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6903 - Special Populations > PNB - General > Flashcards

PNB - General Flashcards

1
Q

peripheral nerve blood flow is regulated by?

A

sympathetic nervous system

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2
Q

what is the epineurium?

A
  • enveloping external connective sheath

- contains many nerve fascicles

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3
Q

what is contained in a nerve fascicle?

A

-nerve fibers and capillaries in loose connective tissue

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4
Q

what is the perineurium?

A

-multi-layered epithelial sheath that surrounds the individual nerve fascicles

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5
Q

what type of junctions does the nerve capillary endothelium have?

A
  • tight junctions

* similar to BBB

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6
Q

should you perform nerve blocks in patients that are sedated or under general anesthesia?

A

-no: cannot tell you if they are having pain on injection

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7
Q

nerve blocks - mechanism of injury

A
  • mechanical: needle trauma, intraneuronal injection
  • neuronal ischemia
  • neurotoxicity of local anesthetics
  • drug error
  • infection
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8
Q

strategies to avoid mechanical injury

A
  • use short beveled needle
  • avoid high pressure injections
  • avoid fast injections
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9
Q

the ‘perfect storm’ of neuronal ischemia

A
  • endoneural injection
  • epinephrine-containing local anesthetics
  • prolonged tourniquet times
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10
Q

what is the best probe size for PNB?

A

25L

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11
Q

acoustic impedance

A
  • measure of how the ultrasound transverses the tissue

- depends on the density of the medium and velocity of the ultrasound through the medium

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12
Q

acoustic impedance mismatch

A
  • large difference in acoustic impedance

- the larger the mismatch, the more is reflected and less is transmitted

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13
Q

tissue attenuation

A
  • loss of ultrasound as a medium is transversed
  • due to absorption of ultrasound energy
  • increases as distance from probe increases
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14
Q

what is a wavelength? what does a wavelength tell us?

A
  • the distance between two areas of maximal compression (peak of wave)
  • wavelength is proportional to penetration of ultrasound
  • image resolution is no more than 1-2 wavelengths
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15
Q

what is frequency? high versus low frequency?

A
  • the number of wavelengths that pass per unit of time

- higher frequency = clearer image, lower penetration

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16
Q

hypo-echoic

A
  • reflect little amount of sound, absorb wave
  • appear dark
  • blood vessels
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17
Q

hyper-echoic

A
  • reflect large amounts of sound, do not absorb wave
  • appear bright
  • bone, air
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18
Q

in-plane

A
  • longitudinal view of entire length of probe

* best view

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19
Q

out-of-plane

A

-perpendicular to probe

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20
Q

which view is better, in plane or out of plane?

A

-in plane

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21
Q

short axis

A

-cross section of a structure

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22
Q

long axis

A

-longitudinal view of length of structure

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23
Q

where is the interscalene block completed?

A

-at the level of the roots of the brachial plexus

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24
Q

nerve anatomy levels

A
  • roots
  • trunks
  • divisions
  • cords
  • terminal nerves
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25
the brachial plexus is what roots?
-C5-T1
26
what do the brachial plexus roots pass through when coming off the spinal cord?
- posterior fascia of anterior scalene | - anterior fascia of middle scalene
27
where is the supraclavicular block completed?
-at the level of the divisions of the brachial plexus
28
trunks of the brachial plexus
- upper = C5-C6 - middle = C7 - lower = C8-T1
29
where do the trunks of the branchial plexus travel through?
- between anterior scalene and middle scalene - subclavian artery lies anterior to nerve bundle - pass behind the first rib and divide into divisions
30
brachial plexus divisions
- each trunk divides into an anterior and posterior division | - superior and posterior to the subclavian artery
31
where is the infraclavicular block completed?
-at the level of the cords of the brachial plexus
32
brachial plexus cords
- three cords branch from divisions at the level of the coracoid process - lateral, medial, posterior cords
33
brachial plexus cords: lateral
- combines with a branch from median cord to form median nerve - musculocutaneous nerve - located in coracobrachialis muscle
34
brachial plexus cords: medial
- combines with a branch from lateral cord to form median nerve - ulnar nerve - located in subcutaneous tissues
35
brachial plexus cords: posterior
- radial nerve | - axillary nerve branches early
36
brachial plexus terminal nerves
- vary with anatomy | - remain close to axillary artery
37
brachial plexus terminal nerves: radial
-posterior to axillary artery
38
brachial plexus terminal nerves: median
-superior to axillary artery
39
brachial plexus terminal nerves: ulnar
-inferior to axillary artery
40
where is the axillary block completed?
-at the level of the terminal nerves of the brachial plexus
41
what nerve is consistently missed in an axillary block? why?
- musculocutaneous nerve | - its branches from the terminal branches early
42
interscalene block - site blocked
-most reliable for C5-C7 -not reliable for C8-T1 (ulnar side) -sensory anesthesia to cervical plexus (C2-C4) -shoulder and upper arm surgery *caution for phrenic nerve paralysis (affects by volume injected)
43
interscalene block - approach
- supine with head turned away - landmarks: cricoid cartilage, lateral border of sternocleidomastoid muscle, interscalene groove - always aim needle caudal and lateral
44
supraclavicular block - site blocked
- forearm and hand, below mid-humerus level - nerves are tightly packed = onset is fast and deep * risk of pneumothorax * 20 mL to avoid phrenic nerve paralysis (60%)
45
supraclavicular block - approach
- arm at side - palpate clavicle and scalene muscles - place probe at midpoint of clavicle to locate subclavian artery - plexus is located superior and posterior to subclavian artery
46
infraclavicular block - site blocked
- below the mid-humerus - musculocutaneous nerve may need separate injection because it can diverge higher - longer onset
47
infraclavicular block - approach
- supine with head turned away - place probe interior to clavicle and medial to the coracoid - visualize axillary artery deep in pectoralis - cords surround it * always advance needle posterior and caudal to avoid pneumothorax
48
axillary block - nerves missed
- musculocutaneous - medial-brachial cutaneous - medial ante-brachial cutaneous
49
axillary block - site blocked
- hand surgeries | - multiple injections because of separation of terminal nerves
50
axillary block - approach
- supine with arm abducted 90 degrees and flexed at elbow | - identify axillary artery
51
axillary block - non-ultrasound approaches
- perivascular: advance needle close to artery while aspirating, withdraw and insert 3-4 mL, repeat twice and then complete on opposite side - trans-arterial approach: insert through vessel, inject 10 mL when there is no longer blood return, pull needle back through artery, inject 10 mL where there is no longer blood return
52
mid-humeral approach: median
- place PNS next to brachial artery on superior side in direction of axilla - flexion of wrist/fingers, pronation of forearm
53
mid-humeral approach: ulnar
- redirect needle posterior and inferior from brachial artery - flexion of wrist/ring finger + pinky, adduction of thumb
54
mid-humeral approach: radial
- close to ulnar | - extension of wrist/fingers
55
mid-humeral approach: musculocutaneous
- redirect needle superior to artery in coracobrachialis muscle - flexion of elbow
56
Horner's syndrome is associated with which block? what are the symptoms
- interscalene | - ptosis, miosis, anhydrosis
57
evaluation of brachial plexus block
- push: radial - pull: musculocutaneous - pinch: lateral = ulnar - pinch: medial = median
58
femoral nerve block -approach
- supine with leg neutral - mark inguinal crease - lateral to femoral artery, superior to iliopsoas muscle * done out of plane
59
intercostal nerve block - anatomy
- VAN: vein, artery, nerve - thoracic nerve divided into ventral (intercostal nerves) and dorsal (posterior sensation to skin, muscles, and bones of back)
60
intercostal nerve block - considerations
- need to block above and below site because of crossover of intercostal nerves - good for analgesia, not anesthesia - local anesthetics are rapidly absorbed from intercostal space - blocks above T7 are difficult
61
intercostal nerve block - approach
- angle of the rib=6-8 cm lateral from spinous process - angle needle 20 degrees cephalad and advance until you hit the rib - readjust needle caudal, and repeat until you do not hit the rib - advance a few mm until you feel a pop when entering the neurovascular bundle - aspirate and inject 3-4 mL
62
which nerves are blocked more easily?
small myelinated nerves
63
potency of LA is determined by?
lipid solubility
64
duration of LA is determined by?
protein binding
65
onset of LA is determined by?
pKa
66
nerve blocked by local anesthetics, in order of being blocked
c: pain (dull, pressure), temperature B: autonomics A delta: pain (sharp), touch
67
what nerve innervates the posterior thigh?
-posterior femoral cutaneous nerve (S1-3)

6903 - Special Populations (16 decks)

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