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6901 > Neuraxial > Flashcards

Neuraxial Flashcards

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1
Q

5 different types of central neuraxial techniques

A 
Subarachnoid:
-Spinal
-Intrathecal
-Spinal Anesthetic Block (SAB)
Epidural
-Epidural
-Caudal
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2
Q

Spine vertebrae (different sections, how many per section)

A

Cervical: 7
Thoracic: 12
Lumbar: 5
Sacral: 5

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3
Q

Vertebrae components

A 
Vertebral body
Pedicles (2)
Transverse Processes (2)
Laminae (2)
Spinous process
Articular processes (4)
-Superior (2) vs Inferior (2)
-Stack to make the intervertebral foramina
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4
Q

Spinous processes at cervical/thoracic level vs lumbar

A 
Cervical/Thoracic:
-Angles in caudal direction, overlap
-Need to adjust needle angulation to access epidural space
Lumbar
-Easier to access
-Less acute angle, more open space
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5
Q

Spinal cord (adult) terminates at ____

A

L1-L2

  • Important for spinal technique, need to enter below this level so you don’t injure the cord
  • Epidural doesn’t necessarily follow this since you don’t (aren’t supposed to) enter this space
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6
Q

Ligaments supporting the spinal cord

A 
Supraspinous
-Joins the apexes of the spine of the vertebrae
-Major ligament in cervical and thoracic spine
Interspinous
-Joins spinous processes
-Very thin
Flavum
-3-5mm thick
-Helps maintain posture
-Yellow color
-Right before epidural space
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7
Q

Meninges (3 different layers and characteristics)

A 
3 membranes:
Dura
-Outermost layer, thick
-Most of the protection of the CNS
-Feels like popping through a water balloon
Arachnoid
-Thin
-Very close to the dura matter in the back (minimal subdural space)
-Subarachnoid space is under this
Pia
-Thin
-Directly covers the spinal cord
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8
Q

Epidural space

A
  • Runs entire length of the spine
  • Segmented and interconnected
  • Contains: Blood vessels, fat, lymphatics, nerve roots
  • Typical distance from skin->epidural space in adults = 5-8cm
  • Average lumbar AP distance = 5mm
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9
Q

Spinal blood supply

A 
Anterior spinal artery
-2/3 of anterior cord
-originates from vertebral artery
Posterior spinal arteries (2)
-1/2 of posterior cord
-originates from cerebellar arteries
Segmental spinal arteries
-artery of Adamkiewicz: anterior lower 2/3 of cord
Veins: Spinal veins (3 anterior, 3 posterior) communicate with epidural veins
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10
Q

Cerebral Spinal Fluid (characteristics, where it’s produced, how much is produced, specific gravity)

A 
Characteristics 
-Clear
-Occupies subarachnoid space
-Acts as a cushion and shock absorber
Produced in choroid plexus
-500mL/day
Specific gravity: 1.004-1.009
-Affect drug choice
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11
Q

Surgical types appropriate for neuraxial anesthesia

A

General surgery (below bellybutton)
Urology procedures
Rectal procedures
Lower extremity procedures

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12
Q

Pros of neuraxial anesthesia

A 
Narcotic sparing
Blunted stress response
Decreased blood loss (tourniquet use)
Can do cases awake (C-section, TURP)
-Safer for less optimized patients
Less overall med usage (less N/V, alert)
Avoid airway manipulation, meds associated with it
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13
Q

3 absolute contraindications for neuraxial anesthesia

A

Patient refusal/inability to cooperate
Localized sepsis (in area needle will enter)
Increased ICP

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14
Q

Relative contraindications for neuraxial anesthesia

A

Previous spine surgery
-Variable block d/t epidural space violation (rather than contraindicated because of complications)
-Ligaments aren’t there for landmarks
Evidence for other neurological issues aren’t rooted in evidence
-Back pain, spinal stenosis, MS
-Spina bifida: Increased risk of damage to neurological structures
Aortic stenosis
-D/t decreased afterload from vasodilation -> cardiac/circulatory arrest
Hypovolemia
Thromboprophylaxis
Coagulopathies
-Plt<100,000
-PT or aPTT 2x normal value
Infection
-OK if afebrile and being treated

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15
Q

Differential blockade

A

When transmission is altered in one type of nerve fiber but not another

  • Sympathetic=always the first to go/spreads out to the furthest dermatomes. 2 above sensory
  • Sensory=2 above motor
  • Motor
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16
Q

Myelination and Function of A-a, A-B, A-d, B, and C fibers

A

A-a: Heavy myelination, Motor
A-B: Moderate myelination, Touch/Pressure
A-d: Light myelination, Pain/Temperature
B: Light myelination, Preganglionic Autonomic
C: No myelination, Pain/Temperature

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17
Q

Mechanism of Action of blockade (Primary and secondary)

A

Bind to Na channel in inactive state, stop potentiation
Primary: Spinal roots
Secondary: Spinal cord, brain

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18
Q

Factors that affect the level of blockade

A 
Patient position
Baricity of drug
Drug dose/volume
Site of injection
Others
-Age
-Spinal issues
-Intra-abdominal pressure (pregnant, spinal column Is smaller/compressed -> less meds will spread more)
-Injection pressure
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19
Q

Baricity (CSF SG, ratios of hyper/hypo/iso)

A

How LA is compared to the CSF (ratio of LA SG: CSF SG)
-Resting position of 2 fluids with different specific gravities when they’re mixed
CSF SG: 1.004-1.009
Hyperbaric: SG>1.015
-Add dextrose
-Drug sinks to gravity
Isobaric: SG=1
-Add NS or CSF
-Use for hip cases so when they lay on their side both LEs stay numb
Hypobaric: SG<0.999
-Add sterile water (not really used in practice)

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20
Q

Factors you can control that contribute to the pharmacological spread

A

Total dose of drug
Site of injection
Baricity of drug
Patient position after injection

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21
Q

Cardiovascular effects of neuraxial block

A

Arterial dilation
Decreased SVR
Increased venous pooling
Decreased preload

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22
Q

Where sympathetic fibers arise from vs sympathetic cardio accelerator fibers

A

Sympathetic fibers: T5-L1 (vasomotor tone)
Sympathetic cardio accelerator fibers: T1-T4
-Unopposed vagal tone -> Bradycardia/Asystole

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23
Q

Treatment for cardiovascular effects after neuraxial block

A 
IVF to increased preload
-Colloid vs crystalloid is controversial
Alpha/Beta agonists
5-HT3 antagonists
Atropine if it's a high spinal
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24
Q

Pulmonary effects of neuraxial block

A 
Loss of accessory muscles
Loss of perception of breathing
Small decreased in VC
Phrenic nerve impairment if total spinal (C3-C5)
Impaired cough
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25
GI effects of neuraxial block
Unopposed vagal tone Increased peristalsis Relaxed sphincters
26
Miscellaneous effects of neuraxial block
Decreased thermoregulation | Decreased stress response
27
Immediate complications of neuraxial block
``` Total spinal -If epidural volume is injected into spinal space (20mL vs 3mL), avoid with test dose Cardiac arrest Failed spinal GI complications IV injection/LAST ```
28
Complications of total spinal block
Rapid onset, ascends into cervical levels | -Restless, hypotensive, bradycardic, apneic
29
Complications of IV injection/LAST
Restless, seizures, coma, cardiac collapse | -Follow LAST protocol
30
How to avoid IV injection during neuraxial block
Always aspirate on epidural catheter before injecting (blood if intravascular, although slow; CSF if past dura) Give test dose after placing an epidural catheter
31
How to do test dose on epidural catheter, what to watch for
- 3-5mL 1.5% lidocaine with 1:200,000 Epi - Rules out intrathecal placement: Would get numbness in toes within 10 seconds if it was spinal - Rules out intravascular placement: Would see 15% increase in baseline HR because of Epi
32
4 potential places epidural catheters could be
Epidural space Epidural space: In blood vessel Intrathecal/Subarachnoid space (wet tap) Flavum (can't thread catheter)
33
Overall complications to tell patients before neuraxial block
``` Post dural puncture headache (PDPH) Urinary retention Backache Transient neurological symptoms (TNS) Caudal equina syndrome Nerve injury ```
34
Post dural puncture headache (PDPH) factors, mechanism, symptoms, treatment
Factors -Needle guage (spinal needles=smaller, 24-29g, less likely 1/100 vs epidural needles 17-18g, more likely 60-80%) -Cutting (more likely) vs pencil tip -Bevel direction (parallel to dural fibers minimize risk) Mechanism -Decrease in CSF -> brain/brainstem drops into the foramen magnum -> tug on meninges -Possibly vasodilatory mechanisms from lack of CSF Symptoms -Light sensitivity -Postural headache (have to lay flat, less pressure on brainstem dropping) -Nausea/Vomiting Treatment -Gold standard: Blood patch -Sphenopalatine ganglion block -Fluid, caffeine, rest
35
Neurological injury from neuraxial blocks
Rare, subdural or epidural hematoma -Can usually rule out patients who this could happen to during preop interview (bruising/bleeding questions, thrombophylaxis, thrombocytopenia) Causes -Needle trauma, surgical trauma, positional -Chemical (drug), virus, bacteria -Ischemia *Devastating effect, can lead to paralysis *Neuro checks, referral for rapid decompression if needed (goal=<8 hours after symptoms present)
36
Cauda equina syndrome (Symptoms, cause)
Persistent paralysis of nerves of cauda equina -> LE weakness, bowel/bladder dysfunction Associated with microcatheters, small needles, repeat dosing, hyperbaric local anesthetics (5% lidocaine) -Repeat spinal dosing=risky -FDA removed small needles and microcatheters in 1992
37
Transient neurological syndrome
``` Symptoms -Pain in buttocks/LEs -Bowel/bladder dysfunction Risk -5% Lidocaine (Other anesthetics have been implicated but it'll much more prevalent after spinal lidocaine) -Chloroprocaine (when it used to have preservatives) Treatment -Usually resolves on its own -Can give NSAIDs ```
38
Infection after neuraxial block (2 types, treatment, prevention)
``` Meningitis -Contaminated equipment -Glass particles -Coring of tissue Epidural abscess -Back pain with fever Treatment -Antibiotics, surgical decompression Prevention -Sterile field, remove catheters after 96 hours ```
39
Spinal needles
``` All have stylets to avoid coring Quinke -Standard cutting -22-25g Spotte, pencan, Whitacre -Non cutting, pencil tip -Different side port shapes -22-29g (smaller 24-29 need introducer needle ```
40
Difference between cutting and pencil tip needles
If name has "K" sound in it it's most likely a cutting needle - Cutting needles can pierce a cauda equina root without knowing (damage nerve) - Cutting needles give less perceptive feedback - PDPH is 3x higher when using a cutting needle vs pencil tip - Cutting needles can deviate
41
Epidural needles, catheters
``` Needles -Have a curve on the end to thread catheter -17-19g -Touhy, Crawford, Weiss Catheters -Single or multiple orifices -Wire reinforced -Usually 2g smaller than needle ```
42
How far to advance epidural catheter
3-5cm past how many cm it took to get to epidural space/loss of resistance
43
Sitting vs side lying positioning
Sitting - Easier to achieve interspinous space - Easier to assess midline - Easier to assess landmarks - Patients need to "round out" their back
44
Tuffier's Line
Top of iliac crests, intersects with spine at ~L4
45
Bromage grip
How to anchor needle when placing spinal - Nondominant hand grasps needle hub between pointer and thumb - Back of hand/fingers brace against patients back to stabilize your access point
46
What type of LA/what needle to use before spinal/epidural technique
10-20% lidocaine | 25g needle
47
Paramedian approach
~1'' off midline ~15 degree approach - Avoid in horizontal anatomy - Use if you can't get good space between vertebrae with rounding back out
48
Drugs for spinal (LA, opioids, adjunts)
``` LA -Bupivacaine -Tetracaine -Chloroprocaine Opioids -Morphine -Fentanyl -Dilaudid Adjunts -Vasoconstrictors -Alpha-2 agonists *Everything needs to be preservative free ```
49
Bupivacaine for spinal
0. 75% in dextrose (1.6-2mL) - Hyperbaric - Gives dense block up to T4 - Good for longer procedures (3 hours) 0. 5% (2.5-3mL) - Isobaric - Good for lateral procedures (hip) since won't sink - Same DOA and block density as .75%
50
Chloroprocaine for spinal
2-3% 2-2.5mL Lasts 1-1.5 hours -Good for outpatient surgery
51
Opioids for spinal
``` *Preservative free Morphine ->200mcg=little analgesic benefit with increased SE -Pruritis, N/V Dilaudid -70-100mcg -Less pruritic/N/V Fentanyl -25mcg ```
52
Vasoconstrictors in spinal
Epi - 1:1000, 0.1-0.2mL (~100mcg) - Do "Epi wash"=Aspirate 1mL into syringe and then squirt it out, use same syringe to draw up LA
53
Alpha 2 agonist in spinal
Precedex can prolong the duration of the block
54
Epidural volume, how to determine density and level
2mL/level Density=concentration Level=volume -Max spread occurs after 15-25 minutes
55
Bupivacaine in epidural
0. 5% for surgical anesthesia (careful, can get close to toxic doses/2.5-3mg/kg) 0. 25% for analgesia (not anesthetic dose) 0. 125% for sensory>motor block (postop pain relief)
56
Opioids in epidurals
``` Fentanyl 50-100mcg bolus Morphine 3mg (>3=high risk of respiratory depression) ```
57
OB epidural
0. 2% Ropivacaine with 2mcg/mL fentanyl - 8-10mL/hr - 4mL bolus q30min (PCA)
58
Ropivacaine in epidurals
0. 2% | - Analgesic block
59
Spinal vs epidural onset, duration, density
``` Onset -Spinal=quick -Epidural=variable Duration -Spinal=set -Epidural=variable Density -Spinal=set -Epidural=variable *Epidurals are customizable vs spinals-once injected they're done ```
60
Combined spinal epidural (advantages, disadvantages, approaches)
``` Advantages -Quick onset -Prolonged duration -Confirms needle is in epidural space Disadvantage -Can mask a patchy epidural for ~2hours Approaches -2 level (epidural normal, spinal 1 level down) -Needle through needle -Specialized combined CSE needles ```
61
Caudal anesthesia
Used in peds d/t ease of access Position: Prone, lateral -Palpate cornua of sacral hiatus -Needle advanced at steep angle between cornua -Popping sensation when entering sacral ventral canal -Needle angle lowered to parallel sacrum/spinal canal, advanced 1-3cm -Medication injected or catheter placed by catheter over needle technique 0.5-1mL will achieve umbilicus level coverage
62
How is the sympathetic blockade level judged
Temperature sensitivity
63
Neuraxial anesthesia doesn't block ____ nerve
X: Vagus -> unopposed parasympathetic tone
64
For spinal anesthesia what order are spinal nerves anesthetized in
1: Pre-ganglionic sympathetic 2: Temperature 3: Pinprick 4: Touch 5: Motor
65
Dermatome level for thoracic/upper abdominal/mid abdominal/lower abdominal/lower extremity epidural placement
``` Thoracic: T4-8 Upper abdominal: T6-8 Middle abdominal: T7-10 Lower abdominal: T8-11 Lower extremity: L1-L4 ```

6901 (9 decks)

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