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
- Arachnoid Mater
- Pia Mater
S29
2
Q
List the 3 key spaces discussed in class.
A
- Epidural space
- Subdural space
- Subarachnoid space
S30
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).
S30
4
Q
What is the subdural space?
A
- A potential space between the dura mater and the arachnoid mater.
S30
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.*
S30
6
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.
S30
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).
S31
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.
S31
9
Q
List the contents of the epidural space
A
Contains nerves, fatty tissue,lymphatics,and blood vessels.
S32
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
S32
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.
S32
If getting blood, then you are injecting laterally and not midline!
12
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.
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.
S33
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.
S34
15
Q
This space is the primary target when performing a spinal anesthetic procedure
A
Subarachnoid Space
S34
16
Q
What is the characteristic Sensation when performing a spinal anesthesia?
A
- “POP”
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)
S35
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
S35
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!!!)
S35
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)
S36
21
Q
T/F
the pia mater lacks vasculature
A
FALSE!
The pia mater is HIGHLY vascular
S36
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
S36
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
S37
24
Q
Where do the spinal nerves exit for thoracic, lumbar, sacral, and coccyx nerves?
A
below the vertebra they are named for
S37
25
Each spinal nerve is formed by the joining of what?
2 nerve roots:
Anterior (Motor) and Posterior (Sensory) nerve roots
| S37
26
What is a dermatome?
An area of skin that receives **sensory nerves** from a single spinal nerve root
| S38
27
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
| S38
28
L1,2,3,4 dermatomes cover
anterior and inner surface of the lower limbs
| S39
29
L4,5 S1 dermatomes cover
foot
| S39
30
L4 dermatome covers
medial side of great toe
| S39
31
S1,2 L5 dermatome covers
posterior and outer surface of lower limbs
| S39
32
S1 dermatome covers
Lateral margin of foot and little toe
| S39
33
S2,3,4 dermatome covers
Perineum
| S39
34
T10 dermatome covers
Umbilicus
| S39
35
T12 dermatome covers
Inguinal or groin regions
| S39
36
C5 dermatome covers
Clavicles
| S39
37
C5,6,7 dermatomes cover
lateral parts of upper limbs
| S39
38
C8, T1 dermatomes cover
Medial sides of upper limbs
| S39
39
C6 dermatome covers
Thumb
| S39
40
C6,7,8 dermatomes cover
Hand
| S39
41
C8 dermatome covers
Ring and little fingers
| S39
42
T4 dermatome covers
Nipples
| S39
43
Which Nerve transmits facial sensations? What are its branches?
Trigeminal Nerve (CN-V)
V1- opthalmic
V2- maxillary
V3- mandibular
| S40
44
what is the dermatome for peri-anal/anal surgery aka saddle block?
S2-S5
| slide 41
45
Desired dermatome for foot/ankle surgery?
L2
| slide 41
46
Desired dermatome for thigh/lower leg/knee surgery?
L1
| slide 41
47
Desired dermatome for vaginal delivery/uterine/hip procedure/ tourniquet/ TURP?
T10
| slide 41
48
Desired dermatome for scrotum surgery?
S3
| slide 41
49
Desired dermatome for penis surgery?
S2
| slide 41
50
Desired dermatome for testicular procedures?
T8
*testicles are embryonically derived from the same lavel as the kidneys for pain transmission [T10-L1]*
| slide 41
51
Desired dermatome for urologic/gynecologic/lower abdominal surgery?
T6
| sliide 41
52
Desired dermatome for ceseran section/upper abdominal surgery?
T4
*sometimes may require concomitant genreral anesthesia d/t vagal stimulation form abdominal traction*
| slide 41
53
For Epidurals to work effectively we need the LA to ___ through the dural cuff to reach the ___.
diffuse
Nerve Roots
| slide 43
54
what are controllable factors that affect the spread of spinals?
* Baricity
* Patient Position
* Dose
* Site of Injection
| slide 44
55
what are the non-controllable factors that affect the spread of spinals?
* Volume of CSF (Less CSF = Higher the blockade)
* Increased Intra-abdominal Pressure (obesity,pregnancy)
* Age (elderly)
| slide 44
56
what are the factors that dont affect the spread of spinals?
* Barbotage (repeated aspiration and reinjection of CSF)
* Speed of Injection
* Bevel orientation
* Addition of Vasoconstrictor
* Gender
| slide 44
57
what are the key points to remember for spinals?
* dose is crucial
* baracity matters
* low csf volume
* advanced age
* pregnanacy
| slide 44
58
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.
| slide 44
59
why is pregnancy an important factor to consider with spinals?
Decreased CSF volume due to increased intraabdominal pressure.
| slide 44
60
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
| slide 45
61
what are non-controllable factors that significantly affect the spread of epidurals
* Pregnancy
* Old Age
| slide 45
62
what are controllable factors that have small affect on the spread of epidurals
* Local Anesthetic Concentration
* Patient Position
| slide 45
63
what are non-controllable factors that have small affect on the spread of epidurals
height (Taller or shorter stature may slightly affect spread)
| slide 45
64
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
| slide 45
65
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
| slide 45
66
what are the 3 nerve fiber types?
A fibers
B fibers
C fibers
| slide 46
67
what are the different subtypes of A fibers?
* alpha
* beta
* gamma
* delta
| slide 46
68
Which nerve fiber has the largest diameter and which one has the smallest?
* largest: A-alpha
* smallest: C fibers
| slide 46
69
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
| slide 46
## Footnote
This is also how they are arranged!!
70
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.
| slide 47
71
Between sensory and autonomic blockade, which requires less concentration of LA?
Which one results in the highest level of blockade?
Autonomic and Autonomic
| slide 47
72
In the Differential Blockade Zones:
* The ____ is 2 levels higher than the motor level
* The sympathetic level is ___-___ levels higher than the sensory level
Sensory level
2-6
| slide 48
73
* What two sensory aspects travel together?
* temperature and pain
| slide 48 talking
74
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
75
Recovery of Nerve blockade sequence
1. A-alpha, Beta, Gamma
2. C and A-delta
3. B fibers
| slide 49
76
Which nerve fibers are blocked the longest?
B fibers - they are the first on, and last off
| question in lecture
77
Order in which senses are blocked.
* 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
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)
| slide 50
79
The Modified Bromage Scale specifically evaluates what?
the function of lumbosacral nerves
| Slide 50
80
Why does preload decrease when performing neuraxial anesthesia?
Preload will decrease because of **sympathectomy** (venous dilation which pools blood in periphery and decreases venous return)
| slide 51
81
CV effects of neuraxial anesthesia: Afterload
* how much does SVR decrease in healthy vs Elderly/cardiac pts?
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
Why does C.O. decrease when performing neuraxial anesthesia?
decrease in venous return and SVR
| slide 51
83
Why does heart rate decrease in neuraxial anesthesia?
* blockade of cardiac accelerator fibers (T1-T4) blocks SNS tone
* Activation of reflexes:
1. Benzold-Jarish Reflex
2. Reverse bainbridge reflex
| slide 51
84
The Bezold-Jarisch Reflex is a response caused by ___ which could lead to ___.
ventricular underfilling
significant bradycardia
| slide 51
85
The Bezold-Jarisch reflex is mediated by ___ receptors, located in the ___ nerve and the ___.
5-HT3
Vagus
Ventricular myocardium
86
What triggers the Reverse Bainbridge reflex
reduced stretching of the RA
| slide 51
87
What population is more likely to have sudden cardiac arrest?
How often is sudden cardiac arrest seen after spinals/epidurals?
* Can be seen young adults with high parasympathetic tone
* 7:10,000 spinals
* 1:10,000 epidurals
| slide 52
88
How long after a neuraxial block is given would you see a cardiac arrest?
* 20-60 min after onset of spinal
| slide 52
89
Prevention of spinal-anesthesia induces HoTN: prevention with drugs (2 drugs)
* Vasopressors: **phenylephrine**
* 5-HT3 Antagonists: **ondansetron**
| slide 53
90
Fluid Management methods to prevent spinal-anesthesia induced hypotension:
* Co-loading
* Avoid Preloading
* Avoid Excess Fluids
| slide 53
91
Describe "Co-loading"
Administering intravenous fluids (around 15 mL/kg) right after the spinal block to prevent drops in blood pressure.
92
Drug Treatment of spinal-anesthesia induced HoTN:
* Vasopressors: **ephedrine**, **epinephrine**, **phenylephrine**
* Anticholinergics: Atropine (rarely = lasts too long)
| slide 54
93
Why do we want to be cautious when doing position changes for Treatment of Spinal-Anesthesia Induced Hypotension?
> 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
True or False:
Pulmonary Effects from neuraxial anesthesia are usually minimal.
TRUE
95
These two flow-volume loop measurements are DECREASED after neuraxial anesthesia
ERV
VC
96
Where are our Phrenic nerves? (Dermatomes)
C3-C5
97
# GI System effects with Neuraxial Anesthesia
Parasympathetic innervation is primarily via the ___.
Sympathetic innervation of GI tract stems from ___.
Vagus Nerve
T5-L2
98
What are the impacts of neuraxial anesthesia on the GI system?
Reduces Sympathetic tone
Increases Parasympathetic activity
99
Sympathetic blockade above ___ affects bladder control.
T10
100
# Systemic Effects of Neuraxial Anesthesia on the Genitourinary system
The addition of neuraxial opioids will cause what 2 things?
Decrease in detrusor contraction
Increase in bladder capacitance
101
True or False:
Foley catheters are not required for neuraxial anesthesia cases.
FALSE
