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KDH: Principles (EXAM I) > Exam 1 Spinal & Epidural Neuraxial Anesthesia [5/30/24] - Anatomy/Dermatomes/Fibers > Flashcards

Exam 1 Spinal & Epidural Neuraxial Anesthesia [5/30/24] - Anatomy/Dermatomes/Fibers Flashcards

1
Q

What is the order of the meningeal layers from outter to inner?

A
  • Dura Mater
  • Arachnoid Mater
  • Pia Mater

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2
Q

List the 3 key spaces discussed in class.

A
  1. Epidural space
  2. Subdural space
  3. Subarachnoid space

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3
Q

Where is the epidural space?
What does it contain?

A
  • Located outside/before the dura mater.
  • Contains fat and small blood vessels (epidural veins).

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4
Q

What is the subdural space?

A
  • A potential space between the dura mater and the arachnoid mater.

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5
Q

Where is the subarachnoid space located?
What does it contain?

A
  • Between the arachnoid mater and the pia mater.
  • Filled with cerebrospinal fluid (CSF)
    * This is where we want the tip of the needle for spinal anesthesia.*

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6
Q

What 2 things might happen if the subdural space is hit?

A
  1. if its spinal it wont work
  2. if its epidural, will have high spinal block.

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7
Q

The epidural space is located around the spinal cord and has
specific boundaries defined by spinal structures. What are the boundaries of the Epidural Space?

A
  • Cranial Border
  • Caudal Border
  • Anterior Border
  • Lateral Borders
  • Posterior Borders:At the back,framed by ligamentum flavum and the bony plates of the vertebrae (vertebral lamina).

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8
Q

Where does the epidural space start and end?
Clinical relevance?

A
  • Starts: Foramen mangum
  • Ends: S5
  • Wide range you can cover meaning we can administer the epidural anesthesia from foramen magnum to S5 . Can do epidural anesthesia in thoracic, lumbar, caudal.

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9
Q

List the contents of the epidural space

A

Contains nerves, fatty tissue,lymphatics,and blood vessels.

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10
Q

What is the role of the contents of the epidural space?

A
  • Aids in drug absorption.
  • Ex: bupivacaine is absorbed more than lidocaine or fentanyl or morphine

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11
Q
  • Epidural vein is also called?
  • What are the characteristics of the epidural vein?
A
  • Batson’s Plexus
  • Valveless and form a plexus draining blood from the cord and its linings
  • Density of veins increases laterally
  • Engorged under conditions like obesity or pregnancy, increasing the risk during needle procedures in this area.

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If getting blood, then you are injecting laterally and not midline!

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12
Q

Plica Mediana Dorsalis

  1. Plica Mediana Dorsalis is for spinals or epidurals?
  2. What is it?
  3. What is its impact?
A
  1. Epidurals only.
  2. Thought to be a band of connective tissue located between the ligamentum flavum and the dura mater
  3. If it exists, it might act as a barrier within the epidural space which could affect how medications spread when injected into the epidural space.
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13
Q

What is the clinical relevance of Plica Mediana Dorsalis

A
  • Difficult Catheter Insertion
  • Unilateral Blocks: It might also play a role in cases where an epidural does not equally affect both sides of the body.

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14
Q

Subarachnoid Space

Where is the subarachnoid space?
What does it contain?

A
  • Located deep to the arachnoid mater| in between arachnoid and pia mater.
  • Contains cerebrospinal fluid (CSF), nerve roots, and the spinal cord itself.

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15
Q

This space is the primary target when performing a spinal anesthetic procedure

A

Subarachnoid Space

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16
Q

What is the characteristic Sensation when performing a spinal anesthesia?

A
  • “POP”
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17
Q

The subdural space is a ____ located b/w which 2 layers around the spinal cord?

A

Potential space
dura mater (outer layer) and arachnoid mater (middle layer)

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18
Q

If we accidentally place an epidural in the subdural space what would the clinical effect be?

A

“high spinal” effect meaning the medication affects a larger area than intended

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19
Q

If we inadvertently place a spinal dose in the subdural space what would the result be?

A

failed spinal block
(it wont work!!!)

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20
Q

T/F
The Dura mater extends from the magnum foramen to L3

A

False
It extends from the foramen magnum to the dural sac (which ends at S2 in adults and S3 in infants)

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21
Q

T/F
the pia mater lacks vasculature

A

FALSE!
The pia mater is HIGHLY vascular

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22
Q

Where is the pia mater located?
Should the spinal needle punture this layer of meninges?

A

this innermost layer directly covers the spinal cord
NO!! it should NEVER be punctured as it is directly attached to the surface of the spinal cord

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23
Q

How mant spinal nerves do we have total? at each level of the spinal cord?

A

31 spinal nerves!
C-8
T-12
L-5
S-5
Coccyx-1

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24
Q

Where do the spinal nerves exit for thoracic, lumbar, sacral, and coccyx nerves?

A

below the vertebra they are named for

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25
Q

Each spinal nerve is formed by the joining of what?

A

2 nerve roots:
Anterior (Motor) and Posterior (Sensory) nerve roots

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26
Q

What is a dermatome?

A

An area of skin that receives sensory nerves from a single spinal nerve root

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27
Q

T/F
While a dermatome may physically appear to align w/ a certain part of the spine, it is actually connected to a different spinal nerve root

A

TRUE

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28
Q

L1,2,3,4 dermatomes cover

A

anterior and inner surface of the lower limbs

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29
Q

L4,5 S1 dermatomes cover

A

foot

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30
Q

L4 dermatome covers

A

medial side of great toe

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31
Q

S1,2 L5 dermatome covers

A

posterior and outer surface of lower limbs

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32
Q

S1 dermatome covers

A

Lateral margin of foot and little toe

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33
Q

S2,3,4 dermatome covers

A

Perineum

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34
Q

T10 dermatome covers

A

Umbilicus

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35
Q

T12 dermatome covers

A

Inguinal or groin regions

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36
Q

C5 dermatome covers

A

Clavicles

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37
Q

C5,6,7 dermatomes cover

A

lateral parts of upper limbs

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38
Q

C8, T1 dermatomes cover

A

Medial sides of upper limbs

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39
Q

C6 dermatome covers

A

Thumb

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40
Q

C6,7,8 dermatomes cover

A

Hand

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41
Q

C8 dermatome covers

A

Ring and little fingers

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42
Q

T4 dermatome covers

A

Nipples

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43
Q

Which Nerve transmits facial sensations? What are its branches?

A

Trigeminal Nerve (CN-V)
V1- opthalmic
V2- maxillary
V3- mandibular

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44
Q

what is the dermatome for peri-anal/anal surgery aka saddle block?

A

S2-S5

slide 41

45
Q

Desired dermatome for foot/ankle surgery?

A

L2

slide 41

46
Q

Desired dermatome for thigh/lower leg/knee surgery?

A

L1

slide 41

47
Q

Desired dermatome for vaginal delivery/uterine/hip procedure/ tourniquet/ TURP?

A

T10

slide 41

48
Q

Desired dermatome for scrotum surgery?

A

S3

slide 41

49
Q

Desired dermatome for penis surgery?

A

S2

slide 41

50
Q

Desired dermatome for testicular procedures?

A

T8
testicles are embryonically derived from the same lavel as the kidneys for pain transmission [T10-L1]

slide 41

51
Q

Desired dermatome for urologic/gynecologic/lower abdominal surgery?

A

T6

sliide 41

52
Q

Desired dermatome for ceseran section/upper abdominal surgery?

A

T4
sometimes may require concomitant genreral anesthesia d/t vagal stimulation form abdominal traction

slide 41

53
Q

For Epidurals to work effectively we need the LA to ___ through the dural cuff to reach the ___.

A

diffuse

Nerve Roots

slide 43

54
Q

what are controllable factors that affect the spread of spinals? (4)

A
  • Baricity
  • Patient Position
  • Dose
  • Site of Injection

Barry Plucked Dos Shallots

slide 44

55
Q

what are the non-controllable factors that affect the spread of spinals? (3)

A
  • Volume of CSF (Less CSF = Higher the blockade)
  • Increased Intra-abdominal Pressure (obesity,pregnancy)
  • Age (elderly)

slide 44

56
Q

what are the factors that dont affect the spread of spinals?

A
  • Barbotage (repeated aspiration and reinjection of CSF)
  • Speed of Injection
  • Bevel orientation
  • Addition of Vasoconstrictor
  • Gender

slide 44

57
Q

what are the key points to remember for spinals? (5)

A
  • dose is crucial
  • baracity matters
  • low csf volume
  • advanced age
  • pregnanacy

slide 44

58
Q

why is dosing crucial for spinals?

A

It’s the most reliable factor affecting how far and wide the anesthetic spreads when using a hypo- or isobaric solution.

slide 44

59
Q

why is pregnancy an important factor to consider with spinals?

A

Decreased CSF volume due to increased intraabdominal pressure.

slide 44

60
Q

what are controllable factors that significantly affect the spread of epidurals (3)

A
  • Local Anesthetic Volume: Most important drug related factor
  • Level of injection: Most important procedure related factor
  • Local Anesthetic dose

slide 45

61
Q

what are non-controllable factors that significantly affect the spread of epidurals (2)

A
  • Pregnancy
  • Old Age

slide 45

62
Q

what are controllable factors that have small affect on the spread of epidurals

A
  • Local Anesthetic Concentration
  • Patient Position

slide 45

63
Q

what are non-controllable factors that have small affect on the spread of epidurals

A

height (Taller or shorter stature may slightly affect spread)

slide 45

64
Q

what are controllable factors that have no affect on the spread of epidurals

A
  • Additives in the Anesthetic (Might change onset time or duration but not spread.)
  • Direction of the Bevel of the Needle
  • Speed of Injection

slide 45

65
Q

Injection Levels and Spread Dynamics:
* Lumbar Region:
* Mid Thoracic Region:
* Cervical Region:

A
  • Lumbar Region: mostly spreads cephalad.
  • Mid-Thoracic Region: Spread is balanced both cephalad and caudad.
  • Cervical Region: spreads caudad

slide 45

66
Q

what are the 3 nerve fiber types?

A

A fibers
B fibers
C fibers

slide 46

67
Q

what are the different subtypes of A fibers?

A
  • alpha
  • beta
  • gamma
  • delta

slide 46

68
Q

Which nerve fiber has the largest diameter and which one has the smallest?

A
  • largest: A-alpha
  • smallest: C fibers

slide 46

69
Q

how are the nerve fibers blocked? [first to last?]

A
  • 1st: B fibers
  • 2nd: C fibers
  • 3rd: A-gamma and A-delta
  • 4th: A-alpha and A-beta

slide 46

This is also how they are arranged!!

70
Q

what is differential blockade?

A

Differential blockade refers to how different types of nerve fibers have varying sensitivities to local anesthetics, affecting the level of block achieved.

slide 47

71
Q

Between sensory and autonomic blockade, which requires less concentration of LA?
Which one results in the highest level of blockade?

A

Autonomic and Autonomic

slide 47

72
Q

In the Differential Blockade Zones:
* The ____ is 2 levels higher than the motor level
* The sympathetic level is ___-___ levels higher than the sensory level

A

Sensory level
2-6

slide 48

73
Q
  • What two sensory aspects travel together?
A
  • temperature and pain

slide 48 talking

74
Q

Onset of nerve blockade sequence

A
  1. B-fibers: sympathetic
  2. C and A-delta = loss of pain and temperature
  3. A-gamma= loss of motor tone
    A-beta= loss of touch and pressure
    A-alpha= loss of motor function and proprioception

slide 49

75
Q

Recovery of Nerve blockade sequence

A
  1. A-alpha, Beta, Gamma
  2. C and A-delta
  3. B fibers

slide 49

76
Q

Which nerve fibers are blocked the longest?

A

B fibers - they are the first on, and last off

question in lecture

77
Q

Order in which senses are blocked.

A
  • Temperature - this is the first sense to be blocked
  • Pain - second sense to be blocked
  • Touch/Pressure - last sense to be blocked

slide 50

78
Q

How to monitor Motor block? and what is this monitoring scale called?

A
  • Modified Bromage Scale
  • Scale levels:
    0: no motor block
    1: slight motor block - pt cannot raise leg, but can move knees and feet
    2: moderate motor block: cannot raise leg or move knee, but can move the feet
    3: complete motor block: cannot move lower extremities (legs, knees or feet)

slide 50

79
Q

The Modified Bromage Scale specifically evaluates what?

A

the function of lumbosacral nerves

Slide 50

80
Q

Why does preload decrease when performing neuraxial anesthesia?

A

Preload will decrease because of sympathectomy (venous dilation which pools blood in periphery and decreases venous return)

slide 51

81
Q

CV effects of neuraxial anesthesia: Afterload
* how much does SVR decrease in healthy vs Elderly/cardiac pts?

A

Afterload decreases - sympathectomy partially dilates the arterial circulation
* Healthy pts: SVR decreases by ~15%
* Elderly or cardiac pts: SVR can decrease up to ~25%

slide 51

82
Q

Why does C.O. decrease when performing neuraxial anesthesia?

A

decrease in venous return and SVR

slide 51

83
Q

Why does heart rate decrease in neuraxial anesthesia?

A
  • blockade of cardiac accelerator fibers (T1-T4) blocks SNS tone
  • Activation of reflexes:
    1. Benzold-Jarish Reflex
    2. Reverse bainbridge reflex

slide 51

84
Q

The Bezold-Jarisch Reflex is a response caused by ___ which could lead to ___.

A

ventricular underfilling
significant bradycardia

slide 51

85
Q

The Bezold-Jarisch reflex is mediated by ___ receptors, located in the ___ nerve and the ___.

A

5-HT3

Vagus

Ventricular myocardium

86
Q

What triggers the Reverse Bainbridge reflex

A

reduced stretching of the RA

slide 51

87
Q

What population is more likely to have sudden cardiac arrest?
How often is sudden cardiac arrest seen after spinals/epidurals?

A
  • Can be seen young adults with high parasympathetic tone
  • 7:10,000 spinals
  • 1:10,000 epidurals

slide 52

88
Q

How long after a neuraxial block is given would you see a cardiac arrest?

A
  • 20-60 min after onset of spinal

slide 52

89
Q

Prevention of spinal-anesthesia induced HoTN: prevention with drugs (2 drugs)

A
  • Vasopressors: phenylephrine
  • 5-HT3 Antagonists: ondansetron

slide 53

90
Q

Fluid Management methods to prevent spinal-anesthesia induced hypotension:

A
  • Co-loading
  • Avoid Preloading
  • Avoid Excess Fluids

slide 53

91
Q

Describe “Co-loading”

A

Administering intravenous fluids (around 15 mL/kg) right after the spinal block to prevent drops in blood pressure.

92
Q

Drug Treatment of spinal-anesthesia induced HoTN:

A
  • Vasopressors: ephedrine, epinephrine, phenylephrine
  • Anticholinergics: Atropine (rarely = lasts too long)

slide 54

93
Q

Why do we want to be cautious when doing position changes for Treatment of Spinal-Anesthesia Induced Hypotension?

A

> 20-degree tilt can reduce cerebral perfusion because the tilt can reduce venous brain drainage.

If the block is not set yet, the block height can increase due to gravity

slide 54

94
Q

True or False:
Pulmonary Effects from neuraxial anesthesia are usually minimal.

A

TRUE

95
Q

These two flow-volume loop measurements are DECREASED after neuraxial anesthesia

A

ERV
VC

96
Q

Where are our Phrenic nerves? (Dermatomes)

A

C3-C5

97
Q

GI System effects with Neuraxial Anesthesia

Parasympathetic innervation is primarily via the ___.
Sympathetic innervation of GI tract stems from ___.

A

Vagus Nerve
T5-L2

98
Q

What are the impacts of neuraxial anesthesia on the GI system?

A

Reduces Sympathetic tone
Increases Parasympathetic activity

99
Q

Sympathetic blockade above ___ affects bladder control.

A

T10

100
Q

Systemic Effects of Neuraxial Anesthesia on the Genitourinary system

The addition of neuraxial opioids will cause what 2 things?

A

Decrease in detrusor contraction
Increase in bladder capacitance

101
Q

True or False:
Foley catheters are not required for neuraxial anesthesia cases.

A

FALSE

KDH: Principles (EXAM I) (7 decks)

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