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Principles of Anesthesia > Neuraxial (Exam 1) > Flashcards

Neuraxial (Exam 1) Flashcards

1
Q

What type of neuraxial anesthesia is pediatric specific?

A

Caudal

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2
Q

What are some clinical indications for neuraxial anesthesia?

A
  • surgical procedures involving the lover abdomen, perineum, and lower extremities
  • orthopedic surgery and cesarian sections
  • vascular surgeries on the legs

Slide 5

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3
Q

What type of procedures would neuraxial anesthesia be used as an adjunct to GETA?

A

Thoracic surgeries

GETA is still primary, we can use an epidural (not spinal) as an adjunct to maintain anesthesia in the OR or help with postop pain.

slide 5

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4
Q

What are the 6 main benefits to neuraxial anesthesia discussed in class?

A

REDUCED:
* postop ileus
* narcotic usage
* bleeding
* respiratory complications
* PONV
* thromboembolic events

slide 6

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5
Q

What are some other benefits to neuraxial anesthesia?

besides the 6 main ones

A
  • better mental alertness
  • less urinary retention
  • pts quicker to eat, void, ambulate
  • fewer overnight admissions from GA complications
  • quicker PACU discharge times
  • blunts stress response from surgery

slide 7

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6
Q

If the patient is talking and awake during surgery and needs to be asleep, what is Tito’s preferred drug and dose to add to neuraxial to help with this?

given IV, not through neuraxial

A

propofol

TxWes: 50-150 mcg/min
Tito’s recipe: 7ml push and 150 mcg/min gtt

slide 7

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7
Q

What are 4 relative contraindications to neuraxial anesthesia?

A
  1. deformities of the spinal column (kypho, lordo, scoliosis)
  2. pre-existing diseases of the spinal cord (MS, post-polio syndrome)
  3. Chronic headache/backache
  4. Inability to perform SAB/epidural after 3 attempts

Slide 8

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8
Q

Why are the relative contraindications just relative? What happens if we do the neuraxial anyway?

A

Symptoms will likely worsen. We need to discuss this with the patient pre-op to set expectations for what may happen if we do the neuraxial.

slide 8

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9
Q

What are 8 absolute contraindications to neuraxial anesthesia?

A
  1. Coagulopathy (risk of epidural hematoma)
  2. Pt refusal
  3. Evidence of dermal site infection
  4. Severe or critical valvular heart disease
  5. HSS (Idiopathic hypertrophic subaortic stenosis)
  6. Surgery lasting longer than the duration of the anesthetic
  7. Increased ICP
  8. Severe CHF

Slide 9 & 10

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10
Q

What is the ASRA’s INR parameters for neuraxial contraindication?

“American Sociaty of Regional Anesthesia and Pain Medicine”

A

INR > 1.5

slide 9

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11
Q

What platelet level is a neuraxial contraindication?

A

Platelets < 100,000

Have to look at trends with this. If plt is 110,000 down from 150,000 fast, dont do it. If plt baseline is 90,000 and hasnt changed in months, can maybe do it.

slide 9

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12
Q

What is normal prothrombin time (PT) and what part of coag cascade does it measure?

A

12-14 seconds
Extrinsic pathway

slide 9

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13
Q

What is normal INR and what part of coag cascade does it measure?

A

0.8 to 1.1
Extrinsic pathway

slide 9

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14
Q

What is normal activated partial thromboplastin time (aPTT) and what part of coag cascade does it measure?

A

25-32 seconds
Intrinsic

slide 9

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15
Q

What is normal bleeding time (BT) and what part of coag cascade does it measure?

A

3-7 minutes
measures primary plt activation and aggregation

slide 9

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16
Q

What is normal plt levels?

A

150,000 - 300,000

slide 9

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17
Q

What is the clotting cascade order?

A

Intrinsic:
* XII
* XI
* IX
* VIII

Extrinsic:
* III
* VII

Final Common Pathway:
* X
* V
* II
* I
* XIII

slide 9

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18
Q

What is the saying to remember the clotting cascade in terms of money?

A

“If you cant buy the intrinsic pathway for $12, you can buy is to $11.98.
For 37 cents you can buy the extrinsic pathway.
The final common pathway can be purchased at the five and dime for 1 or 2 dollars on the 13th of the month.”

slide 9

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19
Q

What valve size is considered severe aortic stenosis and mitral stenosis?

A

AS ≤ 1.0 cm2
MS < 1.0 cm2

slide 10

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20
Q

What is the clinical triad of aortic stenosis and the life expectancy at each stage?

A
  1. Angina (5 yrs)
  2. Syncope (3 yrs)
  3. Failure and SOB (2 yrs)

slide 10

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21
Q

What happens in critical valve patients if we have decreased SVR from anesthesia drugs?

A

DEATH SPIRAL

hypotension causes myocardial ischemia which leads to ischemic contractile dysfunction which leads to decreased cardiac outpit which causes worsening hypotension which causes more ischemia forever until you d.e.a.d.

slide 10

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22
Q

What happens if your operation lasts longer than the duration of the neuraxial anesthesia you gave?

A

Have to convert to GA mid procedure.

sometimes we have to do this anyway but we dont want to because then we have all the bad side affects of GA that we were trying to avoid by giving neuraxial

slide 10

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23
Q

What is the onset comparison between spinal vs. epidural?

A

Spinal: rapid (about 5 minutes)
Epidural: slow (10-15 minutes)

slide 11

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24
Q

What is the spread comparison between spinal vs. epidural?

A

Spinal: higher than expected and may extend extracranially
Epidural: As expected, can be controlled with volume of local anesthetic delivered

slide 11

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25
Q

What is the nature of block comparison between spinal vs. epidural?

A

Spinal: Dense (blocks a lot and fast with very little medication)
Epidural: Segmental (nature of the block depends on the dose and where you place it)

slide 11

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26
Q

What is the motor block comparison between spinal vs. epidural?

A

Spinal: Dense (pt wont be able to move below the block)
Epidural: Minimal (pt is still a high fall risk but in other countries, laboring moms with epidurals are allowed to walk around)

slide 11

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27
Q

What is the hypotension comparison between spinal vs. epidural?

A

Spinal: likely and drastic
Epidural: less than with spinal

Remember the BP of baby is determined by the BP of mom until they are delivered so decr. BP leads to decels and lower APGAR at delivery

slide 11

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28
Q

What is the duration comparison between spinal and epidural?

A

Spinal: limited and fixed (inject medication and then d/c access)
Epidural: unlimited (catheter stays in place)

slide 12

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29
Q

What is the placement level comparison between spinal and epidural?

A

Spinal: L3-L4 (bigger space), L4-L5 (safest for learning), L5-S1
Epidural: any spinal level

slide 12

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30
Q

How do we dose spinal vs epidural?

A

Spinal: dose based (mg)
Epidural: volume based (ml)

slide 12

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31
Q

Is spinal or epidural more difficult according to slide 12 table?

A

epidural requires more skill

slide 12

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32
Q

Which neuraxial poses a risk for LA toxicity?

A

only epidural

subarachnoid blocks require such small doses to acheive block, we dont have a risk for toxicity

slide 12

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33
Q

How does gravity influence spinal vs. epidural?

A

spinal: influenced by baricity (whether the drug sinks or floats)
epidural: influenced by patient position

slide 12

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34
Q

How many vertebra do we have and what is the split?

A

33 total
7 cervical
12 thoracic
5 lumbar
5 sacral (fused)
4 coccyx (fused)

slide 13

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35
Q

What is the ligament connecting the sacrum to the coccyx?

A

sacrococcygeal ligament

slide 14

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36
Q

What are the two main structures of vertebra?

A

body (anterior) and vertebral arch (posterior)

slide 15

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37
Q

What two structures link the anterior and posterior segments of the vertebral arch?

A

lamina (posterior) and pedicle (anterior)

slide 15

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38
Q

What is housed in the vertebral foramen created by the vertebral arches of the vertebra?

A

spinal cord, nerve roots, epidural space

slide 15

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39
Q

What are the processes that come off of the vertebral arch?

A

transverse processes (lateral)
spinous processes (posterior midline)

slide 16

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40
Q

How are the lumbar vertebrae different from the cervical and throacic?

A

The angle of the spinous processes is greater allowing for easer needle access.

slide 17

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41
Q

What is the landmark where the spinal nerves exit the spine?

A

intervertebral foramina

slide 18

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42
Q

What forms the facet joints of vertebra?

A

the inferior articular process of the superior vertebra and the superior articular process of the inferior vertebra

slide 19

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43
Q

What do the facet joints do?

A

guide and limit spines movement

slide 19

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44
Q

What happens if the facet joint suffers an injury impact?

A

It can press on nearby spinal nerves. That pressure can cause pain and muscle spasms in that spinal nerves dermatome.

slide 19

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45
Q

What level of the spine is the superior aspect of the iliac crest?

A

L4

slide 20

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46
Q

What level of the spine is the posterior superior iliac spine?

A

S2

slide 20

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47
Q

What is the line called that relates to the superior iliac crest being the same level as L4?

A

Tuffier’s Line (aka intercristal line)
Helps identify the correct spaces between vertebrae for inserting spinal anesthesia needles.

slide 20

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48
Q

In infants up to one year, what intervertebral space corresponds with the intercristal line (Tuffier’s line)?

A

L5-S1

slide 20

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49
Q

What ligament connects the lamina of S5?

A

sacrococcygeal ligament

slide 22

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50
Q

What is the access point for caudal anesthesia?

A

Sacral hiatus

slide 22

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51
Q

Where does the spinal cord begin (superiorly)?

A

Medulla oblongata

slide 23

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52
Q

What is the part of the spinal cord that tapers off (inferiorly)?

A

conus medularis

slide 23

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53
Q

What spinal level is the conus medularis in adults?

A

L1

some disagreement btw L1 or L2 or both, but for test its L1

slide 23

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54
Q

What spinal level is the conus medularis in infants?

A

L3

slide 23

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55
Q

What is the bundle of nerves that extends from the conus medularis to the end of the dural sac?

slide 23

A

cauda equina

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56
Q

What does the cauda equina consist of?

A

nerve roots from L2 to S5 vertebra and coccygeal nerve

slide 23

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57
Q

Where does the dural sac end in adults?

A

S2

slide 24

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58
Q

Where does the dural sac end in infants?

A

S3

slide 23

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59
Q

What is the filum terminale?

A

extension of the pia mater from the conus medullaris to the coccyx that anchors the spinal cord to the coccyx.

slide 24

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60
Q

What are the anatomical locations of the internal and external filum terminale?

A

Internal: conus medularis to the end of the dural sac (L1 to S2 in adults)

External: starts at dural sac and extends to the end of the sacrum (S2 to S5)

slide 24

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61
Q

Where does the anterior spinal artery originate from?

A

Vertebral artery

slide 25

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62
Q

What does the anterior vertebral artery supply?

A
  • Anterior 2/3 of the spinal cord
  • Motor portion (efferent/descending)

slide 25

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63
Q

Where do the two posterior spinal arteries originate and emerge from?

A

originate from vertebral artery, emerge from cranial vault

slide 25

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64
Q

What does the posterior spinal artery supply?

A
  • posterior
  • sensory portion (afferent/ascending)

slide 25

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65
Q

How do the anterior and posterior portions of the spinal cord protect it from ischemia?

A
  • posterior spinal arteries are paired and share collateral anastomotic links
  • anterior does not have as many links since it is one artery so motor function is more susceptible to ischemia.

slide 25

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66
Q

What spinal artery supplies the central area of the spinal cord?

A

the anterior spinal artery

slide 25

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67
Q

What is anterior spinal artery syndrome?

A

when the anterior spinal artery is affected by ischemia causing potential:
* motor paralysis
* loss of pain and temperature sensation BELOW the affected area

slide 26

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68
Q

What can cause ischemia of the spinal cord?

A
  • profound hypotension
  • mechanical blockage
  • blood vessel disease
  • bleeding/hemorrhage

slide 26

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69
Q

What additional branches of arteries can supply the anterior spinal artery?

A

branches of the intercostal and iliac arteries can supply additional blood flow to the anterior spinal artery however these are variable.

slide 26

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70
Q

What spinal level is the artery of Adamkiewicz?

A

T7-L2

Slide 26

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71
Q

What are the other two names for the artery of adamkiewicz?

A
  1. Great Radicular artery
  2. Great Anterior Medullary artery

Schmidt

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72
Q

What does the artery of adamkiewicz supply blood to?

A

Lower 2/3 of the spinal cord

very important, severing can cause anterior spinal artery syndrome

slide 26

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73
Q

Which spinal ligament runs along the back and connects the tips of the spinous processes?

A

supraspinous ligament

yellow

slide 27

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74
Q

Which spinal ligament is located between the spinous processes and provides stability for adjacent vertebra?

A

the interspinous or interspinal ligament

green

slide 27

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75
Q

Which spinal ligament forms the sidewalls of the space outside the spinal cord (epidural space)?

A

Ligamentum flavum

blue

slide 27

76
Q

Which spinal ligament runs the length of the spinal column and attaches to the front of the vertebral bodies?

A

anterior longitudinal ligament

orange

slide 27

77
Q

Which spinal ligament runs along the backside of the vertebral bodies inside the spinal column?

A

posterior longitudinal ligament

purple

slide 27

78
Q

What does the anterior longitudinal ligament also connect to besides the vertebral bodies?

A

the outer fibers of the intervertebral discs to provide further stability and bind the vertebra together.

slide 27

79
Q

What layers are traversed during a midline approach to a SAB?

A
  1. skin
  2. subQ fat
  3. supraspinous ligament
  4. interspinous ligament
  5. ligamentum flavum
  6. dura mater
  7. subdural (potential) space
  8. arachnoid amter
  9. subarachnoid space (CSF return here)

slide 28

80
Q

What layers of tissue are traversed during a paramedian approach for a SAB?

A
  1. skin
  2. subQ fat
  3. ligamentum flavum
  4. dura mater
  5. subdural (potential space)
  6. arachnoid mater
  7. subarachnoid space (CSF return)

slide 28

81
Q

Why would we use a paramedian approach over a midline approach?

A

When the interspinous ligament is calcified or the patient cannouc flex their spine

slide 28

82
Q

What positioning would we put the patient in for a paramedian approach?

A

sitting, lying on their side, or prone

slide 28

83
Q

What angle off of midline do we insert the needle for a paramedian approach?

A

15 degrees off midline and down (approx 1 cm.)

slide 28

84
Q

What angle do we insert the needle for a midline approach?

A

10 degrees angled up

slide 28

85
Q

What happens if we are too lateral for a paramedian approach?

A

We will miss the subarachnoid space

slide 28

86
Q

Where is the cranial border of the epidural space?

A

the foramen magnum

this is where the epidural space starts

slide 31

87
Q

Where is the caudal border of the epidural space?

A

at the bottom near the sacrococcygeal ligament

slide 31

88
Q

What is the anterior border of the epidural space?

A

the posterior longitudinal ligament

slide 31

89
Q

What are the lateral borders of the epidural space?

A

vertebral pedicles

slide 31

90
Q

What is the posterior border of the epidural space?

A

ligamentum flavum and the vertebral lamina

slide 31

91
Q

What tissues are contained inside the epidural space?

A

nerves, fatty tissue, lymphatics, and blood vessels

slide 32

92
Q

What can decrease the availability of drugs in the epidural space?

A

the fatty tissue

Bupivacaine would be absorbed more than lidocaine, fentanyl, or morphine

slide 32

93
Q

What are the epidural veins called?

A

Batson’s plexus

slide 32

94
Q

What is unique about batson’s plexus?

A

they are valveless

slide 32

95
Q

Under what conditions might Batson’s plexus be engorged and why is that significant?

A

Pregnancy and obesity

Because it increases the risk of injection into vasculature during needle procedures.

slide 32

96
Q

What is important to note about the size of the veins in Batson’s plexus?

A

they get bigger laterally

slide 32

97
Q

What is the Plica Mediana Dorsalis?

A

a band of connective tissue located between the ligamentum flavum and the dura mater.
*presence of this structure is controversial

slide 33

98
Q

What potential impact does the plica mediana dorsalis pose?

A

It may act as a barrier within the epidural space and affect how medications spread and may play a role in unilateral blocks

slide 33

99
Q

What can we do if our epidural is only providing a unilateral block?

A

better one side than not at all

  • talk to patients prior to placing epidural to explain the posibility of this happening
  • try adjusting position
  • try pulling catheter out slightly but remember we still want 3-5 cm in the epidural space.

not on a slide just discussed in class

100
Q

What does the subarachnoid space contain?

A

CSF, nerve roots, and the spinal cord itself

slide 34

101
Q

What characteristic sensation is felt as the needle goes through the dura mater?

A

pop

slide 34

102
Q

What is contained in the subdural space?

A

Nothing. Its a potential space between the dura and arachnoid mater.

slide 35

103
Q

What happens if anesthetic is inadvertently injected into the subdural space with epidural dosing vs spinal dosing?

A

epidural dosing: “high spinal effect” (the medication effects a larger area than intended)

spinal dosing: failed spinal block

slide 35

104
Q

Where do C1-C7 spinal nerves exit the spinal column?

A

above their corresponding vertebra

slide 37

105
Q

Where does C8 spinal nerve exit the spinal column?

A

below C7

slide 37

106
Q

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

A

below their corresponding vertebra

slide 37

107
Q

How are spinal nerves formed?

A

By joining the anterior (ventral) and posterior (dorsal) nerve roots together.

slide 37

108
Q

What information does the anterior (ventral) nerve root carry? From where to where?

A

carries motor and autonomic information from the spinal cord to the body

slide 37

109
Q

What information does the posterior (dorsal) nerve root carry? From where to where?

A

sensory information from the body back to the spinal cord

slide 37

110
Q

What is the definition of a dermatome?

A

an area of skin that recieves sensory nerves from a single spinal nerve root.

slide 38

111
Q

What dermatome level(s) supplies the anterior and inner surface of the lower limbs?

A

L1-L4

slide 39

112
Q

What dermatome level(s) supplies the foot?

A

L4, L5, S1

slide 39

113
Q

What dermatome level(s) supplies the medial side of the great toe?

A

L4

slide 39

114
Q

What dermatome level(s) supplies the posterior and outer surface of the lower limbs?

A

S1, S2, L5

slide 39

115
Q

What dermatome level(s) supplies the lateral margin of foot and little toe?

A

S1

slide 39

116
Q

What dermatome level(s) supplies the perineum?

A

S2, S3, S4

slide 39

117
Q

What dermatome level(s) supplies the level of the umbilicus?

A

T10

slide 39

118
Q

What dermatome level(s) supplies the inguinal or groin regions?

A

T12

slide 39

119
Q

What dermatome level(s) supplies the clavicles?

A

C5

slide 39

120
Q

What dermatome level(s) supplies the lateral parts of the upper limbs?

A

C5, C6, C7

slide 39

121
Q

What dermatome level(s) supplies the medial sides of the upper limbs?

A

C8, T1

slide 39

122
Q

What dermatome level(s) supplies the thumb?

A

C6

slide 39

123
Q

What dermatome level(s) supplies the hand?

A

C6, C7, C8

slide 39

124
Q

What dermatome level(s) supplies the ring and little fingers?

A

C8

slide 39

125
Q

What dermatome level(s) supplies the level of the nipples?

A

T4

slide 39

126
Q

What dermatome level(s) supplies the face?

A

Trick question. Face is supplied by cranial nerve 5 (V), not spinal nerves.

CN V = Trigeminal

slide 40

127
Q

What are the three branches of the trigeminal nerve?

A

V1: Opthalmic (forehead, scalp, upper eyelids)
V2: Maxillary (lower eyelids, cheeks, nostrils, upper lip, and upper teeth)
V3: Mandibular (lower jaw, lower teeth, lower lip, part of the tongue)

slide 40

128
Q

What is the desired dermatome level to block for peri-anal/anal surgery?

What is the other name for this type of block?

A

S2-S5

“saddle block”

slide 41

129
Q

What is the desired dermatome level to block for foot/ankle surgery?

A

L2

slide 41

130
Q

What is the desired dermatome level to block for thigh/lower leg/knee surgery?

A

L1

slide 41

131
Q

What is the desired dermatome level to block for vaginal delivery/uterine/hip procedure/tourniquet/TURP?

A

T10

slide 41

132
Q

What is the desired dermatome level to block for scrotum procedure?

A

S3

slide 41

133
Q

What is the desired dermatome level to block for penis procedure?

A

S2

slide 41

134
Q

What is the desired dermatome level to block for testicular procedure?

A

T8

testicles are embryonically derived from the same level as the kidneys for pain transmission (T10-L1)

slide 41

135
Q

What is the desired dermatome level to block for urologic/gynecologic/lower abdominal procedure?

A

T6

slide 41

136
Q

What is the desired dermatome level to block for c-section/upper abdominal procedures?

A

T4

sometimes may require concomitant general anesthesia due to vagal stimulation from abdominal traction

slide 41

137
Q

How does LA work when injected into the subarachnoid space?

A

LA acts on the myelinated preganglionic fibers of the spinal nerve roots. Inhibits neural transmission in the superficial layers of the spinal cord.

slide 43

138
Q

How does LA work when injected into the epidural space?

A

Diffusion and leakage.
Diffusion through the dural cuff to reach nerve roots.
Leakage through the intervertebral foramen into the paravertebral area (highlighted in green)

slide 43

139
Q

What is the MOST reliable factor affecting how far and wide the anesthetic speads when using hypo/isobaric solutions for SAB.

A

DOSE

slide 44

140
Q

For what solutions is the relative density of the anesthetic to CSF crucial in determining how is spreads?

A

Hyperbaric solutions

slide 44

141
Q

Low CSF volume correlates to ————- spread of LA in the intrathecal space.

A

increased or extensive

slide 44

142
Q

What factors decrease CSF volume which in turn requires less LA dose?

A

pregnancy, advanged age

143
Q

How do nerves change with advanced age?

A

They are more vulnerable to LA.

slide 44

144
Q

What are 4 controllable factors that affect the spread of LA for SAB?

A
  1. Baracity
  2. Patient Position
  3. Dose
  4. Site of injection

slide 44

145
Q

What are 3 non-controllable factors that affect the spread of LA for SAB?

A
  1. Volume of CSF
  2. Increased intra-abdominal pressure (obesity, pregnancy)
  3. Age (elderly)

slide 44

146
Q

What 5 factors DO NOT affect the spread of LA for SAB?

A
  1. Barbotage
  2. Speed of injection
  3. Orientation of bevel
  4. Addition of vasoconstrictor
  5. Gender

slide 44

147
Q

What are 3 controllable factors that significantly affect spread of LA with epidural injection?

A
  1. Local anesthetic volume (most important drug related factor)
  2. Level of injection (most important procedure related factor)
  3. Local anesthetic dose

slide 45

148
Q
A
149
Q

What are 2 controllabel factors that have a small effect on spead of LA when injected into the epidural space?

A
  1. Local Anesthetic concentration
  2. Patient position

slide 45

150
Q

What is 1 non-controllable factor that has a small effect on spread of LA when injected into the epidural space?

A

Patient height

Shorter stature may need less dose but this is controversial.

slide 45

151
Q

What 3 controllable factors do not affect spread of LA when injected into the epidural space?

A
  1. additives in the LA (might change onset, duration, or intensity but NOT spread)
  2. direction of the bevel of the needle
  3. speed of injection

slide 45

152
Q

If injected into the lumbar region of the epidural space, which direction will the LA spread?

A

mostly cephalad

slide 45

153
Q

If injected into the cervical region of the epidural space, which direction will the LA spread?

A

mostly caudad

slide 45

154
Q

If injected in the mid-thoracic region of the epidural space, which direction will LA spread?

A

equidistant both cephalad and caudad

slide 45

155
Q

What order are types of nerve fibers affected by LA?

A
  1. Pre-ganglionic ANS B fibers
  2. ANS and dorsal root C fibers
  3. A-gamma and A-delta fibers
  4. A-alpha and A-beta fibers

slide 46

156
Q

What function do A-alpha fibers have?

A

skeletal muscle movement and proprioception

slide 46

157
Q

What function do A-beta fibers have?

A

touch and pressure

slide 46

158
Q

What function do A-gamma fibers have?

A

skeletal muscle tone

slide 46

159
Q

What function do A-delta fibers have?

A

fast pain, temperature, and touch

slide 46

160
Q

What function dorsal root C fibers have?

A

slow pain, temperature, and touch

slide 46

161
Q

How is the sympathetic nervous system affected by LA when ANS B and C fibers are blocked?

A

decreased sympathetic tone

so we have decreased BP and HR

slide 47

162
Q

What is differential blockade?

A

refers to how different types of nerve fibers have varying sensitivities to local anesthetic which affects the level of block acheived

slide 47

163
Q

When does sensory blockade occur?

In reference to differential blockade?

A

At low enough concentrations of LA, which do not affect motor neurons.

This results in a higher block level compared to a motor block ie. why sensory occurs two levels about motor.

slide 47

164
Q

When does autonomic blockade occur?

In reference to differental blockade?

A

At even lower LA concentrations than sensory requires which leads to the highest level of blockade.

slide 47

165
Q

If sensory block occurs at T8, where will motor and autonomic block occur?

A

SNS block T2-T6
Motor block T10

slide 48

166
Q

At what level is the cardioaccelerator nerve?

A

T1-T4

Anytime the SNS block reaches this, we will see decreased HR and BP

slide 48

167
Q

In what order do the differential nerve fibers recovery from blockade?

A

Opposite order of block.

So motor blocks last and recovers first. SNS blocks first and recovers last.

slide 49

168
Q

What is our preferred method of assessing sensory block?

A

temperature

It is the first sense to be blocked. Second is pain, last is touch/pressure

slide 50

169
Q

What scale is used to monitor motor block?

A

The Modified Bromage Scale:

0: no motor block

1: slight motor block (cannot raise an extended leg but can move knees and feet)

2: moderate motor block (cannot raise an extended leg or move knees but can move the feet)

3: complete motor block (cannot move legs, knees, or feet)

slide 50

170
Q

What does the modified bromage scale specifically evaluate?

A

the function of lumbosacral nerves; does NOT assess movement above these regions

slide 50

171
Q

How is preload affected by neuraxial anesthesia?

A

Decreased.

Sympathectomy causes veins to dilate leading to blood pooling in the periphery and reducing the blood returned to the heart.

slide 51

172
Q

How is afterload affected by neuraxial anesthesia?

A

Decreased.

Sympathectomy partially dilates arterial circulation.

slide 51

173
Q

How much (%) is SVR affected by neuraxial anesthesia in a healthy patient?

A

about 15%

slide 51

174
Q

How much (%) is SVR affected by neuraxial anesthesia in an elderly or cardiac patient?

A

can decrease up to 25%

slide 51

175
Q

How is cardiac output affected by neuraxial anesthesia?

A

May initially increase then gradually decrease due to decrease in SVR and venous return leading to a reduced stroke volume

slide 51

176
Q

How is HR affected by neuraxial anesthesia?

A

Decreased due to blockade of cardiac accelerator fibers and activation of reflexes.

slide 51

177
Q

What reflexes cause bradycardia due to neuraxial anesthesia?

A

Bezold-Jarisch Reflex and Reverse Bainbridge Reflex

slide 51

178
Q

What is Bezold-Jarisch reflex?

A

Response to ventricular underfilling potentially leading to a significant bradycardia and asystole.

slide 51

179
Q

What receptors mediate the Bezold-Jarisch reflex? What medication reverses this reflex?

A

Mediated by 5-HT3 receptros in the vagus nerve and ventricular myocardium.

Reversed by Zofran.

slide 51

180
Q

What is the Reverse Bainbridge reflex?

A

triggered by reduced stretching of the heart’s right atrium.

Remember if we are fluid overloaded and the heart muscle stretches too much, the bainbridge kicks in to increase the heart rate and pump out more fluid.

slide 51

181
Q

How much does the reverse bainbridge reflex decrease HR?

A

by about 20 bpm

slide 51

182
Q

What happens if there is unopposed parasympathetic tone to the cardioaccelerator fibers caused by sympathetic block?

A

profound bradycardia, hypotension, and potentially sudden cardiac arrest.

This can be seen in young adults with high parasympathetic tone. It occurs in 7:10,000 SAB and 1:10,000 epidurals.

slide 52

183
Q

When does sudden cardiac arrest occur after neuraxial anesthesia?

A

20-60 minutes after onset of LA

slide 52

184
Q

What are 4 interventions to prevent spinal anesthesia induced hypotension?

A
  1. Vasopressors
  2. 5-HT3 Antogonists
  3. Fluid management
  4. Positioning

slide 53

185
Q

Which is better for preventing spinal anesthesia induced hypotension through fluid management: Co-loading or Pre-loading?

A

Co-loading
Administering IV fluids right after the spinal block rather than pre-block hydration to prevent drops in blood pressure

slide 53

186
Q

What is the dose of fluid we give for co-loading hydration for adults?

A

15 ml/kg

slide 53

187
Q
A

Principles of Anesthesia (2 decks)

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