Neuraxial Principles Flashcards

1
Q

ASRA

normal PT (prothrombin time)
What pathway does it measure?

A

12-14 seconds
* extrinsic pathway

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2
Q

ASRA

Normal International normalized ratio (INR)

What pathway does it measure?

A

0.8-0.11

  • extrinsic pathway
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3
Q

ASRA

Normal Activated Partial Thromboplastin Time (aPTT)

What pathway does it measure?

A

25-32 seconds

  • extrinsic pathway
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4
Q

ASRA

Normal Bleeding Time

what is it related to?

A

3-7 minutes

  • r/t platelet aggregation/activation/adhesion
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5
Q

ASRA

Normal Platelet Levels

A

150,000 - 300,000 mm3

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6
Q

Intrinsic Pathway Factors

A

“if you can’t buy the intrinsic pathway for $12, you can buy it for $11.98

  • XII, XI, IX, VIII
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7
Q

Extrinsic Pathway Factors

A

“For 37 cents, you can purchase the extrinsic pathway”

  • III, VII
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8
Q

Final Common Pathway Factors

A

“The final common pathway can be purchased at the five (V) and dime (X) for 1 (I) or 2 (II) dollars on the 13th (XIII) of the month”

  • V, X, I, II, XIII
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9
Q

Spine Landmarks

C7

A

Vertebra Prominens

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10
Q

Spine Landmarks

T3

A

Root of Spine of Scapula

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11
Q

Spine Landmarks

T7

A

Inferior Angle of Scapula

  • good place to do a thoracic epidural
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12
Q

Spine Landmarks

What is the rib margin from midline @ L1?

A

10cm

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13
Q

Spine Landmark

L4

A

Superior Aspect of Iliac Crest

  • important for central neuraxial
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14
Q

Spine Landmark

S2

A

Posterior Superior Iliac Spine

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15
Q

Spine Landmarks

What is the Intercristal line (Tuffier’s Line)?

A
  • A horizontal line that runs across the top edges of the hip bones (iliac crests)
  • matches the L4 vertebra
  • helps identify spaces b/w vertebra for inserting spinal anesthesia needles
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16
Q

Spine Landmarks

What does the space above Tuffier’s Line align with?

A

L3-L4 vertebrae

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17
Q

Spine Landmarks

What does the space below Tuffier’s line align with?

A

L4-L5

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18
Q

Where does the spinal cord end?

A
  • Adults - L1
  • Peds - L3
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19
Q

Spine Landmarks

What area does the intercristal line correspond to in infants up to 1 yr old?

A

L5-S1 intervertebral space

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20
Q

Spine Landmarks

What are the landmarks for caudal anesthesia?

A

Sacral Cornu

  • LA goes in the sacral hiatus that is covered by the sacrococcygeal ligament
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21
Q

Where does the spinal cord start & end?

A

Starts - Medulla Oblongota (rostral region)

Ends - Conus Medullaris (L1)
*b/w L1-L2 in adults

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22
Q

Where does the cauda equina extend from?

A

conus medullaris — dural sac
* nerve roots from L2-S5 vertebrae & coccygeal nerve

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23
Q

Where does the dural sac end?

A

S2 in adults, S3 in infants

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24
Q

Where does the filum terminale extend from?

What is its purpose?

A
  • extends from conus medullaris to coccyx (continuation of pia mater)
  • function is to anchor spinal cord to coccyx
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25
Q

Internal Filum Terminale Location

A

Extends from conus medullaris to dural sac (L1-S2)

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26
Q

External Filum Terminale Location

A

Extends from dural sac into the sacrum (S2-S5)

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27
Q

What signal does the anterior spinal cord take care of?

A

Motor

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28
Q

What signal does the posterior spinal cord take care of?

A

Sensory (S after M - so sensory in the back)

  • PS - i love neuraxials
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29
Q

Is the afferent nerve sensory or motor?

A

sensory - toward the brain (ascending limb)

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30
Q

Is efferent sensory or motor?

A

motor - away from the brain (descending)

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31
Q

Order of Meningeal layers from outer to inner

A
  1. Dura Mater: outermost
  2. Arachnoid Mater: middle layer
  3. Pia Mater: innermost (covers the spinal cord)
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32
Q

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

A
  • located outside the dura mater (before the dura)
  • contains fat and small epidural veins
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33
Q

Where is the subdural space located?

A
  • potential space b/w dura mater & arachnoid mater
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34
Q

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

A
  • b/w the arachnoid mater and pia mater
  • contains CSF - cushions/protects the cord
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35
Q

What is the cranial border of the epidural space?

A

Foramen Magnum

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36
Q

What is the caudal border of the epidural space?

A

Sacrococcygeal ligament (S5 - coccyx)

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37
Q

What is the anterior border of the epidural space?

A

posterior longitudinal ligament

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38
Q

What are the lateral borders of the epidural space?

A

vertebral pedicles

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39
Q

What are the posterior borders of the epidural space?

A

ligamentum flavum & vertebral lamina

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40
Q

What are the contents of the epidural space?

A
  • nerves, fatty tissue, lymphatics, blood vessels
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41
Q

What is Batson’s Plexus?

A
  • plexus formed by valveless epidural veins that drain blood from the cord and its linings
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42
Q

When are epidural veins more engorged?

A
  • density increases laterally
  • engorged in obesity & pregnancy
43
Q

When do we do a paramedian approach with epidural placement?

A
  • positioning issues
  • spinal deformitities (disc issues)
44
Q

What is the Plica Mediana Dorsalis?

A
  • band of connective tissue located b/w ligamentum flavum & dura mater
45
Q

The _______ _______ ________ can act as a barrier in the epidural space & affect how medications spread.

A

Plica Mediana Dorsalis

46
Q

What are 4 things we can do to help w/ a unilateral epidural block?

A
  1. re-position the pt
  2. give narcotics (in the epidural)
  3. pull the catheter out 1cm
  4. re-do the epidural
47
Q

Where can epidural anesthesia be done?

A
  1. Thoracic
  2. Lumbar
  3. Caudal
48
Q

Where is the SA space located?

A

b/w the arachnoid & Pia mater

49
Q

Is the SA space a potential space?

A

No. It contains CSF, nerve roots, spinal cord

50
Q

Where is the primary target for a spinal anesthetic?

A
  • SA space
51
Q

Where is the Subdural space located?

A
  • potential space in b/w the dura and arachnoid mater
52
Q

What can happen when LA intended for epidural space goes to subdural space?

A
  • can cause a high spinal - med affects larger area than intended
53
Q

What can happen when LA intended for spinal use is injected into subdural space?

A
  • failed spinal block
54
Q

What is the tough fibrous shield that protects the spinal cord?

Where is its location?

A
  • Dura mater
  • starts @ foramen magnum goes down to dural sac
55
Q

What is the thin layer of connective tissue that lies beneath the dura mater?

A

Arachnoid Mater

56
Q

What is the thin paper meningeal layer attached to the cord?

It is highly ________.

A

Pia Mater

  • vascular
57
Q

How many spinal vertebrae and nerves are there?

A
  • 33 vertebrae
  • 31 nerves
58
Q

Spinal nerve locations & #

A
  • Cervical - 8
  • Thoracic - 12
  • Lumbar - 5
  • Sacral - 5
  • Coccyx -1
59
Q

What is special about the C1-C7 nerves?

A

They exit above the corresponding vertebrae

60
Q

What does the Anterior (ventral) nerve root carry?

A
  • motor (movement) & autonomic body processes info from spinal cord to body
61
Q

What does the Posterior (Dorsal) nerve root carry?

A
  • sensory information from the body to the spinal cord
62
Q

What is the clinical significance to understanding sensory dermatomes?

A
  • tells you where your block levels is (sensory)
  • important to know for surgical procedures
63
Q

What are the target nerves for spinal (intrathecal) anesthesia?

A
  • cauda equina (below L1, conus medullaris)
  • LA works on myelinated preganglionic fibers of the spinal nerve roots
64
Q

How does epidural LA work?

A
  • it diffuses through the dural cuff - reaches nerve roots @ level we want to block
65
Q

Controllable Factors that affecct SPINAL spread:

A
  1. Baricity
  2. pt position
  3. dose
  4. site of injection (L3/L4, L4/L5)
66
Q

Non-controllable Factors that affect SPINAL spread:

A
  1. Volume of CSF
    * lower volume = higher block
67
Q

Who are pts that have a lower volume of CSF?

A
  • increased intra-abdominal pressure (obesity, pregnancy, ascites)
  • Elderly
68
Q

What does NOT affect the spread of a SPINAL anesthetic?

A
  1. Barbotage
  2. speed of injection
  3. orientation of bevel
  4. addition of vasoconstrictor & other adjuncts (duration)
  5. Gender
69
Q

Controllable factors that have a significant affect on EPIDURAL LA spread:

A
  1. LA volume (drug related)
  2. level of injection (procedure related)
  3. LA dose
70
Q

Non-controllable factors that significantly affect EPIDURAL LA spread:

A
  1. pregnancy
  2. old age
71
Q

Controllable Factors that have a small effect on EPIDURAL LA spread:

A
  1. LA concentration
  2. Pt position
72
Q

Non-controllable factors that have a small effect on EPIDURAL LA spread:

A
  1. Height (taller or shorter)
    * shorter people need less
73
Q

Factors that DO NOT effect EPIDURAL LA spread:

A
  1. additives in LA
  2. orientation of bevel
  3. speed of injection
74
Q

Where does lumbar LA spread?

A

cephalad

75
Q

Where does mid-thoracic LA spread?

A

balanced b/w cephalad & caudad

76
Q

Where does cervical LA spread?

A

caudad

77
Q

Nerve Fibers

A-alpha
myelination:
function:
diameter:
Block Onset:

A
  1. heavy myelination
  2. function: skeletal muscle (motor), proprioception
  3. Diameter: 12-20 micrometers
  4. Block: 4th
78
Q

Nerve Fibers

A-beta
myelination:
function:
diameter:
Block onset:

A
  1. heavy myelination
  2. function: touch, pressure
  3. diameter: 5-12 micrometers
  4. block onset: 4th
79
Q

Nerve Fibers

A-gamma
myelination:
function:
diameter:
block onset:

A
  1. medium myelination
  2. function: skeltal muslce (tone)
  3. diameter: 3-6 micrometers
  4. Block onset: 3rd
80
Q

Nerve Fibers

A-delta
myelination:
function:
diameter:
block onset:

A
  1. medium myelination
  2. function: fast pain, temp, touch
  3. diameter: 2-5 micrometers
  4. block onset: 3rd
81
Q

Nerve Fibers

B-fibers
myelination:
function:
diameter:
block onset

A
  1. light myelination
  2. function: preganglionic ANS fibers
  3. diameter: 3 micrometers
  4. block onset: 1st
82
Q

Nerve Fibers

C-fibers (sympathetic)
myelination:
function:
diameter:
block onset:

A
  1. myelination: none
  2. function: postganglionic ANS fibers
  3. diameter: 0.3-1.3 micrometers
  4. block onset: 2nd
83
Q

Nerve Fibers

C-fibers (dorsal root)
myelination:
function:
diameter:
block onset:

A
  1. myelination: none
  2. function: slow pain, temperature, touch
  3. diameter: 0.4-1.2 micrometers
  4. block onset: 2nd
84
Q

Nerve Fibers

block onset order (list)

A
  1. B-fibers
  2. C-fibers (sympathetic & dorsal root)
  3. A-delta, A-gamma
  4. A-beta, A-alpha
85
Q

Where is the sensory level of LA block located?

A
  • 2 levels higher than motor blockade
86
Q

Where is the sympathetic level of LA blockade located?

A

2-6 levels higher than sensory level (sympathetic chain)

87
Q

Blockade level example:
T8 location
motor block?
SNS block?

A

motor: T10
SNS: T2-T6

88
Q

Why does sensory block happen at a higher level than motor blockade?\

Autonomic?

A

Sensory requires lower concentrations of LA

  • requires even lower concentration levels of LA
89
Q

Sense block order (first to last)

A
  1. temperature (alcohol swab)
  2. pain (pinprick)
  3. touch/pressure
90
Q

What scale is used to assess motor blockade?

What does it evaluate?

A

Modified Bromage Scale
* evaluates function of lumbosacral nerves – nothing above this!

91
Q

Modified Bromage Scale

0

A

no motor block

92
Q

Modified Bromage Scale

1

A
  • slight motor block
  • ex: cannot raise leg but still move knee & foot
93
Q

Modified Bromage Scale

2

A

Moderate Motor Block
* ex: cannot raise extended leg or move knee - can move feet

94
Q

Modified Bromage Scale

3

A

Complete motor block
* ex: cannot move legs, knees, or feet

95
Q

What 2 things should we have prepared with every spinal/epidural?

A
  1. Ephedrine (HR low)
  2. Phenylephrine (HR high)
96
Q

Diaphragm nerve

A

C4

97
Q

Heart Nerve

A

T3-T4

98
Q

Esophageal Nerve

A

T4-T5

99
Q

Stomach Nerve

A

T8

100
Q

Liver & Gallbladder Nerve

A

T8-T11

101
Q

Small Intestine Nerve

A

T10

102
Q

Colon Nerve

A

T11

103
Q

Kidney & Testes Nerve

A

T10-L1

104
Q

Bladder Nerve

A

T11-L1