops’ = interspinous and interarcuate ligaments

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12
Q

tuohy needle is curved to ?

A

push the dura down instead of piercing it, can feel each tissue as you pierce it

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13
Q

hanging drop technique

A

advance needle until percieved interarcuate ligament. fill hub of needle with saline. when needle enters epidural space the drop should be* aspirated!! Can be a false negative.

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14
Q

Loss of resistance technique

A
  • advance needle, attach syringe, apply pressure to plunger and advance needle thru interarcuate ligament.
  • RESISTANCE DROPS suddenly in epidural space
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15
Q

drugs in epidural?

A
  1. local anesthetic
    - low concentration bupivicaine can cause sensory block without motor blockade
  2. opioids
    - morphine, fentanyl
    - analgesia without motor blockade
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16
Q

What amount of animal is desensitized?

A

depends on volume being injected into epidural space. more volume -> higher up towards thorax (all the way up could cause respiratory paralysis)

17
Q

advantage of peripheral nerve block?

A

small amount of anesthetic will block a huge area.

18
Q

inject anesthetic into the nerve?

A

NOOO will cause irreparable nerve damage

19
Q

techniques for peripheral nerve blocks?

A
  1. blind
  2. nerve stimulation (using insulated needle, based on muscular response) only works for SENSORY AND MOTOR nerves
  3. ultrasound guidance
20
Q

current needed to cause muscle response?

A

0.3-0.5 mA

lower than 0.3 may mean needle is IN THE NERVE

21
Q

positive electrode is connected to the ___

A

skin of the patient

22
Q

only the _____ conducts electricity

A

tip of the needle

23
Q

when injecting anesthetic, what is special about the syringe

A

want some air in the syringe with the anesthetic. Watching the air bubble deform during injection can mean the needle is in the wrong position.

24
Q

gold standard of peripheral blocks

A

ultrasound guidance, can watch anesthetic being injected around the nerve.
can be combined with stimulation

25
Q

____ frequency transducer for ultrasound guided block

A

high, better detail

26
Q

infraorbital nerve block used for?

cautions?

A

for rhinoscopy, extracting incisor/canine, nasal surgery

  • inject outside foramen, can be intra or extra-orally
  • be careful of infraorbital artery and piercing eye in cats
27
Q

maxillary nerve block
technique?
used for

A
  • thru infraorbital canal, thread IV catheter in canal then inject
  • dental procedures
28
Q

inferior alveolar/mandibular block

vs. mental block

A
  • entire lower jaw
  • palpade mandibular foramen or do extraoral by palpating foramen with finger

just lower incisors

29
Q

complication with bilateral inferior alveolar block

A

spread and block lingual -> self mutilation

30
Q

intercostal block
anatomy?
technique?
use?

A
  • nerve on caudal margin of rib
  • blind, touch rib, then pull back more caudally, aspirate
  • if incising at 4th space block that rib and 2 in front and behind.
31
Q

Can you do a subarachnoid injection (spinal injection/ into CSF) at the lumbosacral space?

A

yes so be careful, especially in young animals

32
Q

Difference between spinal (subarachnoid) vs. epidural

A
  • ## spinal injection is faster, needs less volume, very dense homogenous bilateral block, stays in CSF doesn’t last as long
33
Q

most common tissue in epidural space?

so?

A

fat

effect is not as predictable, homogenous, ‘patchy’

34
Q

only in the lumbosacral space?

A

nah, can do in thoracic area to block thoracic limb nerve roots (using nerve stimulation) But be careful of the brainstem

35
Q

drugs for local anesthetics

A
  • bupivicaine - .5-1 mg/kg 1-2 hours of surgery, 4-6 of analgesia
  • ropivacaine - less toxic, same duration, some vasoconstrictive effect
  • lidocaine - short acting .5-1hr
36
Q

how to know the local anesthetic epidural has spread

A
  1. sympathetic trunk -> relaxation of respiratory muscles.
  2. bradycardia

if it hits the respiratory center that really bad

37
Q

higher concentration anesthetic of epidural

A

better block, longer lasting, faster onset

38
Q

ideal drug for epidural space?

why?

A

**morphine

low liposolubility!!!!

39
Q

drugs used in epidurals?

A
  1. opioids
  2. Alpha 2s (good analgesia, some local anesthetic effect, bradycardia)
  3. Ketamine (short analgesia, can prolong local anesthetics, not useful alone)
  4. vasoconstrictors/epinephrine (may prolong duration of action, more effective with lidocaine/drugs causing severe vasodilation)