Central Neuraxial Blocks

How many vertebrae are in the spine? WHat is the configuration?

33

• 7 cervical- smallest

• 12 thoracic

• 5 lumbar- largest

• 5 fused sacral

• 4 fused coccygeal

How do the angles of apinous processes vary?

• Horizontal: Cervical, Low Thoracic, Lumbar

• Caudad angulation: Thoracic

Name the 4 ligaments of the spinal column and their connections?

• Supraspinous

  • Connects the tips of the spinous processes from sacrum to T₇

• Interspinous

  • Connects the posterior spinous processes & fills gap

• Ligamentum flavum

  • Connects the lamina of the adjacent vertebrae

• Ant/Post Longitudinal

  • Primary supportive ligaments of the vertebral column

  • Binds vertebral bodies and provides stability

Which vetebral landmarks starts at the vertebral prominens and can be felt or seen on most people and can be useful in identifying the midline of the body?

C7-T1

WHich vertebrae lines up with the inferior scapula?

T7

What is Touffier’s line?

line that spans across the iliac crests *superior/posterior) and indicates the target area for spinals (crosses at L4)

Where does the foramen magnum end and the conus medullaris starts?

L1-2

Where does the dural sac terminate AKA filum terminale?

S2

Where does the epidural space run?

foramen magnum to the sacral hiatus (S4-5)

How does a child’s spinal anatomy differ from adults? Why is this important?

the spinal cord terminates at L1-2 in adults

L3 in children- will need to puncture lower to avoid spinal cord (often will utilize a caudal block)

Name the different levels of the spinal cord coverings?

• Pia mater - adherent to the spinal cord & nerves

• Arachnoid - between the pia & dura mater

  • Subarachnoid  - between the arachnoid & pia mater;  Contains CSF

• Dura mater - toughest outer membrane 

  • Epidural space - potential space between dura mater & ligamentum flavum

how many spinal nerve roots are there and what are the different classes?

31 pairs (62 total)

• anterior/vental (motor)

• posterior/dorsal (sensory)

explain the supply of blood to the gray and white matter of the brain? Spinal cord?

• gray: 80cc/100gm/min

• white: 20cc/100gm/min

• Avg 50cc/100 gm/min

• spinal cord- slightly lower (still similar)

Which vessels supply the spinal cord with blood?

1 anterior spinal artery and 2 posterior spinal arteries

CSF is ______ secreted and requires an intact _______

actively; BBB

composition of CSF: Specific gravity, pH, pCO2, normal electrolytes, color, consistency

• Specific Gravity = 1.003-1.008

• pH = 7.3

• pCO2 = 51

• Lytes:

  • ↑ NA+

  • ↓ K+, CA+, HCO3-, Glucose

• Normal color and consistency is the same as water

• ****Key: for a spinal- clear, colorless, water-like solution should return

Commonly seen abnormalities of CSF

• Yellow: xanthochromia

  • caused by bilirubin

  • 5 hr to 1 week post SAH

• Hazy or turbid:

  • Leukocytes or protein

• Bloody: does it clear?

  • May be minimal blood at first, but it should clear

  • If it doesn't clear, assume you are in a vessel

ICP, AKA __________ follow the __________ doctrine which states: ____________

AKA supratentorial pressure

monroe Kellie Doctrine- Blood+ Brain +CSF= ICP

• increase in any will lead to decrease of the others

Normal ICP

5-15 mmHg

Can a subarachnoid block be done if ICP is increased?

No

specific area of skin innervated by a spinal nerve

Dermatomes

Name the key dermatome for each landmark:

• Above collarbone to shoulder

• Skin over the shoulder

• Thumb and lateral forearm

• Middle fingers

• Small finger and medial forearm

• nipple line

• Xiphoid process

• Umbilicus

• Area above groin

• Anterior knee

• Medial malleolus, thigh

• Outside part of the calf, foot, big toe

• Lateral foot, back of leg

• Above collarbone to shoulder-C4

• Skin over the shoulder- C5

• Thumb and lateral forearm- C6

• Middle fingers- C7

• Small finger and medial forearm- C8

• nipple line- T4

• Xiphoid process-T6

• Umbilicus- T10

• Area above groin- L1

• Anterior knee- L3

• Medial malleolus, thigh- L4

• Outside part of the calf, foot, big toe- L5

• Lateral foot, back of leg- S1

specific muscle or muscle group innervated by a single spinal nerve, importnat for US guided blocks with nerve stimulation

myotomes

Name the test for each myotome:

• C5

• C6

• C7

• C8

• T1

• L1-2

• L3-4

• L5-S1

• L5

• S1

Name the nerve root responsible for each DTR:

• biceps

• brachioradialus

• triceps

• quadriceps

• achilles tendon

Explain the main differences between a spinal and an epidural

• spinal- a single injection into the CSF used for the lower half of the body

• epidural- stays outside in the dural space (just past the ligamentum flavum), where no CSF is present and can be used for labor, lower half surgery, or abd surgery

a central neuraxial block is a ________ block that causes peripheral _______ and skin temp _________

sympathetic, vasodilation, elevation

What are the 4 steps of a neuraxial block in order of block onset/ loss of function? (Returned in reverse order)

1. pain and temp sensation (most important)

   1. temp is a cousin to pain

2. proprioception

3. touch and pressure sensation

   1. usually not lost completely (can feel touch/ pressure but no pain)

4. motor

   1. usually not fully blocked

What determines the sequence of loss during a block?

arrangement of nerve fibers in the root (loss of fibers closest to the surface

• B fibers

• C and A delta fibers

• A beta

• A alpha

Explain the different dermatome levels of a differential blockade

ANS>Sensory>motor

• ANS- 2 dermatomes above sensory (estimated)

• Sensory- 2 dermatomes above motor (loss of sensation to pinprick or cold)

• motor- hardest to achieve (movement/ muscle tone)

What could be an issue if your sensory block is at T3?

Your ANS block can be as high as T1 (HR control center) can result in bradycardia

What is a normal pre-procedure fluid management plan for a spinal?

• ½- 1 liter or ~ 15cc/kg is sometimes given

• Probably not effective

• Dependent on your location and their preferences

Which positions are often used for a spinal? Which is better?

sitting vs lateral

• sitting- usually done cross legged, but legs can dangle with stool if needed and arms rest on the knees with chin to chest

  • more common because no torque

What are the 3 approached to a spinal/ epidural?

• midline

• paramedian

  • 1.5 cm lateral to inferior border of spinal process

• Lumbo-sacral/ Taylor’s approach

  • paramedian approach through L5-S1

When is the lumbo sacral/ Taylor’s approach utilized?

usually in elderly arthritic males bc the ligaments at this level do not calcify

Name the layers punctured during a midline approach from external to internal

• Skin

• Sub-Q

• Supraspinous ligament

• Interspinous ligament

• Ligamentum Flavum

• Epidural space (~4-6 cm depth)

• Dura mater

  • Subdural space

    • Block in this area lead to a weird patchy block

• Arachnoid

  • Sub-arachnoid space= CSF

Name the layers punctured during a Paramedian approach from external to internal

• skin

• sub Q

• interspinous??? maybe, but probably not

• flavum

• epidural space

• dura

• subdural

• arachnoid

• subarachnoid

Name the layers punctured during a epidural approach from external to internal

• skin

• sub-Q

• supraspinous

• Interspinous

• Flavum

• Epidrual space

whats the normal depth of an epidural?

4-6 cm