Neuraxial (Exam 1) Flashcards
1
Q
What type of neuraxial anesthesia is pediatric specific?
A
Caudal
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
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
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
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
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
7
Q
What are 4 relative contraindications to neuraxial anesthesia?
A
- deformities of the spinal column (kypho, lordo, scoliosis)
- pre-existing diseases of the spinal cord (MS, post-polio syndrome)
- Chronic headache/backache
- Inability to perform SAB/epidural after 3 attempts
Slide 8
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
9
Q
What are 8 absolute contraindications to neuraxial anesthesia?
A
- Coagulopathy (risk of epidural hematoma)
- Pt refusal
- Evidence of dermal site infection
- Severe or critical valvular heart disease
- HSS (Idiopathic hypertrophic subaortic stenosis)
- Surgery lasting longer than the duration of the anesthetic
- Increased ICP
- Severe CHF
Slide 9 & 10
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
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
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
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
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
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
16
Q
What is normal plt levels?
A
150,000 - 300,000
slide 9
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
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
19
Q
What valve size is considered severe aortic stenosis and mitral stenosis?
A
AS ≤ 1.0 cm2
MS < 1.0 cm2
slide 10
20
Q
What is the clinical triad of aortic stenosis and the life expectancy at each stage?
A
- Angina (5 yrs)
- Syncope (3 yrs)
- Failure and SOB (2 yrs)
slide 10
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
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
23
Q
What is the onset comparison between spinal vs. epidural?
A
Spinal: rapid (about 5 minutes)
Epidural: slow (10-15 minutes)
slide 11
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
25
What is the nature of block comparison between spinal vs. epidural?
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)
## Footnote
slide 11
26
What is the motor block comparison between spinal vs. epidural?
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)
## Footnote
slide 11
27
What is the hypotension comparison between spinal vs. epidural?
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*
## Footnote
slide 11
28
What is the duration comparison between spinal and epidural?
Spinal: limited and fixed (inject medication and then d/c access)
Epidural: unlimited (catheter stays in place)
## Footnote
slide 12
29
What is the placement level comparison between spinal and epidural?
Spinal: L3-L4 (bigger space), L4-L5 (safest for learning), L5-S1
Epidural: any spinal level
## Footnote
slide 12
30
How do we dose spinal vs epidural?
Spinal: dose based (mg)
Epidural: volume based (ml)
## Footnote
slide 12
31
Is spinal or epidural more difficult according to slide 12 table?
epidural requires more skill
## Footnote
slide 12
32
Which neuraxial poses a risk for LA toxicity?
only epidural
*subarachnoid blocks require such small doses to acheive block, we dont have a risk for toxicity*
## Footnote
slide 12
33
How does gravity influence spinal vs. epidural?
spinal: influenced by baricity (whether the drug sinks or floats)
epidural: influenced by patient position
## Footnote
slide 12
34
How many vertebra do we have and what is the split?
33 total
7 cervical
12 thoracic
5 lumbar
5 sacral (fused)
4 coccyx (fused)
## Footnote
slide 13
35
What is the ligament connecting the sacrum to the coccyx?
sacrococcygeal ligament
## Footnote
slide 14
36
What are the two main structures of vertebra?
body (anterior) and vertebral arch (posterior)
## Footnote
slide 15
37
What two structures link the anterior and posterior segments of the vertebral arch?
lamina (posterior) and pedicle (anterior)
## Footnote
slide 15
38
What is housed in the vertebral foramen created by the vertebral arches of the vertebra?
spinal cord, nerve roots, epidural space
## Footnote
slide 15
39
What are the processes that come off of the vertebral arch?
transverse processes (lateral)
spinous processes (posterior midline)
## Footnote
slide 16
40
How are the lumbar vertebrae different from the cervical and throacic?
The angle of the spinous processes is greater allowing for easer needle access.
## Footnote
slide 17
41
What is the landmark where the spinal nerves exit the spine?
intervertebral foramina
## Footnote
slide 18
42
What forms the facet joints of vertebra?
the inferior articular process of the superior vertebra and the superior articular process of the inferior vertebra
## Footnote
slide 19
43
What do the facet joints do?
guide and limit spines movement
## Footnote
slide 19
44
What happens if the facet joint suffers an injury impact?
It can press on nearby spinal nerves. That pressure can cause pain and muscle spasms in that spinal nerves dermatome.
## Footnote
slide 19
45
What level of the spine is the superior aspect of the iliac crest?
L4
## Footnote
slide 20
46
What level of the spine is the posterior superior iliac spine?
S2
## Footnote
slide 20
47
What is the line called that relates to the superior iliac crest being the same level as L4?
Tuffier's Line (aka intercristal line)
Helps identify the correct spaces between vertebrae for inserting spinal anesthesia needles.
## Footnote
slide 20
48
In infants up to one year, what intervertebral space corresponds with the intercristal line (Tuffier's line)?
L5-S1
## Footnote
slide 20
49
What ligament connects the lamina of S5?
sacrococcygeal ligament
## Footnote
slide 22
50
What is the access point for caudal anesthesia?
Sacral hiatus
## Footnote
slide 22
51
Where does the spinal cord begin (superiorly)?
Medulla oblongata
## Footnote
slide 23
52
What is the part of the spinal cord that tapers off (inferiorly)?
conus medularis
## Footnote
slide 23
53
What spinal level is the conus medularis in adults?
L1
| some disagreement btw L1 or L2 or both, but for test its L1
## Footnote
slide 23
54
What spinal level is the conus medularis in infants?
L3
## Footnote
slide 23
55
What is the bundle of nerves that extends from the conus medularis to the end of the dural sac?
## Footnote
slide 23
cauda equina
56
What does the cauda equina consist of?
nerve roots from L2 to S5 vertebra and coccygeal nerve
## Footnote
slide 23
57
Where does the dural sac end in adults?
S2
## Footnote
slide 24
58
Where does the dural sac end in infants?
S3
## Footnote
slide 23
59
What is the filum terminale?
extension of the pia mater from the conus medullaris to the coccyx that anchors the spinal cord to the coccyx.
## Footnote
slide 24
60
What are the anatomical locations of the internal and external filum terminale?
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)
## Footnote
slide 24
61
Where does the anterior spinal artery originate from?
Vertebral artery
## Footnote
slide 25
62
What does the anterior vertebral artery supply?
* Anterior 2/3 of the spinal cord
* Motor portion (efferent/descending)
## Footnote
slide 25
63
Where do the two posterior spinal arteries originate and emerge from?
originate from vertebral artery, emerge from cranial vault
## Footnote
slide 25
64
What does the posterior spinal artery supply?
* posterior
* sensory portion (afferent/ascending)
## Footnote
slide 25
65
How do the anterior and posterior portions of the spinal cord protect it from ischemia?
* 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.
## Footnote
slide 25
66
What spinal artery supplies the central area of the spinal cord?
the anterior spinal artery
## Footnote
slide 25
67
What is anterior spinal artery syndrome?
when the anterior spinal artery is affected by ischemia causing potential:
* motor paralysis
* loss of pain and temperature sensation BELOW the affected area
## Footnote
slide 26
68
What can cause ischemia of the spinal cord?
* profound hypotension
* mechanical blockage
* blood vessel disease
* bleeding/hemorrhage
## Footnote
slide 26
69
What additional branches of arteries can supply the anterior spinal artery?
branches of the **intercostal and iliac arteries** can supply additional blood flow to the anterior spinal artery however these are variable.
## Footnote
slide 26
70
What spinal level is the artery of Adamkiewicz?
T7-L2
## Footnote
Slide 26
71
What are the other two names for the artery of adamkiewicz?
1. Great Radicular artery
2. Great Anterior Medullary artery
## Footnote
Schmidt
72
What does the artery of adamkiewicz supply blood to?
Lower 2/3 of the spinal cord
**very important, severing can cause anterior spinal artery syndrome**
## Footnote
slide 26
73
Which spinal ligament runs along the back and connects the tips of the spinous processes?
supraspinous ligament
## Footnote
slide 27
74
Which spinal ligament is located between the spinous processes and provides stability for adjacent vertebra?
the interspinous or interspinal ligament
## Footnote
slide 27
75
Which spinal ligament forms the sidewalls of the space outside the spinal cord (epidural space)?
Ligamentum flavum
## Footnote
slide 27
76
Which spinal ligament runs the length of the spinal column and attaches to the front of the vertebral bodies?
anterior longitudinal ligament
## Footnote
slide 27
77
Which spinal ligament runs along the backside of the vertebral bodies inside the spinal column?
posterior longitudinal ligament
## Footnote
slide 27
78
What does the anterior longitudinal ligament also connect to besides the vertebral bodies?
the outer fibers of the intervertebral discs to provide further stability and bind the vertebra together.
## Footnote
slide 27
79
What layers are traversed during a midline approach to a SAB?
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)
## Footnote
slide 28
80
What layers of tissue are traversed during a paramedian approach for a SAB?
1. skin
2. subQ fat
3. ligamentum flavum
4. dura mater
5. subdural (potential space)
6. arachnoid mater
7. subarachnoid space (CSF return)
## Footnote
slide 28
81
Why would we use a paramedian approach over a midline approach?
When the interspinous ligament is calcified or the patient cannouc flex their spine
## Footnote
slide 28
82
What positioning would we put the patient in for a paramedian approach?
sitting, lying on their side, or prone
## Footnote
slide 28
83
What angle off of midline do we insert the needle for a paramedian approach?
15 degrees off midline and down (approx 1 cm.)
## Footnote
slide 28
84
What angle do we insert the needle for a midline approach?
10 degrees angled up
## Footnote
slide 28
85
What happens if we are too lateral for a paramedian approach?
We will miss the subarachnoid space
## Footnote
slide 28
86
Where is the cranial border of the epidural space?
the foramen magnum
| this is where the epidural space starts
## Footnote
slide 31
87
Where is the caudal border of the epidural space?
at the bottom near the sacrococcygeal ligament
## Footnote
slide 31
88
What is the anterior border of the epidural space?
the posterior longitudinal ligament
## Footnote
slide 31
89
What are the lateral borders of the epidural space?
vertebral pedicles
## Footnote
slide 31
90
What is the posterior border of the epidural space?
ligamentum flavum and the vertebral lamina
## Footnote
slide 31
91
What tissues are contained inside the epidural space?
nerves, fatty tissue, lymphatics, and blood vessels
## Footnote
slide 32
92
What can decrease the availability of drugs in the epidural space?
the fatty tissue
| Bupivacaine would be absorbed more than lidocaine, fentanyl, or morphine
## Footnote
slide 32
93
What are the epidural veins called?
Batson's plexus
## Footnote
slide 32
94
What is unique about batson's plexus?
they are valveless
## Footnote
slide 32
95
Under what conditions might Batson's plexus be engorged and why is that significant?
Pregnancy and obesity
Because it increases the risk of injection into vasculature during needle procedures.
## Footnote
slide 32
96
What is important to note about the size of the veins in Batson's plexus?
they get bigger laterally
## Footnote
slide 32
97
What is the Plica Mediana Dorsalis?
a band of connective tissue located between the ligamentum flavum and the dura mater.
*presence of this structure is controversial
## Footnote
slide 33
98
What potential impact does the plica mediana dorsalis pose?
It may act as a barrier within the epidural space and affect how medications spread and may play a role in unilateral blocks
## Footnote
slide 33
99
What can we do if our epidural is only providing a unilateral block?
**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.
## Footnote
not on a slide just discussed in class
100
What does the subarachnoid space contain?
CSF, nerve roots, and the spinal cord itself
## Footnote
slide 34
101
What characteristic sensation is felt as the needle goes through the dura mater?
pop
## Footnote
slide 34
102
What is contained in the subdural space?
Nothing. Its a **potential space** between the dura and arachnoid mater.
## Footnote
slide 35
103
What happens if anesthetic is inadvertently injected into the subdural space with epidural dosing vs spinal dosing?
**epidural dosing**: "high spinal effect" (the medication effects a larger area than intended)
**spinal dosing**: failed spinal block
## Footnote
slide 35
104
Where do C1-C7 spinal nerves exit the spinal column?
above their corresponding vertebra
## Footnote
slide 37
105
Where does C8 spinal nerve exit the spinal column?
below C7
## Footnote
slide 37
106
Where do the thoracic, lumbar, sacral, and coccyx spinal nerves exit the spinal column?
below their corresponding vertebra
## Footnote
slide 37
107
How are spinal nerves formed?
By joining the anterior (ventral) and posterior (dorsal) nerve **roots** together.
## Footnote
slide 37
108
What information does the anterior (ventral) nerve root carry? From where to where?
carries motor and autonomic information from the spinal cord to the body
## Footnote
slide 37
109
What information does the posterior (dorsal) nerve root carry? From where to where?
sensory information from the body back to the spinal cord
## Footnote
slide 37
110
What is the definition of a dermatome?
an area of skin that recieves sensory nerves from a single spinal nerve root.
## Footnote
slide 38
111
What dermatome level(s) supplies the anterior and inner surface of the lower limbs?
L1-L4
## Footnote
slide 39
112
What dermatome level(s) supplies the foot?
L4, L5, S1
## Footnote
slide 39
113
What dermatome level(s) supplies the medial side of the great toe?
L4
## Footnote
slide 39
114
What dermatome level(s) supplies the posterior and outer surface of the lower limbs?
S1, S2, L5
## Footnote
slide 39
115
What dermatome level(s) supplies the lateral margin of foot and little toe?
S1
## Footnote
slide 39
116
What dermatome level(s) supplies the perineum?
S2, S3, S4
## Footnote
slide 39
117
What dermatome level(s) supplies the level of the umbilicus?
T10
## Footnote
slide 39
118
What dermatome level(s) supplies the inguinal or groin regions?
T12
## Footnote
slide 39
119
What dermatome level(s) supplies the clavicles?
C5
## Footnote
slide 39
120
What dermatome level(s) supplies the lateral parts of the upper limbs?
C5, C6, C7
## Footnote
slide 39
121
What dermatome level(s) supplies the medial sides of the upper limbs?
C8, T1
## Footnote
slide 39
122
What dermatome level(s) supplies the thumb?
C6
## Footnote
slide 39
123
What dermatome level(s) supplies the hand?
C6, C7, C8
## Footnote
slide 39
124
What dermatome level(s) supplies the ring and little fingers?
C8
## Footnote
slide 39
125
What dermatome level(s) supplies the level of the nipples?
T4
## Footnote
slide 39
126
What dermatome level(s) supplies the face?
Trick question. Face is supplied by cranial nerve 5 (V), not spinal nerves.
| CN V = Trigeminal
## Footnote
slide 40
127
What are the three branches of the trigeminal nerve?
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)
## Footnote
slide 40
128
What is the desired dermatome level to block for peri-anal/anal surgery?
| What is the other name for this type of block?
S2-S5
| "saddle block"
## Footnote
slide 41
129
What is the desired dermatome level to block for foot/ankle surgery?
L2
## Footnote
slide 41
130
What is the desired dermatome level to block for thigh/lower leg/knee surgery?
L1
## Footnote
slide 41
131
What is the desired dermatome level to block for vaginal delivery/uterine/hip procedure/tourniquet/TURP?
T10
## Footnote
slide 41
132
What is the desired dermatome level to block for scrotum procedure?
S3
## Footnote
slide 41
133
What is the desired dermatome level to block for penis procedure?
S2
## Footnote
slide 41
134
What is the desired dermatome level to block for testicular procedure?
T8
*testicles are embryonically derived from the same level as the kidneys for pain transmission (T10-L1)*
## Footnote
slide 41
135
What is the desired dermatome level to block for urologic/gynecologic/lower abdominal procedure?
T6
## Footnote
slide 41
136
What is the desired dermatome level to block for c-section/upper abdominal procedures?
T4
*sometimes may require concomitant general anesthesia due to vagal stimulation from abdominal traction*
## Footnote
slide 41
137
How does LA work when injected into the subarachnoid space?
LA acts on the myelinated preganglionic fibers of the spinal nerve roots. Inhibits neural transmission in the superficial layers of the spinal cord.
## Footnote
slide 43
138
How does LA work when injected into the epidural space?
Diffusion and leakage.
Diffusion through the dural cuff to reach nerve roots.
Leakage through the intervertebral foramen into the paravertebral area *(highlighted in green)*
## Footnote
slide 43
139
What is the MOST reliable factor affecting how far and wide the anesthetic speads when using hypo/isobaric solutions for **SAB**.
DOSE
## Footnote
slide 44
140
For what solutions is the relative density of the anesthetic to CSF crucial in determining how is spreads?
Hyperbaric solutions
## Footnote
slide 44
141
Low CSF volume correlates to ------------- spread of LA in the intrathecal space.
increased or extensive
## Footnote
slide 44
142
What factors decrease CSF volume which in turn requires less LA dose?
pregnancy, advanged age
143
How do nerves change with advanced age?
They are more vulnerable to LA.
## Footnote
slide 44
144
What are 4 controllable factors that affect the spread of LA for SAB?
1. Baracity
2. Patient Position
3. Dose
4. Site of injection
## Footnote
slide 44
145
What are 3 non-controllable factors that affect the spread of LA for SAB?
1. Volume of CSF
2. Increased intra-abdominal pressure (obesity, pregnancy)
3. Age (elderly)
## Footnote
slide 44
146
What 5 factors DO NOT affect the spread of LA for SAB?
1. Barbotage
2. Speed of injection
3. Orientation of bevel
4. Addition of vasoconstrictor
5. Gender
## Footnote
slide 44
147
What are 3 controllable factors that significantly affect spread of LA with **epidural** injection?
1. Local anesthetic volume **(most important *drug* related factor)**
2. Level of injection **(most important *procedure* related factor)**
3. Local anesthetic dose
## Footnote
slide 45
148
149
What are 2 controllabel factors that have a *small* effect on spead of LA when injected into the **epidural** space?
1. Local Anesthetic concentration
2. Patient position
## Footnote
slide 45
150
What is 1 non-controllable factor that has a *small* effect on spread of LA when injected into the **epidural** space?
Patient height
*Shorter stature may need less dose but this is controversial.*
## Footnote
slide 45
151
What 3 controllable factors *do not* affect spread of LA when injected into the **epidural** space?
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
## Footnote
slide 45
152
If injected into the lumbar region of the epidural space, which direction will the LA spread?
mostly cephalad
## Footnote
slide 45
153
If injected into the cervical region of the epidural space, which direction will the LA spread?
mostly caudad
## Footnote
slide 45
154
If injected in the mid-thoracic region of the epidural space, which direction will LA spread?
equidistant both cephalad and caudad
## Footnote
slide 45
155
What order are types of nerve fibers affected by LA?
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
## Footnote
slide 46
156
What function do A-alpha fibers have?
skeletal muscle movement and proprioception
## Footnote
slide 46
157
What function do A-beta fibers have?
touch and pressure
## Footnote
slide 46
158
What function do A-gamma fibers have?
skeletal muscle tone
## Footnote
slide 46
159
What function do A-delta fibers have?
fast pain, temperature, and touch
## Footnote
slide 46
160
What function dorsal root C fibers have?
slow pain, temperature, and touch
## Footnote
slide 46
161
How is the sympathetic nervous system affected by LA when ANS B and C fibers are blocked?
decreased sympathetic tone
so we have decreased BP and HR
## Footnote
slide 47
162
What is differential blockade?
refers to how different types of nerve fibers have varying sensitivities to local anesthetic which affects the level of block acheived
## Footnote
slide 47
163
When does sensory blockade occur?
| In reference to differential blockade?
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.*
## Footnote
slide 47
164
When does autonomic blockade occur?
| In reference to differental blockade?
At even lower LA concentrations than sensory requires which leads to the highest level of blockade.
## Footnote
slide 47
165
If sensory block occurs at T8, where will motor and autonomic block occur?
SNS block T2-T6
Motor block T10
## Footnote
slide 48
166
At what level is the cardioaccelerator nerve?
T1-T4
*Anytime the SNS block reaches this, we will see decreased HR and BP*
## Footnote
slide 48
167
In what order do the differential nerve fibers recovery from blockade?
Opposite order of block.
So motor blocks last and recovers first. SNS blocks first and recovers last.
## Footnote
slide 49
168
What is our preferred method of assessing sensory block?
temperature
*It is the first sense to be blocked. Second is pain, last is touch/pressure*
## Footnote
slide 50
169
What scale is used to monitor motor block?
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)
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What does the modified bromage scale specifically evaluate?
the function of lumbosacral nerves; does NOT assess movement above these regions
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How is preload affected by neuraxial anesthesia?
Decreased.
Sympathectomy causes veins to dilate leading to blood pooling in the periphery and reducing the blood returned to the heart.
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How is afterload affected by neuraxial anesthesia?
Decreased.
Sympathectomy partially dilates arterial circulation.
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How much (%) is SVR affected by neuraxial anesthesia in a healthy patient?
about 15%
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How much (%) is SVR affected by neuraxial anesthesia in an elderly or cardiac patient?
can decrease up to 25%
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How is cardiac output affected by neuraxial anesthesia?
May initially increase then gradually decrease due to decrease in SVR and venous return leading to a reduced stroke volume
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How is HR affected by neuraxial anesthesia?
Decreased due to blockade of cardiac accelerator fibers and activation of reflexes.
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What reflexes cause bradycardia due to neuraxial anesthesia?
Bezold-Jarisch Reflex and Reverse Bainbridge Reflex
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What is Bezold-Jarisch reflex?
Response to ventricular underfilling potentially leading to a significant bradycardia and asystole.
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What receptors mediate the Bezold-Jarisch reflex? What medication reverses this reflex?
Mediated by 5-HT3 receptros in the vagus nerve and ventricular myocardium.
Reversed by Zofran.
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What is the Reverse Bainbridge reflex?
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.
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How much does the reverse bainbridge reflex decrease HR?
by about 20 bpm
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What happens if there is unopposed parasympathetic tone to the cardioaccelerator fibers caused by sympathetic block?
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.*
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When does sudden cardiac arrest occur after neuraxial anesthesia?
20-60 minutes after onset of LA
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What are 4 interventions to prevent spinal anesthesia induced hypotension?
1. Vasopressors
2. 5-HT3 Antogonists
3. Fluid management
4. Positioning
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Which is better for preventing spinal anesthesia induced hypotension through fluid management: Co-loading or Pre-loading?
Co-loading
Administering IV fluids right after the spinal block rather than pre-block hydration to prevent drops in blood pressure
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What is the dose of fluid we give for co-loading hydration for adults?
15 ml/kg
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