Neuraxial Anesthesia Flashcards by Allison Sass

Neuraxial Anesthesia

Local anesthetic placed around CNS
Includes the following:
- Spinal
- Epidural 
- Caudal
- Regional

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Vertebral Column:
___ Bones
___ Spinal Nerves

33 bones sequentially interconnected
Separated by fibrocartilaginous disks

31 spinal nerves

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Vertebral Bones:
\_\_\_ Cervical
\_\_\_ Thoracic
\_\_\_ Lumbar
\_\_\_ Sacrum
\_\_\_ Coccyx

7 cervical 
12 thoracic
5 lumbar
5 sacrum (fused)
4 coccyx

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Spinal Nerves:
\_\_\_ Cervical
\_\_\_ Thoracic
\_\_\_ Lumbar
\_\_\_ Sacrum
\_\_\_ Coccyx

8 cervical nerve pairs
Only 7 cervical bones
12 thoracic
5 lumbar
5 sacrum
0 coccyx

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Anterior Curvature

Cervical & lumbar

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Posterior Curvature

Thoracic & sacral

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Anatomic Landmarks

Vertebra prominens C7
Inferior scapula angle T7
Tuffier’s line L4-L5 disc

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Lumbarization

L5 & S1 fused

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Sacralization

S1 & S2 fused

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Spinal Structure Order

needle path when placing epidural or spinal

Skin
Subcutaneous tissue & fat
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
Epidural space
Dura
Subarachnoid space

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Supraspinous Ligament

Strong fibrous cord that connects spinous processes at the apex

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Interspinous Ligament

3 layers
Thin & membranous ligament that connects adjoining spinous processes
Limits spinal flexion

Thinner in the lumbar region

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Ligamentum Flavum

Yellow, elastic tissue
Strongest & most posterior
“crunchy”

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Spinal Cord Length

Average 40cm
Men 45cm

Diameter 1cm
Wider in cervical/lumbar regions d/t extremities

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Spinal Cord Layers

DAP →

Dura mater - tough mother, outermost thick
Arachnoid mater - spider web
Pia mater - loving, tender mother

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Dura Mater

Outermost
Tough fibrous layer
Extends from foramen magnum to S2-S3

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Arachnoid Mater

Delicate middle layer
Spider web
Non-vascular
Ends at S2

Subarachnoid Space

B/w pia & arachnoid mater
CSF found here
Spinal anesthesia site - subarachnoid & intrathecal
Local anesthetic spinal target direct proximity to spinal nerves ↓amount/dose

Pia Mater

Tightly bound
Highly vascular
Covers the spinal cord

Spinal Cord Level

Extends to L1-L2 in adults
Place spinal anesthesia BELOW spinal cord level
Less likely to cause damage in cauda equina (only axons no cell bodies)

Longer in children L3
Caudal anesthesia ideal d/t anatomy

Conus Medullaris

Cone shaped spinal cord end

Filum Terminae

1st sacral vertebral soma

Cauda Equina

Horse’s tail
Only nerve axons
Hang freely w/in thecal or dural sac
Less likely to puncture nerve root

Epidural Space

Potential space
Continuous w/in vertebral canal

Contains fat, arteries, veins, lymphatics, & nerve roots

Average distance from skin to lumbar epidural space = ___ cm

5cm 2.5-8cm Dependent on intervertebral space & body habitus Varies based on location w/in vertebral column Lumbar vs. sacral

CSF

Cerebral spinal fluid located b/w pia & arachnoid mater w/in the subarachnoid space Clear, colorless fluid (straw, pale yellow) Selective blood filtrate 1.003-1.009 specific gravity

CSF Function

Mechanical buffer to protect the brain & spinal cord

Total CSF Volume

Adult 150mL Produce 21mL/hr Spinal subarachnoid space holds 20-35mL

Spinal Cord Blood Supply

Arterial distribution: - Segmental arteries - Longitudinal arteries (2/3 anterior x1 & 1/3 posterior x2) Artery of Adamkiewicz (anterior artery supplies distal 2/3 spinal cord) T9-12 - Radicular ``` Venous: - Epidural veins - Valveless plexus - Most prominent lateral Engorged in pregnant & obese patients Venous congestion ↑puncture risk ```

Dermatomes

Cutaneous sensation map Method to determine block functional level Based on embryonic development

Nipple line

T10

Umbilicus

Spinal Anesthesia

One shot Trendelenburg to help LA move upward ↓dosage direct contact w/ spinal nerves

Epidural Anesthesia

Able to titrate medication and potential convert labor pain epidural to C/S epidural ↑LA amount/dose d/t no direct contact w/ spinal nerves

Caudal Anesthesia

Epidural type | Ideal w/ children

Regional Anesthesia

Related to specific region | Shoulder or ankle block

Scoliosis

Lateral spine curvature | Potential to restrict lung expansion

Kyphosis

Excessive posterior curvature or hunchback | Elderly patients

Lordosis

Excessive anterior curvature Obese or pregnant patients Attempt to compensate & maintain gravitational center

Identify & Label Vertebrae

``` Body Pedicle Lamina Transverse process Spinous process Vertebral foramen Intervertebral foramen Superior articulating process Inferior articulating process ```