Spinals and Epidurals

Question 1

Describe the vertebrae

Answer 1

33, building blocks of the spine
7 cervical
12- thoracic
5 lumbar
5 sacral (fused)
high curves: C5 L3
Low curves: T5 S2

Question 2

Ligaments of the spine

Answer 2

Purpose is to stabilize vertebral body

1. Supraspinous- think
2. Interspinous- touches the tips of spinous processes
3. Ligamentum flavum- thick and deep right before ED space
4. Longitudinal- behind vertebral body
5. Ligamentum nuchae

Question 3

Describe Ligamentum flavum

Answer 3

Extends from the foramen magnum to the sacral hiatus, extends down entire back, tough ligament made of elastin, thickest at midline L3, 3-5mm, “yellow ligament” Varies in thickness down spine

Question 4

Describe the spinal meninges

Answer 4

Protective membranes continuous with cranial meninges

Arachnoid, dura, pia

Question 5

Describe the Dura Mater

Answer 5

Thickest meningeal tissue
begins at foramen magnum and ends at S2
Abuts the arachnoid mater (subdural space)

Question 6

Arachnoid mater

Answer 6

Primary physiological barrier for drugs to cross epidural to spinal cord
Abuts the pia mater (subarachnoid space)

Question 7

Subarachnoid space

Answer 7

Contains CSF, where we deliver “spinal”, continuous with the cranial CSF to reach brain, houses the spinal nerve roots and rootlets

Question 8

Pia mater

Answer 8

Adheres to the spinal cord

Question 9

Describe the spinal cord

Answer 9

Foramen magnum to conus medullaris, L1-L2, gives rise to 31 pairs of spinal nerves, roots (sensory and motor) roots comprised of rootlets. We try to hit posterior root (sensory) but we get motor. Dorsal roots are very large, greater surface area, easier blocked. Anterior motor root smaller.
Dural sac ends at S2

Question 10

What are dermatomes?

Answer 10

Portion of spinal cord that gives rise to rootlets of a single spinal nerve is called segment. Dermatomes is the skin area innervated by a spinal nerve and its segment.
T4 (nipple), t6 (xiphoid), T8 (last rib), T10 (umbilicus)

Question 11

Describe the physiology of a neural blockade

Answer 11

Local anesthetic bathes the nerve roots in that space.
Subarachnoid (spinal) local anesthetic into CSF
Epidural (or caudal)- LA injected into epidural or caudal space
Overall goal is sensory blockade, we get inadvertent motor
*blockade can occur at an point and all points along neural pathway. from site of drug admin to interior of cord.

Question 12

Describe the physiology of a neural blockade PART 2

Answer 12

Blocks all impulses regardless of fiber type: nociceptive, motor, proprioceptive, autonomic
Autonomic is also blocked, but goal is to do nociceptive fibers

Question 13

Benefits of neuroaxial blockade

Answer 13

decreased metabolic stress to surgery or anesthesia compared with GA
avoids airway instrumentation
Decreases post op N/V
less intraop sedation required
Post-op pain relief
Allows patient to remain awake during C section

Question 14

Disadvantages of neuroaxial blockade

Answer 14

Hypotension, slower case start if placement is difficult, failure rate depends on experience, urban legends

Question 15

Considerations for choosing a regional technique

Answer 15

Anatomy: scoliosis, contractures, BMI
Age: affects dose, increased age means lower dose req.
Pregnancy- reduced volume in epidural space, compression of vena cava can decrease CO
pathophysiology: valve disease

Question 16

Indications for SAB vs Epidural

Answer 16

sensory level of anesthesia required vs. adverse physiological effects of regional anesthesia, ex. severe COPD, needs muscles to expire (thoracic)
Consider length of surgery, post-op analgesia needs, co-existing diseases; combined SAB with CLE, or combo GA/RA (major abdominal cases, lower extremity vascular cases); used for analgesia postop or for L and D.

Question 17

Absolute contraindications for spinal block

Answer 17

Patient refusal
infection at injection site
coagulopothies
severe hypovolemia/hemorrhage
CNS disease or meningitis
Hysteria
Bactermia or septicemia

Question 18

Cardiovascular effects

Answer 18

effects depend on spread and blockade of the ANS. Venous dilation > arterial
SVR (15-25 %) and CO (10-15%) decreases
HR decreases as T1-T4 contain cardioaccelerators, unopposed vagal and decreased atrial baroreceptors.
MAP decreases

Question 19

Pulmonary effects

Answer 19

low levels of blockade have minimal effect
As block ascends, accessory muscle paralysis occurs. No direct effect unless a high blockade, C3-C5 is phrenic.
With profound hypotension might see ischemia of central respiratory centers causes respiratory arrest

Question 20

GI/Renal effects

Answer 20

N/V, hyperperistalsis, flow to liver is BP dependent so must maintain MAP, renal blood flow is auto regulated tho, bladder urinary retention, avoid excessive IV fluids

Question 21

Metabolic/Endocrine effects

Answer 21

Blocks the stress response to surgery, catecholamine release blocked from adrenal medulla, cortisol secretion delayed, shivering, altered thermoregulation with vasodilation

Question 22

Positioning

Answer 22

Positioning is crucial
Lateral decubitus- forehead to knees, thighs flexed to abdomen
Sitting: low lumbar sacral block, improves midline anatomy
R hip fracture, R hip down for gravity’s effects

Question 23

Spinal anesthesia needle types

Answer 23

Pencil point needles (sprout)- designed to help spread the fibers and reduce PDPH, feel a pop as point punctures dura, increased tip strength
Cutting needle (Quincke)- dural pop is less likely, increased risk of PDPH d/t trauma to dura

Question 24

What are the needle approach techniques?

Answer 24

Median- most common approach needle or introducer is placed midline, perpendicular to spinous process, slightly cephalid*
Paramedian- indicated in patients who cannot flex, needle placed 1.5cm laterally and slightly caudad.*

Question 25

What are the two approaches to the epidural placement?

Answer 25

LOR- needle advanced until the interspinous ligament, glass syringe attached.
Hanging drop method- needle advanced until interspinous ligament, then a drop of solution is placed in hub of needle.

Question 26

What are the sites for epidural insertion (3)

Answer 26

thoracic, caudal, lumbar

Question 27

How far will you insert the epidural catheter?

Answer 27

2-3 cm in epidural space, 4-6 cm in epidural space

In the lumbar area, ligamentum flavum is 4cm from skin, 5-6 mm thick in lumbar region.

Question 28

Describe the epidural space

Answer 28

Widest point is at L2, 5mm, contains fat and blood vessels, closed space, medication and catheter is deposited into a potential space

Question 29

Describe the ligamentum flavum

Answer 29

Depth from skin is 4 cm, (80% of people is between 3.5-8 cm) thickest in the lumbar region at 5-6 mm thick.

Question 30

What factors affect the spread of spinal anesthesia

Answer 30

Density- weight in grams of 1 ml of a soution at a specified temperature
Specific gravity- ratio of the density of the solution to another substance’s density
Baracity- density of a solution to the density of another substance
Depends on if the solution is hyperbaric, hypobaric, isobaric
*position, concentration, level of injection, rate of injection, direction of needle and bevel
*height affected by dose, site of injection, baracity, position of patient

Question 31

Describe baracity and it’s effects

Answer 31

The specific gravity of a solution can be altered by the addition of dextrose/water.
Hyperbaric addition of dextrose, LA settles independent areas
Hypobaric- mix LA with sterile water, (hemhroid surgery)
Isobaric- mix local anesthetic with CSF
CSF= 1.004-1.008

Question 32

Things to consider when dosing spinal blocks

Answer 32

Surgical site, length of procedure, body size (height and weight) physiology

Question 33

When can the patient be discharged?

Answer 33

Can go to PACU after a 4 dermatome regression <T10, stable and comfortable
Can go home after ambulation and void, without orthostatic changes

Question 34

Spread of the epidural block depends on what? and what is dosing?

Answer 34

Volume and concentration, you give a large volume of a dilute solution. 1.25-1.6 ml of LA per segment

Question 35

Describe the caudal block

Answer 35

Involves delivery of local anesthetic to the epidural space via injection through the sacral hiatus, landmarks:
sacral cornu
Posterior superior illiac spine
Sacral hiatus

Question 36

what are the indications and limitations of a caudal block?

Answer 36

Indications: pediatric post op pain, hypospadious, inguinal hernia repair, peri area surgeries
Limitations: variable anatomy in adults, high risk of injection to venous plexus, difficulty maintaining sterility

Question 37

Complications of Spinal/Epidural/Caudal?

Answer 37

Hypotension, bradycardia, sudden MI, NV, IV injections, intrathecal injections, catheter shearing, postural puncture headache, high blockade, neurologic complications, inadequate blockade, back ache, meningitis, urinary retention
*EPIDURAL HEMATOMA

Question 38

PDPH increased incidence?

Answer 38

Young, caucasion, female, large needles, pregnancy, dehydrated, cutting tip needle, multiple puncture attempts
1-4% incidence, occurs one day to one week, treatment is bed rest, hydration, oral analgesics, abdominal binder, saline or blood injection ,caffiene

Question 39

Epidural blood patch

Answer 39

Forms a clot over the meningeal hole, 10-20ml of autologous blood draw, inject at epidural level at same level or below, >90% effective, side effects back ache and radicular pain

Question 40

Epidural hematoma

Answer 40

Primary causeis coagulation defect, can have numbness or lower extremity weakness, consult neurosurgery within 6-8 hours, hold LMWH 12 hours before the placement of epidural and 12 hours after the surgery .

Question 41

Local anesthetic toxicity

Answer 41

Neurologic symptoms, circumoral numbness, tinnitus, vision changes, dizziness, restlessness, muscle twitching, seizures, CNS depression

• transient radicular irritation
• cauda equina syndrom (often caused by continuous infusion)