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6901 > Neuraxial > Flashcards

Neuraxial Flashcards

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
Q

GI effects of neuraxial block

A

Unopposed vagal tone
Increased peristalsis
Relaxed sphincters

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26
Q

Miscellaneous effects of neuraxial block

A

Decreased thermoregulation

Decreased stress response

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27
Q

Immediate complications of neuraxial block

A 
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
Q

Complications of total spinal block

A

Rapid onset, ascends into cervical levels

-Restless, hypotensive, bradycardic, apneic

29
Q

Complications of IV injection/LAST

A

Restless, seizures, coma, cardiac collapse

-Follow LAST protocol

30
Q

How to avoid IV injection during neuraxial block

A

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
Q

How to do test dose on epidural catheter, what to watch for

A
  • 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
Q

4 potential places epidural catheters could be

A

Epidural space
Epidural space: In blood vessel
Intrathecal/Subarachnoid space (wet tap)
Flavum (can’t thread catheter)

33
Q

Overall complications to tell patients before neuraxial block

A 
Post dural puncture headache (PDPH)
Urinary retention
Backache
Transient neurological symptoms (TNS)
Caudal equina syndrome
Nerve injury
34
Q

Post dural puncture headache (PDPH) factors, mechanism, symptoms, treatment

A

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
Q

Neurological injury from neuraxial blocks

A

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
Q

Cauda equina syndrome (Symptoms, cause)

A

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
Q

Transient neurological syndrome

A 
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
Q

Infection after neuraxial block (2 types, treatment, prevention)

A 
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
Q

Spinal needles

A 
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
Q

Difference between cutting and pencil tip needles

A

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
Q

Epidural needles, catheters

A 
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
Q

How far to advance epidural catheter

A

3-5cm past how many cm it took to get to epidural space/loss of resistance

43
Q

Sitting vs side lying positioning

A

Sitting

  • Easier to achieve interspinous space
  • Easier to assess midline
  • Easier to assess landmarks
  • Patients need to “round out” their back
44
Q

Tuffier’s Line

A

Top of iliac crests, intersects with spine at ~L4

45
Q

Bromage grip

A

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
Q

What type of LA/what needle to use before spinal/epidural technique

A

10-20% lidocaine

25g needle

47
Q

Paramedian approach

A

~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
Q

Drugs for spinal (LA, opioids, adjunts)

A 
LA
-Bupivacaine
-Tetracaine
-Chloroprocaine
Opioids
-Morphine
-Fentanyl
-Dilaudid
Adjunts
-Vasoconstrictors
-Alpha-2 agonists
*Everything needs to be preservative free
49
Q

Bupivacaine for spinal

A
  1. 75% in dextrose (1.6-2mL)
    - Hyperbaric
    - Gives dense block up to T4
    - Good for longer procedures (3 hours)
  2. 5% (2.5-3mL)
    - Isobaric
    - Good for lateral procedures (hip) since won’t sink
    - Same DOA and block density as .75%
50
Q

Chloroprocaine for spinal

A

2-3% 2-2.5mL
Lasts 1-1.5 hours
-Good for outpatient surgery

51
Q

Opioids for spinal

A 
*Preservative free
Morphine
->200mcg=little analgesic benefit with increased SE
-Pruritis, N/V
Dilaudid
-70-100mcg
-Less pruritic/N/V
Fentanyl
-25mcg
52
Q

Vasoconstrictors in spinal

A

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
Q

Alpha 2 agonist in spinal

A

Precedex can prolong the duration of the block

54
Q

Epidural volume, how to determine density and level

A

2mL/level
Density=concentration
Level=volume
-Max spread occurs after 15-25 minutes

55
Q

Bupivacaine in epidural

A
  1. 5% for surgical anesthesia (careful, can get close to toxic doses/2.5-3mg/kg)
  2. 25% for analgesia (not anesthetic dose)
  3. 125% for sensory>motor block (postop pain relief)
56
Q

Opioids in epidurals

A 
Fentanyl 50-100mcg bolus
Morphine 3mg (>3=high risk of respiratory depression)
57
Q

OB epidural

A
  1. 2% Ropivacaine with 2mcg/mL fentanyl
    - 8-10mL/hr
    - 4mL bolus q30min (PCA)
58
Q

Ropivacaine in epidurals

A
  1. 2%

- Analgesic block

59
Q

Spinal vs epidural onset, duration, density

A 
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
Q

Combined spinal epidural (advantages, disadvantages, approaches)

A 
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
Q

Caudal anesthesia

A

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
Q

How is the sympathetic blockade level judged

A

Temperature sensitivity

63
Q

Neuraxial anesthesia doesn’t block ____ nerve

A

X: Vagus -> unopposed parasympathetic tone

64
Q

For spinal anesthesia what order are spinal nerves anesthetized in

A

1: Pre-ganglionic sympathetic
2: Temperature
3: Pinprick
4: Touch
5: Motor

65
Q

Dermatome level for thoracic/upper abdominal/mid abdominal/lower abdominal/lower extremity epidural placement

A 
Thoracic: T4-8
Upper abdominal: T6-8
Middle abdominal: T7-10
Lower abdominal: T8-11
Lower extremity: L1-L4

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