Spinal/Epidural - Exam 1 Flashcards
(134 cards)
1
Q
What are the clinical indications for neuraxial anesthesia?
A
- Surgical procedures involving the lower abdomen, perineum, and lower extremities
- Orthopaedic surgery
- Vascular surgery on the legs
- Thoracic surgery (adjunct to GETA)
2
Q
What are the general benefits to neuraxial anesthesia?
A
Reduced:
- narcotics
- post op ileus
- thromboembolic events
- bleeding
- PONV
- resp. complications
3
Q
What are the “other benefits” to neuraxial anesthesia?
A
- Great mental alertness
- Less urinary retention
- Quicker to eat, void, and ambulate
- Avoid unexpected overnight admission from complications of general anesthesia
- Quicker PACU discharge times*
- Preemptive anesthesia
- Blunts stress response from surgery
4
Q
What are the relative contraindications to neuraxial anesthesia?
A
- spinal column deformities (spinal stenosis, kyphoscoliosis)
- preexisting disease of the spinal cord (MS, post polio)
- chronic headache/backache
- inability to preform SAB/epidural after 3 attempts
5
Q
What are the absolute contraindications for neuraxial anesthesia?
A
- Coagulopathy (Risk of epidural hematoma)
⚬ INR > 1.5 (ASRA)
⚬ Platelets < 100,000; consider trends*
⚬ Nagelhout x 2 (PT, aPTT, bleeding time)
⚬ Known coagulation disorder or taking anticoagulants - Patient refusal
- Evidence of dermal site infection
- Severe or critical valvular heart disease
⚬ AS =/< 1.0 cm2 or MS < 1.0 cm2 - HSS (Idiopathic hypertrophic subaortic stenosis)
- Operation > Duration of local anesthetic?
- Increased ICP
- Severe CHF
⚬ EF < 30-40%?
⚬ Preload dependence
6
Q
Describe onset of spinal vs epidural
A
Spinal: rapid (5 min)
Epidural: slow (10-15 min)
7
Q
Describe spread of spinal vs epidural
A
Spinal: higher than expected, may extend extracranially
Epidural: as expected, can be controlled with volume of LA
8
Q
Describe the nature of block of spinal vs epidural
A
Spinal: dense
Epidural: segmental
9
Q
Describe motor block of spinal vs epidural
A
Spinal: dense
Epidural: minimal
10
Q
Describe hypotensive effects of spinal vs epidural
A
Spinal: likely
Epidural: less than spinal
11
Q
Describe duration of spinal vs epidural
A
Spinal: limited and fixed
Epidural: unlimited
12
Q
Describe placement level of spinal vs epidural
A
Spinal: L3-4, L4-5, L5-S1
Epidural: any level
13
Q
Describe difficulty of placement of spinal vs epidural
A
Spinal: none
Epidural: more skilled required
14
Q
Describe dosing of local anesthetic for spinal vs epidural
A
Spinal: dose-based (mg)
Epidural: volume based
15
Q
Describe concentration of LA with spinal vs epidural
A
Spinal: concentrated and fixed (5 min)
Epidural: varies
16
Q
Describe local anesthetic toxicity with spinal vs epidural
A
Spinal: no
Epidural: yes
17
Q
Describe gravity influence of spinal vs epidural
A
Spinal: yes, baricity
Epidural: yes, position
18
Q
Describe manipulation of dermatome spread after dosing in spinal vs epidural
A
Spinal: yes (1st 5 min): position changes, baricity, dose
Epidural: incremental dermatome spread based on volume 1-2 ml per segment
19
Q
How many vertebrae do we have? How many of each segments?
A
33 total
C: 7
T: 12
L:5
S:5
Coccyx: 4
20
Q
What are the abnormal curvatures of the spine?
A
21
Q
Each vertebra, except for ___, is divided into 2 main parts.
The anterior segment is known as what?
The posterior segment of known as what?
A
C1
Body
Vertebral arch
22
Q
What 2 structures link the anterior and posterior segments of the vertebra?
A
Lamina
Pedicle
23
Q
What does the vertebral foramen house?
A
spinal cord, nerve roots, and the epidural space, which is a protective cushioning
area around the spinal cord.
24
Q
On a vertebrae, the ______ ______ stick out to the sides (lateral), while the _____ _____ stick out towards the back (posterior).
A
transverse processes
spinous processes
25
What attaches to the transverse processes and spinous processes? Why?
What is something specific the spinous process is used for?
Muscles!
They help stabilize and support the spine
The spinous process is also used as a landmark to find the middle line of the back
26
What are the spinous process differences in the vertebrae?
* The lumbar vertebrae are different from the thoracic and cervical vertebrae because of the orientation of the spinous processes.
* Cervical and thoracic spinous processes tilt downward (caudal direction), requiring a needle approach from above (cephalad approach).
* Lumbar spinous processes stick out directly backwards (posterior), which makes it easier to reach the spaces around the spinal cord, such as the epidural and intrathecal spaces
27
What are intervertebral disc?
Soft pads between each vertebra that act as shock absorbers
28
What are intervertebral foramina?
Openings between each vertebrae where spinal nerves exit the spine
29
In regards to formation of foramina:
The anterior side of the foramen is formed by what 2 things?
The posterior side of each foramen is formed by the _____ _____, which are part of the vertebrae
vertebral body & intervertebral disc
facet joints
30
When intervertebral discs wear down, what becomes smaller?
What does this cause?
Foramina
This narrowing can press on the spinal nerves, causing pain, numbness, weakness
31
Each facet joint is made by what 2 parts?
The inferior articular process of one vertebra connects with the superior articular process of the vertebra right below it
32
What is the function of the facet joints?
What happens if one gets injured?
- help guide and limit spine movement, keeping the back's motion controlled
injury impact: if a facet gets injured, it can press on nerves
- symptoms: pain and muscle spasms
33
What landmark is the superior aspect of iliac crest?
L4
34
What landmark is the posterior superior iliac spine?
S2
35
What is intercristal line?
Tuffier's Line
- horizontal line that runs across the top edges of iliac crests and matches L4 vertebra
- the space above aligns with L3-L4 vertebrae
- space below aligns with L4-L5 vertebrae
36
What does the intercristal line corresponds to in infants up to a year?
L5-S1 intervertebral space
37
The lamina of ___ is incomplete and bridges only by ligaments
S5
38
What is the sacral hiatus?
Located at base of the sacrum and aligns of S5 vertebra
- acts as an access point to caudal anesthesia
39
What is the sacral cornea?
Projections of the articular processes are known as cornu
- the sacral cornu are the horns that guard the area of the sacral hiatus
- landmark for caudal anesthesia
40
The spinal cord as a ____ origin, which is the:
Rostral
Medulla oblongata
41
Explain conus medullaris
Where does this end in adults and infants?
This is where the spinal cord tapers off at the end
Adults: L1 and L2
Infants: L3
42
Explain caudal equina
What nerves are included here?
A bundle of spinal nerves extending from conus medullar is to dural sac
- consists of nerve roots form L2-L5 and coccygeal nerve
43
What ends at the dural sac?
Where does this end in adults and infants?
Subarachnoid space
Adults: S2
Infants: S3
44
What is the filum terminale?
Where does it extend from/to?
A continuation of Pia mater that continues downward from the end of the spinal cord
Extends from conus medullaris to the coccyx
45
What is the main function of the filum terminale?
Anchor the spinal cord to the coccyx
46
What are the parts of the filum terminale?
￭ Internal Filum Terminale:
- Begins at the conus medullaris, extending to
the dural sac.
￭ External Filum Terminale:
- Starts from the dural sac and extends into the sacrum
47
What is the blood supply for the spinal cord?
One anterior spinal artery
Two posterior spinal arteries
48
Where does the anterior spinal artery originate from?
What does this supply in the spinal cord?
Vertebral artery
- Motor portion of the spinal cord; anterior 2/3
49
Where do the 2 posterior spinal arteries emerge from? Originate from?
What does this supply in the spinal cord?
Emerges from cranial vault, originates from the vertebral artery
Supplies sensory portion
50
How does the spinal cord protect itself from ischemia?
The posterior spinal arteries are paired and have many connections (collateral anastomotic links) from the subclavian and intercostal arteries.
- These connections help protect the sensory
part of the spinal cord from ischemia.
## Footnote
The anterior spinal artery, being a single artery, does not have as many protective links, making the motor part more vulnerable to ischemia
51
What is anterior spinal artery syndrome?
Ischemia affecting anterior spinal artery
- can lead to motor paralysis, loss of pain/temp sensation
52
What are causes of ischemia associated with anterior spinal artery syndrome?
⚬ Low blood pressure (profound hypotension).
⚬ Mechanical blockage.
⚬ Blood vessel disease (vasculopathy).
⚬ Bleeding (hemorrhage).
53
What is the artery of adamkiewicz?
Where does this arise from?
A connection that supplies blood to the lower 2/3 of the spinal cord
- From the aorta between the T7 and L2 regions
## Footnote
Damage to this artery can also lead to anterior spinal artery syndrome
54
Where is the supraspinous ligament?
Runs along the back, connecting the tips of the spinous processes from the upper back down to the lower back (in yellow)
55
Where is the interspinous ligament?
Located between the spinous processes, providing stability by joining adjacent vertebrae. (in green)
56
Where is the ligamentum flavum?
What does piercing this ligament indicate?
They are particularly thick in the lower back and form the sidewalls of the
space outside the spinal cord (epidural space). (in blue)
Entry into epidural space
57
Where is the posterior longitudinal ligament?
Runs along the back side of the vertebral bodies inside the spinal column. (in purple)
58
Where is the anterior longitudinal ligament?
What else does this connect to?
Attached to the front of the vertebral bodies, running the length of the spinal column (in red)
Connects to the outer fibers of the intervertebral discs, helping to bind vertebrae together
59
List the layers that are traversed using a midline approach from outer to inner
Skin
Subcutaneous fat
Supraspinous ligament
Interspinous ligament
Ligamentum Flavum
Dura Mater
Subdural space
Arachnoid mater
Subarachnoid space
## Footnote
Some say school is like doing squats and sharting
60
List the layers that are traversed using a paramedian approach from outer to inner
Skin
Subcutaneous fat
Ligamentum flavum
Dura mater
Subdural space
Arachnoid mater
Subarachnoid space
61
Why would you use a paramedian approach for spinal?
What does positioning look like for this?
When interspinous ligament is calcified or pt cannot flex spine (scoliosis)
Can be performed while pt is sitting, lying on side, or face down
62
What is the order of meningeal layers from outer to inner?
Dura mater
Arachnoid mater
Pia mater
63
What does the epidural space contain?
Fat, nerves, lymphatics, and small blood vessels (epidural veins)
64
What is the subdural space considered?
A potential space
65
What does the subarachnoid space contain?
CSF: cushions and protects spinal cord
Nerve roots
spinal cord
66
Describe drug absorption in the epidural space
Fatty tissue in this area can absorb and decrease the availability of certain drugs
## Footnote
Ex: bupivacaine is aborbed more than lidocaine, fentanyl, or morphine
67
What is another name for the epidural veins?
Explain their significance
Batson's Plexus
- valveless and form a plexus draining blood from the cord and it's linings
- density of veins increases laterally
- engorged under conditions like obesity and pregnancy, increasing risk during needle procedure
68
What is the plica mediana dorsalis?
What is the significance?
Connective tissue that divides R/L epidural space
- located between ligamentum flavum and dura mater
Controversial if exists, but if so, may act as a barrier within epidural space and affect how meds spread (unilateral block)
69
Where is the primary target for spinal?
Subarachnoid space
70
What is the characteristic sensation during spinal anesthesia to help direct placement?
a characteristic "pop" is often felt
when the needle passes through the outer membrane, the dura mater
71
What is significant in regards to epidural dosing?
If local anesthetic is inadvertently injected
here during an epidural, it could cause a "high spinal" effect, meaning the medication affects a larger area than intended.
72
An accidental injection into the subdural space during spinal anesthesia can result in:
A failed spinal block
73
What is the dura mater?
Where is this located?
Starts at the large opening at the foramen magnum and extends down to the dural sac.
A tough fibrous shield that protects the spinal cord
74
What is the arachnoid mater?
Where is this located?
A thin layer of connective tissue that acts as a protective middle layer that lies directly beneath the dura mater.
75
What is the Pia mater?
Where is this located?
A highly vascular structure and delicate innermost layer that directly covers the spinal cord
## Footnote
Should never be punctured during spinal as it is directly attached to the surface of the spinal cord
76
How many spinal nerves are there?
Describe each section of the vertebra amount
31 pairs
C: 8
T: 12
L: 5
S: 5
Coccyx: 1
77
What is the general rule for location of spinal nerves?
What is the exception?
Each nerve exits the spine above it's corresponding vertebra (C1 nerve exits above C1 vertebra)
C8 is the exception. This nerve exits below the C7 vertebra
78
Explain the 2 parts of the nerve root
Anterior (Ventral) Nerve Root: Carries motor (movement) and autonomic (automatic body processes) information from the spinal cord to the body.
Posterior (Dorsal) Nerve Root: Brings sensory information from the body back to the spinal cord.
79
What is a dermatome?
An area of skin that receives sensory nerves from a single spinal root
80
What is the target for a spinal?
LA acts on myelinated pre-ganglionic fibers of spinal nerve roots
- also inhibits neural transmission in the superficial layer of spinal cord
81
Explain diffusion and leakage in regards to an epidural
Diffusion: LA diffuse through dural cuff to reach nerve roots
Leakage: LA can leak through intervertebral formant into paravertebral area (highlighted in green)
82
What does the spread of local anesthetic in spinal or epidural space determine?
Block height
83
What are factors that affect the spread of local anesthetic distribution with spinal?
Controllable vs non-controllable
Controllable Factors:
* Baricity
* Patient Position
* Dose
* Site of Injection
Non-Controllable Factors:
* Volume of CSF
* Increased Intra-abdominal
Pressure (obesity,pregnancy)
* Age (elderly)
84
What are factors that do not affect the spread of local anesthetic distribution with spinal?
* Barbotage (repeated aspiration and reinjection of CSF)
* Speed of Injection
* Orientation of Bevel
* Addition of Vasoconstrictor
* Gender
85
What is the most reliable factor affecting how far and wide the anesthetic spreads with a spinal?
Dose
86
Low CSF volume correlated to what?
What else is this associated with?
Extensive spread of LA in intrathecal space
Advanced age: neural nerves are vulnerable to LA and CSF volume decreases
Pregnancy: decreased CSF due to increased abd. pressure
87
What are factors that significantly affect LA spread in epidural?
Controllable Factors
* Local Anesthetic Volume (Most important drug related factor)
* Level of injection (Most important procedure related)
factor
* Local Anesthetic dose
Non-Controllable Factors
Pregnancy
Old Age
88
What are factors that have a small effect on spread with epidural?
Controllable Factors
* Local Anesthetic Concentration
* Patient Position
Non-Controllable Factors
* Height (Taller or shorter stature may
slightly affect spread)
89
What factors do not affect the spread of LA in epidural?
Controllable Factors
* Additives in the Anesthetic (Might change
onset time or duration but not spread.)
* Direction of the Bevel of the Needle
* Speed of Injection
90
Explain injection levels and spread dynamics during epidural
* Lumbar Region: mostly spreads cephalad.
* Mid-Thoracic Region: Spread is balanced both cephalad and caudad.
* Cervical Region: spreads caudad
91
Nerve fiber chart
92
Explain differential blockage
Refers to how different types of nerve fibers have varying sensitivities to LA, affecting the level of block achieved
* 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.
* Autonomic Blockade: Requires even lower concentrations of LA, affecting neither sensory nor motor neurons, leading to the highest level of blockade.
93
Explain the order in which nerves are affected during block and *briefly* what each does
B fibers: autonomic pre-ganglionic fibers (venodilation-hypotension)
C: pain/temp
A-delta: pain/temp
A-gamma: motor tone
A-beta: touch/pressure
A-alpha: motor and proprioception
94
What are the differential blockade zones?
Sensory: 2 levels higher than motor
SNS: 2-6 levels higher than sensory
## Footnote
This is a little confusing how it's worded this year, but from last year:
Sensory is site of injection, SNS is 2-6 above, motor is 2 below
95
What nerve fiber is blocked the longest?
B fibers
96
What is monitored during sensory block?
* Temperature: The first sense to be blocked; for example, the patient may not feel cold from an alcohol pad.
* Pain: The second sense to be blocked, assessed using stimuli like a pinprick.
* Touch or Pressure: The last sense to be blocked, involving light touch or pressure sensation.
97
What is monitored during motor block?
The modified Bromage scale
Scale Levels:
⚬ 0: No motor block.
⚬ 1: Slight motor block. The patient cannot raise an extended leg but can still move the knees and feet.
⚬ 2: Moderate motor block. The patient cannot raise an extended leg or move the knee but can move the feet.
⚬ 3: Complete motor block. The patient cannot move the legs, knees, or feet
98
What are the systemic effects of neuraxial anesthesia on preload and afterload?
Preload:
⚬ Decreases: Sympathectomy causes veins to dilate, leading to blood pooling in the periphery and reducing the blood returning to the heart.
Afterload:
⚬ Decreases: Sympathectomy partially dilates arterial circulation.
⚬ Effects in Healthy vs. Diseased Patients:
￭ Healthy Patients: Decrease in SVR by ~15%.
￭ Elderly or Cardiac Patients: SVR can decrease up to ~25%.
99
What are the systemic effects of neuraxial anesthesia on cardiac output?
⚬ Decrease in Venous Return and SVR: Leads to reduced stroke volume and CO.
⚬ Initial Response: CO may initially increase, then decrease over time due to changes in blood vessel dilation speeds.
100
What are the systemic effects of neuraxial anesthesia on HR?
⚬ Decrease Due to:
￭ Blockade of Cardiac Accelerator Fibers:
Reduces SNS tone, leading to decreased
heart rate.
￭ Activation of Reflexes:
- Bezold-Jarisch Reflex
- Reverse Bainbridge
## Footnote
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
Reverse Bainbridge Reflex: Triggered by
reduced stretching of heart's right atrium.
101
Why does sudden cardiac arrest happen in neuraxial anesthesia?
When does this usually occur?
Unopposed parasympathetic tone to the
cardioaccelerator fibers can result in profound bradycardia, hypotension, and sudden cardiac arrest.
- Can be seen young adults with high parasympathetic tone
20-60 min after onset of spinal
102
What are preventative measures for spinal-anesthesia induced hypotension?
Vasopressors
5-HT3 antagonists
Fluid management
Positioning
Anticholingerics
*See pg 53-54 for details
103
Explain the different types of fluid management for prevention of spinal-anesthesia induced hypotension
Co-loading: Administering intravenous fluids (around 15 mL/kg) right after the spinal block to prevent drops in
blood pressure.
Avoid Pre-loading: Pre-block hydration is not routinely recommended due to minimal impact on preventing hypotension.
104
Systemic effects of neuraxial anesthesia on pulmonary system
Usually minimal impact
- with high T4 dermatome spread, may see VT, RR, IRV, ERV decrease
- use caution with COPD
- feelings of dyspnea is normal
- apnea is rare, typically due to reduced blood flow to brainstem
*See pg 55 for more details
105
Parasympathetic innervation of GI is primarily via _____ nerve and originates where?
Vagus nerve
Medulla
106
Explain the difference in afferent and efferent parasympathetic effects on GI
⚬ Parasympathetic AFFERENT: transmits
sensations of satiety, distension, and
nausea
⚬ Parasympathetic EFFERENT: tonic
contractions, sphincter relaxation,
peristalsis, and secretion.
107
Sympathetic innervation of Gi tract terms from where?
T5-L2
108
Explain the afferent and efferent sympathetic effects on GI
⚬ Sympathetic AFFERENT: transmit
visceral pain
⚬ Sympathetic EFFERENT: inhibit
peristalsis and gastric secretion and
cause sphincter contraction and
vasoconstriction
109
What are the impacts of neuraxial anesthesia on GI?
Reduces sympathetic tone
Increases parasympathetic activity
Resulting changes in unopposed vagal tone
⚬ Relaxes Sphincters
⚬ Increases Peristalsis
⚬ Small, contracted gut with active peristalsis (20% incidence of N/V)
⚬ Increased GI blood flow
⚬ Nausea and vomiting (20% of the patients)
⚬ Reduces postoperative incidence of ileus in abdominal surgery
110
Systemic effects of neuraxial anesthesia on GU
No change in RBF when MAP is maintained
- sympathetic blockade above T10 affects bladder control (urianry sphincter tone relaxed)
With addition of neuraxial opiods:
- decrease detrusor contraction
- increase in bladder capacitance
- leads to urinary retention/incontinence
111
Systemic effects of neuraxial anesthesia on metabolic/endocrine
- activation of somatic and visceral afferent fibers from pain, tissue trauma, and inflammation caused elevated cortisol, epi, norepinephrine, vasopressin
- partially suppress or totally block neuroendocrine response
112
Which type of LA has more allergies?
Esters d/t PABA
113
What is the perservative in amides?
Methylparaben
114
T/F
There is cross sensitivity between esters and amides
False
115
Where are amides metabolized?
What about esters? What is the exception?
Amides: Liver
Esters: plasma (exception is cocaine)
116
Onset of action is dependent on:
pKa
117
Potency is dependent on:
Lipid solubility
118
Duration of action is dependent on:
Protein binding
119
T/F
LA work outside the cell
False!!
Inside the cell
120
Factors influencing vascular uptake and plasma concentration of LA
Site of injection
Tissue blood flow
Physiochemical properties
Metabolism
Addition of vasoconstrictor
121
Describe the differences in uptake of LA based on regional anesthetic technique
122
What is baricity?
Refers to the density of a local anesthetic solution compared to CSF
123
Define isobaric
Density = CSF
- has a baricity of 1, it's density matches CSF
- tends to stay where it's injected
124
Define hyperbaric
Density > CSF
- baricity >1
- sinks within CSF, moving downward from point of injection
125
Define hypobaric
Density < CSF
- baricity <1
- rises within CSF< moving upward from point of injection
126
Hyperbaric, isobaric, hypobaric drug chart
127
What are the high points (apex) when the pt is supine for SAB?
C3 and L3
128
What are the low points (trough) when the pt is supine for SAB?
T6 and S2
129
Spinal cord uptake of LA occurs due to ____ ____ nature of the drug
Lipid soluble
130
Spread of LA occurs in a ____ and _____ direction from the site of injection simultaneously
Cephalad
Caudad
131
T/F
There is no metabolism occurring in the CSF
Treu
132
T/F
All LAs are eliminated by reuptake
How?
True!
Vascular reabsorption via vessels in pia mater
133
What is the difference in spinal or epidural dosing?
You can do a lot of epidural re-dosing!
134
