Exam 1 Spinal & Epidural Neuraxial Anesthesia [5/30/24] Flashcards
1
Q
What is the order of the meningeal layers from outter to inner?
A
- Dura Mater:The outer most layer.
- Arachnoid Mater:The middle layer.
- Pia Mater:The inner most layer that directly covers the SC.
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2
Q
Spinal Anesthesia is also called?
A
- Subarachnoid block
- Intrathecal
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3
Q
List the 3 key spaces discussed in class.
A
- Epidural space
- Subdural space
- Subarachnoid space
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4
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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5
Q
What is the subdural space?
A
- A potential space between the dura mater and the arachnoid mater.
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6
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), which cushions and protects the spinal cord
- This is where we want the tip of the needle for spinal anesthesia.
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7
Q
What 2 things might happen if the subdural space is hit?
A
- if its spinal it wont work
- if its epidural, will have high spinal block.
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8
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: At the top,near the base of the skull (foramen magnum).
- Caudal Border:At the bottom,near the ligament connected to the coccyx (sacrococcygeal ligament).
- Anterior Border:In front,lined by the posterior longitudinal ligament along the vertebrae.
- Lateral Borders:On the sides,marked by the bony projections of the vertebrae (vertebral pedicles).
- Posterior Borders:At the back,framed by ligamentum flavum and the bony plates of the vertebrae (vertebral lamina).
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9
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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10
Q
- what is in front of the epidural space?
- what is the posterior border of epidural space?
A
- Posterior ligament
- then we have the body of the vertebra and then the anterior ligament.
- the anterior portion of the epidural space is one of the ligaments that we dont want to touch [this is the posterior ligament]
- Ligamentum flavum and vertebral lamina
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11
Q
List the contents of the epidural space
A
Contains:
* nerves
* fatty tissue
* lymphatics
* blood vessels
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12
Q
What is the role of the contents of the epidural space?
A
- Aids in drug absorption.
- Fatty tissue in this area can absorb and decrease the availability of certain drug
- Ex: bupivacaine is absorbed more than lidocaine or fentanyl or morphine
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13
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!
14
Q
Plica Mediana Dorsalis
- Plica Mediana Dorsalis is for spinals or epidurals?
- What is it?
- What is its impact?
A
- Epidurals only.
- Thought to be a band of connective tissue located between the ligamentum flavum and the dura mater
- 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.
15
Q
What is the clinical relevance of Plica Mediana Dorsalis
A
- Catheter Insertion: The plica mediana dorsalis is sometimes considered a possible reason for complications in placing an epidural catheter.
- 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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16
Q
How much catheter should be left in the epidural space?
A
3-5cm
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17
Q
If giving sufentanyl to a laboring mother, take caution becuase?
A
It travels and crosses the placenta resulting in low APGAR scores.
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18
Q
What can we do for one sided blocks?
A
- Positioning
- Pull the catheter out a little. Be cautious that the catheter is still in the epidural space.
- Pull out and start over again.
- Talk to the pts about this in informed consent.
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19
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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20
Q
This space is the primary target when performing a spinal anesthetic procedure
A
Subarachnoid Space
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21
Q
If the needle is advanced too far anteriorly when doing spinals what are possible layers that are passed
A
- pia mater
- spinal cord
- the posterior longitudinal ligament before reaching bone.
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22
Q
What are the characteristic Sensation when performing a spinal anesthesia.
A
- During spinal anesthesia, a characteristic “pop” is often felt when the needle passes through the outer membrane, the dura mater.
23
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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24
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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25
If we inadvertently place a spinal dose in the subdural space what would the result be?
failed spinal block
(it wont work!!!)
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26
The Dura mater extends from ____ to ____ .
Foramen magnum to the dural sac (which ends at S2 in adults and S3 in infants)
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27
Which layer of meninges is the 1st layer encountered by the needle after advancnig through the epidural space?
Dura Mater
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28
What type of tissue makes up the arachonid mater?
connective tissue
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29
T/F
the pia mater lacks vasculature
FALSE!
The pia mater is HIGHLY vascular
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30
Where is the pia mater located?
Should the spinal needle punture this layer of meninges?
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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31
How mant spinal nerves do we have total? at each level of the spinal cord?
31 spinal nerves!
C-8
T-12
L-5
S-5
Coccyx-1
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32
Which of the cervical spine nerves is an exception in terms of where it exits the vertebra?
C8 nerve exits BELOW C7 whereas all other cervical spine nerves exit above the vertebra they are named for.
33
Where do the spinal nerves exit for thoracic, lumbar, sacral, and coccyx nerves?
below the vertebra they are named for
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34
Each spinal nerve is formed by the joining of what?
2 nerve roots:
* **Anterior/ventral nerve root** (which carries motor and autonomic information from the SC to the body)
and
* **Posterior/dorsal nerve root** (which carries sensory information from the body to the SC)
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35
What is a dermatome?
An area of skin that receives sensory nerves from a single spinal nerve root
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36
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
TRUE
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37
The umbilicus looks like it should be served by the ____ nerve, but its actually served by ____
L3
T10 (actual)
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L1,2,3,4 dermatomes cover
anterior and inner surface of the lower limbs
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L4,5 S1 dermatomes cover
foot
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L4 dermatome covers
medial side of great toe
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41
S1,2 L5 dermatome covers
posterior and outer surface of lower limbs
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S1 dermatome covers
Lateral margin of foot and little toe
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43
S2,3,4 dermatome covers
Perineum
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44
T10 dermatome covers
Umbilicus
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45
T12 dermatome covers
Inguinal or groin regions
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C5 dermatome covers
Clavicles
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C5,6,7 dermatomes cover
lateral parts of upper limbs
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C8, T1 dermatomes cover
Medial sides of upper limbs
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C6 dermatome covers
Thumb
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C6,7,8 dermatomes cover
Hand
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C8 dermatome covers
Ring and little fingers
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T4 dermatome covers
Nipples
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53
T/F
Sensory information from the face is not conducted by spinal nerves
True!
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54
Which Nerve transmits facial sensations? What are its branches?
* Trigeminal Nerve (CNV)
* **V1- opthalmic** [forehead scalp, and upper eyelids]
* **V2- maxillary** [lower eyelids, cheeks, nostrils, upper lip, upper teeth]
* **V3- mandibular** [lower jaw, lower teeth, lower lip, and part of tongue]
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55
Chart of branches of the trigeminal nerve with course and function
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## Footnote
He did not address this chart as much as he did previous information on the same slide
56
what is the dermatone for peri-anal/analsurger aka saddle block?
S2-S5
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57
what is the dermatone for foot/ankle surgery?
L2
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58
what is the dermatone for thigh/lower leg/knee surgery?
L1
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59
what is the dermatone for vaginal delivery/uterine/hip procedure/ tourniquet/ TURP?
T10
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60
what is the dermatone for scrotum surgery?
S3
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61
what is the dermatone for penis surgery?
S2
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62
what is the dermatone for testicular procdures?
T8
*testicles are embryonically derived from the same lavel as the kidneys for pain transmission [T10-L1]*
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63
what is the dermatone for urologic/gynecologic/lower abdominal surgery?
T6
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what is the dermatone for ceseran section/upper abdominal surgery?
T4
*sometimes may require concomitant genreral anesthesia d/t vagal stimulation form abdominal traction*
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65
For Spinals:
* location
* target
* Location: Subarachnoid space of the spinal cord.
* Target: LA acts on the myelinated preganglionic fibers of the spinal nerve roots
* *Also, inhibits neural transmission in the superficial layers of the spinal cord.*
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For Epidurals:
* Location
* Process
* Location: In the epidural space outside the dura mater.
* Process:
* Diffusion: LA diffuse through the dural cuff to reach nerve roots.
* Leakage: LA can leak through the intervertebral foramen into the paravertebral area (highlighted in green).
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67
The spread of local anesthetic in the spinal or epidural space determines what?
the block height
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68
what are controllable factors that affect the spread of spinals?
* Baricity
* Patient Position
* Dose
* Site of Injection
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69
what are the non-controllable factors that affect the spread of spinals?
* Volume of CSF
* Increased Intra-abdominal Pressure (obesity,pregnancy)
* Age (elderly)
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70
what are the factors that dont affect the spread of spinals?
* Barbotage (repeated aspiration and reinjection of CSF)
* Speed of Injection
* Orientation of Bevel
* Addition of Vasoconstrictor
* Gender
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71
what are the key points to remeber for spinals?
* dose is crucial
* baracity matters
* low csf volume
* advanced age
* pregnanacy
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72
why is dosing crucial for spinals?
It's the most reliable factor affecting how far and wide the anesthetic spreads when using a hypo- or isobaric solution.
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73
why does baracity matter in spinals?
For hyperbaric solutions, the relative density of the anesthetic to CSF is crucial in determining how it spreads.
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74
why does low CSF volume matter in spinals?
Low CSF volume correlates to extensive spread of LA in intrathecal space
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75
why is advanced age important factor to consider with spinals?
With advanced age, neural nerves are vulnerable to LA and CSF volume decreases.
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76
why is pregnancy an important factor to consider with spinals?
Decreased CSF volume due to increased intraabdominal pressure.
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77
what are controllable factors that **significantly affect** the spread of epidurals
* **Local Anesthetic Volume**: Most important drug related factor
* **Level of injection**: Most important procedure related factor
* **Local Anesthetic dose**
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78
what are **non-controllable factors that significantly affect** the spread of epidurals
* Pregnancy
* Old Age
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79
what are **controllable factors that have small affect** on the spread of epidurals
* Local Anesthetic Concentration
* Patient Position
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80
what are **non-controllable factors that have small affect** on the spread of epidurals
* **Height** (Taller or shorter stature may slightly affect spread)
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81
what are controllable factors that have no affect on the spread of epidurals
* Additives in the Anesthetic (Might change onset time or duration but not spread.)
* Direction of the Bevel of the Needle
* Speed of Injection
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82
Injection Levels and Spread Dynamics:
* Lumbar Region:
* Mid Thoracic Region:
* Cervical Region:
* Lumbar Region: mostly spreads cephalad.
* Mid-Thoracic Region: Spread is balanced both cephalad and caudad.
* Cervical Region: spreads caudad
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83
what are the 3 nerve fiber types?
* A fibers
* B fibers
* C fibers
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84
what are the different subtypes of A fibers?
* alpha
* beta
* gamma
* delta
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85
for A-alpha fibers:
* mylenation
* function
* diameter
* block onset
* mylenation: heavy
* function: skeletal muscle-motor | proprioception
* diameter: 12-20
* block onset: 4th
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for A-beta fibers:
* mylenation
* function
* diameter
* block onset
* mylenation: heavy
* function: touch and pressure
* diameter: 5-12
* block onset: 4th
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for A-gamma fibers:
* mylenation
* function
* diameter
* block onset
* mylenation: medium
* function: skeletal muscle tone
* diameter: 3-6
* block onset: third
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for A-delta fibers:
* mylenation
* function
* diameter
* block onset
* mylenation: medium
* function: fast pain, temperature, touch
* diameter: 2-5
* block onset: 3rd
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for B fibers:
* mylenation
* function
* diameter
* block onset
* mylenation: light
* function: preganglionic ANS fibers
* diameter: 3
* block onset: first
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90
what are the 2 subtypes of C fibers?
sympathetic and dorsal root
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91
for C-sympathetic fibers:
* mylenation
* function
* diameter
* block onset
* mylenation: none
* function: postganglionic ANS fibers
* diameter: 0.3-1.3
* block onset: second
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for C-dorsal root fibers:
* mylenation
* function
* diameter
* block onset
* mylenation: none
* function: slow pain, temperature, touch
* diameter: 0.4-1.2
* block onset: second
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93
Which nerve fiber has the largest diamerter and which one has the smallest?
* largest: A-alpha
* smallest: C fibers
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94
how are the nerve fibers blocked? [first to last?]
* 1st: B fibers
* 2nd: C fibers
* 3rd: A-gamma and A-delta
* 4th: A-alpha and A-beta
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95
what is differential blockade?
Differential blockade refers to how different types of nerve fibers have varying sensitivities to local anesthetics, affecting the level of block achieved.
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96
what is sensory blockade?
Occurs at lower concentrations of LA, which do not affect motor neurons. This results in a higher block level compared to motor block.
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97
what is autonomic blockade?
Requires even lower concentrations of LA, affecting neither sensory nor motor neurons, leading to the highest level of blockade.
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98
what is the arrangement of nerves in a nerve bundle when introducing a local anesthetic?
* B= autonomic preganglionic fibers ( venodilation-hypotension)
* C= pain and temperature
* A-delta = pain and temperature
* A-gamma = motor tone
* A- beta = touch and pressure
* A - alpha = motor and proprioception
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99
In the Differential Blockade Zones:
* The ____ is 2 levels higher than the motor level
* The sympathetic level is ___-___ levels higher than the sensory level
* The **Sensory level** is 2 levels higher than the motor level
* The sympathetic level is **2-6** levels higher than the sensory level
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100
* What two sensory aspects travel together?
* which one should you test to see if your block is working?
* temperature and pain travel together
* use temperature like a cold spoon or alcohol swab to dtermine if your block is working
| slide 48 talking
101
Onset of nerve blockade sequence
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
102
Offset of Nerve blockade sequence
1. A-alpha, Beta, Gamma
2. C and A-delta
3. B fibers
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103
Which nerve fibers are blocked the longest?
B fibers - they are the first on, and last off
| question in lecture
104
How to monitor Sensory block?
* Temperature - this is the first sense to be blocked
* Pain - second sense to be blocked, assessed using a pinprick
* Touch/Pressure - last sense to be blocked, assessed with light touch
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105
How to monitor Motor block? and what is this monitoring scale called?
* **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)
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106
The Modified Bromage Scale specifically evaluates what?
the function of lumbosacral nerves, which are the lower spine and sacral nerve areas, and does not assess movement above these regions.
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107
CV effects of neuraxial anesthesia: Preload
Preload will decrease because of sympathectomy (venous dilation pools blood in periphery and decreases venous return)
T1-T4 block
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108
CV effects of neuraxial anesthesia: Afterload
* how much does SVR decrease?
Afterload decreases - sympathectomy partially dialates the arterial circulation
* Healthy pts: SVR decreases by ~15%
* Elderly or cardiac pts: SVR can decrease up to ~25%
| slide 51
109
CV effects of neuraxial anesthesia: Cardiac Output
CO may initially increase then decrease overtime because of blood vessle dilation
* a decrease in venous return and SVR leads to reduced SV and CO
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110
CV effects of neuraxial anesthesia: heart rate
Heart rate will decrease because of:
* blockade of cardiac accelerator fibers (T1-T4) blocks SNS tone
* Activation of reflexes: Benzold-Jarish Reflex, reverse bainbridge reflex
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111
Bezold-Jarisch Reflex
* Response to ventricular underfilling, potentially leading to a significant **bradycardia and asystole.**
* Bezold-Jarisch Reflex is mediated by 5-HT3 receptors in the vagus nerve and ventricular myocardium
* Ondansetron is a good 5HT3 recptor antagonist
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112
Reverse Bainbridge reflex
Reverse Bainbridge Reflex: Triggered by reduced stretching of heart's right atrium.
| slide 51
113
Sudden cardiac arrest: Unopposed ____ ____ to the cardioaccelerator fibers can result in profound bradycardia, hypotension, and sudden cardiac arrest.
Unopposed **parasympathetic tone** to the cardioaccelerator fibers can result in profound bradycardia, hypotension, and sudden cardiac arrest.
| Slide 52
114
* What population is more likely to have sudden cardiac arrest?
* how often is sudden cardiac arrest after a spinal seen?
* how often is sudden cardiac arrest after an epidural seen?
* Can be seen young adults with high parasympathetic tone
* 7:10,000 spinals
* 1:10,000 epidurals
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115
* How long after a neuraxial block is given would you see a cardiac arrest?
* what are the arrests associated with?
* 20-60 min after onset of spinal
* Associated with large blood loss and orthopedic cement placement
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116
What 2 drug classes can be used for prevention of spinal-anesthesia induced HoTN?
* **Vasopressors**: Medications like **phenylephrine** help maintain blood pressure by constricting blood vessels.
* **5-HT3 Antagonists**: Drugs like **ondansetron** can mitigate reflexes that cause hypotension, such as the Bezold-Jarisch reflex mediated by the vagus nerve.
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117
* What kind of fluid management is best at prevention of spinal-anesthesia induces HoTN?
* What two things do we want to avoid?
* Co-loading: Administering intravenous fluids (around 15 mL/kg) right after the spinal block to prevent drops in blood pressure.
* Avoid Preloading: **Pre-block hydration is not routinely recommended due to minimal impact on preventing hypotension.**
* Avoid Excess Fluids: Excessive fluid can overload the circulatory system, especially in patients with heart problems.
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118
What non-pharmacological interventions can help with prevention of spinal-anesthesia induced HoTN?
Positioning: Adjusting the patient’s position, like slight pelvic tilting, to optimize blood flow and reduce risks.
| slide 53
119
What 2 drug classes are used for treatment of spinal-anesthesia induced HoTN?
* Vasopressors: Such as **ephedrine** and **epinephrine** and **phenelphrine** are used based on the patient’s heart rate and symptoms. Ephedrine is preferred if there is symptomatic bradycardia.
* Anticholinergics: Atropine may be used if the patient is experiencing bradycardia.
*(according to Tito, atropine is rarely used because it lasts long after the procedure)*
| slide 54
120
What fluids are used for treatment of spinal-anesthesia induced HoTN?
Fluids: Crystalloids or colloids to maintain adequate blood volume.
* safe to use crystalloid first then colloids later:
* concern with colloids: cost, binds to drugs, and **renal problems** (increases blood viscosity and can lead to renal problems)
| slide 54 and talking in lecture
121
What patient positions should be used with caution for treatment of spinal-anesthesia induced HoTN?
Position Caution:
* Trendelenburg Position: This involves tilting the bed to increase venous return, but using a > 20-degree tilt can reduce cerebral perfusion because the tilt can reduce venous brain drainage. *make sure we are not using a hyperbaric LA*
* Position Influence on Block Effectiveness: If the block is not set yet, the block height can increase due to gravity
| slide 54
