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S5 - Regional/OB - Test 2 > Central Blocks > Flashcards

Central Blocks Flashcards

1
Q

label these guys

A
  1. epidural space
  2. ligamentum flavum
  3. cauda equina
  4. cona medullaris
  5. dura mater
  6. arachnoid mater
  7. pia mater
  8. spinal cord
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2
Q

what connects the transverse process of a vertebra to the vertebral body?

A

pedicles

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3
Q

what connects the transverse process of a vertebrae to the spinous process?

A

lamina

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4
Q

where does the spinal cord terminate in most adults?
what is this called?

A

L1/L2 (depends on who you ask)

conus medullaris

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5
Q

what does the spinal cord transition into once it ends?

A

collection of nerves called the cauda equina

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6
Q

what is the importance of the cauda equina?

A

lessened risk of direct cord injury when a needle is placed into this space

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7
Q

where is the epidural space located?

A

posterior to the dura and anterior to the ligamentum flavum

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8
Q

contraindications to a central block (5)

A
  1. infection at the site of injection or near CNS
  2. coagulopathy or use of anticoagulants
  3. neuromuscular disease
  4. cardiac frailty
  5. patient consent & ability to tolerate procedure
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9
Q

when placing an epidural, how do you know that the needle is passing through the ligamentum flavum and enters the epidural space?

A

a sudden loss of resistance to injection of air or saline

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10
Q

how do you know that your spinal is in the correct place (subarachnoid space)?

A

freely flowing CSF

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11
Q

what is the principal site of action for neuraxial blockade?

(M&M)

A

believed to be the nerve root, at least during initial onset of block

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12
Q

what is the 1st ligament encountered when inserting the needle for a central block?

A

supraspinous ligament

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13
Q

what is the most internal ligament that is immediately posterior to the epidural space?

A

ligamentum flavum

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14
Q

2 approaches to place a central block

A

midline

paramedian

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15
Q

why is the epidural considered a “potential space”?

A

it’s a collapsed structure like an uninflated balloon or esophagus

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16
Q

what is contained in the epidural space?

A

nerves, vessels, and fat where roots pass outwardly

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17
Q

if using the midline approach, how deep to the skin is the epidural space generally?

A

5 cm

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18
Q

what borders the epidural space?

A

epidural veins

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19
Q

why are central blocks contraindicated in a pt with MS?

A

effects of LA on cord

if necessary, epidural would be better than a spinal

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20
Q

cardiac diseases that are absolute contraindications for central blocks

why?

A

outflow obstructions: aortic stenosis, HOCM, IHSS

SVR specific BP regulation, sympathectomy can result in cardiac arrest with difficulty resuscitating (TC said when they die they die 4real)

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21
Q

what lab might you want to get in a pt on aspirin needing a central block?

A

TEG - tests platelet function

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22
Q

ASRA recommendations for INR level prior to neuraxial block

(article)

A

“normal”

< 1.5

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23
Q

s/s that warrant immediate evaluation after central block

A
  • altered pain, temp, or motor function
  • changes in bowel or bladder function
  • severe back pain
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24
Q

what is a “total” spinal?

A

injected meds block nerves high into the thoracic or even cervical levels

results in SNS blockade → bradycardia, hypotension, vascular collapse, apnea, LOC

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25
Q

interventions you should expect to do after you realized you just gave your pt a total spinal (oopsies)

A

manage airway

manage CV collapse (pressors, fluids)

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26
Q

adverse or exaggerated physiological responses assoc. with central blocks

(Table 45-6)

A
  • urinary retention
  • high block
  • total spinal
  • cardiac arrest
  • anterior spinal artery syndrome
  • Horner syndrome
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27
Q

what is Horner syndrome?

A
  • unilateral sympathetic chain blockade
  • more assoc. with peripheral blocks
  • clinically looks like a stroke
  • resolves when block wears off
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28
Q

complications of central blockade related to needle/catheter placement

(Table 45-6)

A
  • backache
  • dural puncture/leak - PDPH, diplopia, tinnitus
  • neural injury
  • bleeding
  • misplacement (vascular injection, spinal, inadequate anesthesia)
  • catheter shearing/retention
  • inflammation
  • infection
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29
Q

complications of central blocks r/t drug toxicity

(Table 45-6)

A
  • systemic LA toxicity
  • TNS
  • cauda equina syndrome
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30
Q

what causes a PDPH (“spinal headache”)?

what techniques can cause it?

A

dural puncture occurs and dural closure is inadequate, resulting in CSF leakage

large needle, multiple attempts

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31
Q

classic symptoms of a spinal headache (PDPH)

A

headache that’s worse in upright position and relieved when supine

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32
Q

conservative treatment of spinal headache

A

rest, supine position, caffeine, hydration

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33
Q

management of a spinal headache if conservative measures fail

A

blood patch (20 mL blood used to “patch” dura)

should relieve within an hour or 2

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34
Q

why is a stylet used in a spinal block?

A

reduces likelihood of coring tissue during insertion

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35
Q

what is the purpose of non-cutting needles for spinal block?

A

cone-shaped tip designed to separate without cutting tissues

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36
Q

what is baricity?

A
  • LA density relative to the density of CSF
  • reflects the response of the injected LA to native CSF
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37
Q

isobaric solution

A

tends to stay in the same location

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38
Q

what is a hyperbaric solution?

A
  • denser, heavier than CSF
  • “sinks”
  • tend to move to the most dependent area of the spine (T4-T8 in supine position)
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39
Q

what happens when a hyperbaric LA solution is injected and the pt is in a head-down position?

(book)

A

solution spreads cephalad

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40
Q

what happens when a hyperbaric solution is given and the patient is put in a lateral position?

(book)

A

greater effect on dependent (down) side

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41
Q

common additive to make a solution hyperbaric

A

7.5% dextrose

(typically pre-mixed as hyperbaric bupivacaine)

of note, premixed hyperbaric bupivacaine has 8.25% dextrose in it

42
Q

what is a hypobaric solution?

A
  • less dense (lighter) than CSF
  • “floats”
43
Q

if you give a hypobaric LA solution and put the pt in a head-down position, where is the solution going to go?

(book)

A

caudad

44
Q

effect of a hypobaric solution move when pt is in a lateral position

(book)

A

greater effect on nondependent (up) side

45
Q

when might you use a hypobaric spinal?

A

to affect the left hip while lying on the right

46
Q

most important factors affecting the spread of spinal anesthesia

(table 45.2)

A
  • baricity of solution
  • position of patient during and immediately after injection
  • drug dosage
  • site of injection
47
Q

“other” factors affecting dermatomal spread of spinal anesthesia

(table 45.2)

A
  • age
  • CSF
  • curvature of spine/spinal stenosis
  • drug volume
  • intraabdominal pressure
  • needle direction
  • patient height
  • pregnancy
48
Q

advantages of using the midline approach over the paramedian approach

A
  • fewer angles
  • approach structures directly
  • offers widest portion of epidural space
49
Q

adverse effect of sympathetic blockade with central block

A

loss of vascular tone/SVR → hypotension

50
Q

how quickly will you see “sympathectomy” with spinal block?

how can you prevent this?

A

within minutes of injection

small doses of pressors, volume challenge (in eligible pts)

51
Q

what dermatome levels block cardioaccelerator nerves?

A

T1-T4

52
Q

adverse effect of cardioaccelarator nerve blockade

A
  • prominent, unopposed PNS stimulation (bradycardia)
  • may have profound hypotension, LOC
53
Q

adverse effect of neosynephrine for hypotension assoc. with sympathetic blockade

A

reflex bradycardia may result in asystole with a high-level spinal

54
Q

most prominent cervical spinous process

A

C7

55
Q

mL per dermatome initial dosing for lumbar epidural

(worksheet)

A

1-2 mL per segment (depending on pt height)

56
Q

dermatome that corresponds with the base of the scapula

A

T7

57
Q

dermatome that corresponds to the umbilicus

A

T10

58
Q

dermatome level that corresponds with the superior aspect of the iliac crests

A

L4

59
Q

how can blockade height be manipulated

A

by adjusting height and position at insertion

60
Q

bupivacaine dosing to block perineum & lower limbs (via spinal)

(table 45-4)

A

4-10 mg

61
Q

bupivacaine dose to block lower abdomen (via spinal)

(table 45-4)

is that what this means? sos

A

12-14 mg

62
Q

bupivacaine dose to block upper abdomen (via spinal)

(table 45-4)

A

12-18 mg

63
Q

how long does 0.75% bupivacaine in 8.25% dextrose last via spinal?

A

90-120 min

64
Q

how long does 0.75% bupivacaine in 8.25% dextrose + epi last via spinal?

A

100-150 min

(1.5-2.5 hrs)

65
Q

advantages of epidural vs spinal?

A
  • ability to create sensory blockade without motor blockade
  • can titrate dosage to change spread and clinical effect
  • can provide prolonged effect
  • less dense motor block
66
Q

disadvantages of epidural vs. spinal

A

larger needle placement =

  • increased risk of bleeding from inadvertent vessel injury
  • increased risk spinal headache if inadvertent subarachnoid puncture
67
Q

disadvantages of epidural vs. spinal

A

larger needle placement =

  • increased risk of bleeding from inadvertent vessel injury
  • increased risk spinal headache if inadvertent subarachnoid puncture
68
Q

how is clinical effect of an epidural acheived?

A

through both action on spinal roots as they pass through the epidural space and diffusion into CSF (where action is on spinal cord)

69
Q

tell me about the needle used for an epidural catheter placement

A

special needle that’s both blunted and curved

70
Q

what is the purpose of a blunted curved needle for access to epidural space for catheter placement?

A
  • blunting decreases likelihood of dural puncture
  • curvature protects dura by avoiding a piercing tip on the distal end
71
Q

2 techniques used to identify the epidural space

A
  1. loss of resistance
  2. hanging drop (using saline)
72
Q

what should you do if attempting to place an epidural catheter and you realize you’ve punctured the dura?

A

remove the needle and the catheter (if placed already)

do not withdraw the catheter from the needle - if the catheter must be withdrawn, remove the needle then the catheter

73
Q

test dose used for an epidural

A

3ml 1.5% lidocaine with 1:200,000 epi

(45 mg lidocaine, 15 mcg epi)

74
Q

effect of a higher concentration agent with less volume

A

greater density with less spread

75
Q

effect of a lower concentration agent with more volume

A

more diffuse but less intense blockade

76
Q

mL needed to block T10 to S5

A

12 mL

77
Q

does redosing of an epidural catheter require an additional test dose?

A

no, but should always be aspirated first

78
Q

if you’re trying to place an epidural but you lose resistance and see CSF when you remove the stylet, what should you do?

A

remove the needle, move up a level, try again :(

79
Q

2% chloroprocaine:

onset?

sensory block?

motor block?

A
  • onset - fast
  • sensory - analgesic
  • motor - mild to moderate
80
Q

3% chloroprocaine:

onset?

sensory block?

motor block?

A
  • onset: fast
  • sensory: dense
  • motor: dense
81
Q

≤ 1% lidocaine:

onset?

sensory block?

motor block?

A
  • onset: intermediate
  • sensory: analgesic
  • motor: minimal
82
Q

1.5% lidocaine:

onset?

sensory block?

motor block?

A

onset: intermediate
sensory: dense
motor: mild to moderate

83
Q

2% lidocaine:

onset?

sensory block?

motor block?

A
  • onset: intermediate
  • sensory: dense
  • motor: dense
84
Q

1% mepivacaine:

onset?

sensory block?

motor block?

A

onset: intermediate
sensory: analgesic
motor: minimal

85
Q

2-3% mepivacaine:

onset?

sensory block?

motor block?

A
  • onset: intermediate
  • sensory: dense
  • motor: dense
86
Q

≤ 0.25% bupivacaine:

onset?

sensory block?

motor block?

A
  • onset: slow
  • sensory: analgesic
  • motor: minimal
87
Q

0.5% bupivacaine:

onset?

sensory block?

motor block?

A
  • onset: slow
  • sensory: dense
  • motor: mild to moderate
88
Q

0.75% bupivacaine:

onset?

sensory block?

motor block?

A
  • onset: slow
  • sensory: dense
  • motor: moderate to dense
89
Q

0.2% ropivacaine:

onset?

sensory block?

motor block?

A
  • onset: slow
  • sensory: analgesic
  • motor: minimal
90
Q

0.5% ropivacaine:

onset?

sensory block?

motor block?

A
  • onset: slow
  • sensory: dense
  • motor: mild to moderate
91
Q

0.75% - 1% ropivacaine:

onset?

sensory block?

motor block?

A
  • onset: slow
  • sensory: dense
  • motor: moderate to dense
92
Q

if you’re trying to remove an epidural catheter and it won’t come out (yikes) what should you do?

A

put pt in placement position - may open spaces sufficiently to withdraw the catheter

93
Q

concentration of epidural lidocaine for sensory block

motor/surgical block?

A
  • sensory: ≤ 1%
  • motor: 2%
94
Q

concentration of epidural bupivacaine for a sensory vs. motor/surgical block

A
  • sensory: ≤ 0.25%
  • motor: 0.5%

*if he tries to get tricky, 0.75% best for motor but apparently unavailable

95
Q

concentration of epidural ropivacaine for a sensory block

A

0.2%

96
Q

concentration of chloroprocaine for a motor/surgical block

A

3%

97
Q
A
  1. C5
  2. T10
  3. L2
  4. L3
  5. L5
98
Q
A

A. C6

B. C7

C. C8

D. T1

E. T2

99
Q
A

A. C5

B. C6

C. S2

D. S1

100
Q

0.5% ropivacaine:

onset?

sensory block?

motor block?

A
  • onset: slow
  • sensory: dense
  • motor: mild to moderate
101
Q

Which neuraxial dose of opioids is similar to IV dosing?

A

Epidural

102
Q

Subarachnoid dosing of opoids is about ______% of IV dosing

A

10-20%

S5 - Regional/OB - Test 2 (9 decks)

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