Spinals and Epidurals Flashcards
1
Q
How many vertebrae?
A
33 total 7 cervical 12 thoracic 5 lumbar 5 sacral (fused) 4 coccygeal (fused)
2
Q
Describe the vertebral curves in the supine position:
High
Low
A
High - C5, L3
Low - T5, S2
3
Q
What do the ligaments do?
Name them from outer to inner layer.
A
- stabilize vertebral body
- supraspinous, interspinous, ligamentum flavum, (longitudinal, ligamentum nuchae)
4
Q
Where does the ligamentum flavum extend?
What is it made of?
Where is it the thickest?
What is another name for it?
A
- extends from foramen magnum to sacra hiatus
- tough wedge shaped and made of elastin
- thickest in mid-line at L3 (3 mm-5mm in adult)
- “yellow ligament”
5
Q
Describe the cranial meninges and spaces from outer to inner layer.
A
- dura mater - thickest, extends from foramen magnum to S2
- subdural space
- arachnoid mater - physiologic barrier for drugs between epidura space and spinal cord
- subarachnoid space - contains CSF (spinal block) and nerve roots
- pia mater - adherent to spinal cord
6
Q
Where does the spinal cord extend and end?
How many spinal nerves?
A
- extends from foramen magnum to conus medullaris (L1-L2)
- 31 pairs
7
Q
Which part of nerve root is sensory/motor?
A
dorsal/ventral
8
Q
What is a segment?
dermatome?
A
part of spinal cord that gives rise to rootlets of one spinal nerve = segment
dermatome is skin innerv by 1 spinal nerve and its segment
9
Q
Describe cutaneous distribution of T4, T6, T8, T10
A
- nipple
- xiphoid
- last rib
- umbilicus
10
Q
What dermatome location would be concerning for potential losso f sensation of breathing?
A
C7/C8 (last 3 fingers)
11
Q
How much CSF in SA space?
A
150 ml
12
Q
How often is CSF replaced?
A
3-4x/day
13
Q
What is the rate of production for CSF? Where is it made?
A
21 ml/hr by choroid plexus
14
Q
What is the specific gravity of CSF?
A
1.004-1.008
15
Q
What provides blood supply to the spinal cord? (3)
A
- anterior spinal artery
- posterior spinal arteries
- radicular artery
16
Q
What occurs in a SAB (Spinal)?
A
local anesthetic injected in CSF
17
Q
What occurs in epidural anesthesia?
A
local anesthetic injected into epidural or caudal space
18
Q
What is the goal of a neural blockade?
A
sensory (block painful stimuli) and motor (block skeletal muscle tone) blockade
19
Q
Describe a neural blockade site.
A
Site: nerve root but can occur at any and all points along neural pathway from drug site to interior cord
20
Q
What does a centroneuraxial blockade block? What is the goal? What happens to autonomic and motor function?
A
- all impulses regardless of fiber type (nociceptive, motor, proprioceptive, autonomic)
- block NOCICEPTIVE (pain)
- autonomic and motor function are blocked
21
Q
What are advantages of neuroaxial anesthesia?
A
- decreased metabolic stress response to surgery compared to GA
- avoid airway instrumentation
- decreased post-op nausea
- less intra-op sedation
- post-op pain relief
- allows pt to remain awake for C-section
22
Q
What are the disadvantages of neuroaxial anesthesia?
A
- hypotension (ANS)
- slower case start is difficult placement
- failure rate depends one experience
23
Q
What would you consider when choosing a regional technique?
A
- anatomy
- age
- pregnancy
- patho
- sensory level of anesthesia required vs physiologic s/e of regional anes
- consider length of procedure, post-op analgesia, co-existing dz
24
Q
What are indications for SAB/Epidural?
A
- anesthesia (can be alone, combined with GA)
- analgesia (postop, L&D)
25
What are absolute contraindications for SAB/epidural?
- pt refusal
- infection at injections ite
- increased ICP
- anticoag therapy
- severe hemorrhage or hypovolemia
- CNS disease or meningitis
- inability to cooperate/remain still
- bacteremia/septicemia
26
What are CV physiologic changes that can occur with a neuraxial block?
- dependent on spread of blockade and ANS
- venous dilation > arterial dilation
- SVR decreases 15-25% age dependent
- CO decreases 10-15%
- HR decreases T1-T4 (cardioaccelerators), unopposed vagal, decreased stimulation of RA barroreceptors
- MAP decreases
27
What are pulm physiologic changes that can occur with a neuraxial block?
- low blockade levels have minimal pulm effect
- as blockade ascends, accessory muscle paralysis occurs causing weakened breathing and coughin
- no DIRECT resp effects except r/t positioning unless it is a high blockade (C3-C5 = phrenic)
- w/ profound hypotension may have ischemia of central resp centers causing resp arrest
28
What are GI/renal physiologic changes that can occur with a neuraxial block?
- n/v
- hyperperistalsis (unopposed PSNS)
- flow to liver is BP dependent
- maintenance of MAP (no untoward liver effects)
- renal blood flow is autoregulated
- bladder dysfunction - urinary retention, avoid excessive IVF if no catheter
29
What are metabolic/endocrine physiologic changes that can occur with a neuraxial block?
- blocks stress response to surgery
- catecholamine release blocked from adrenal medulla
- cortisol secretion delayed
- shivering = altered thermoregulation with vasodilation
30
What are the pt positions for neuraxial blocks?
- lateral decubitus = forehead to knees, thighs flexed up to abd
- sitting = low lumbar/sacral block, improved midline anatomy
31
What would you do for a pre-procedure prep prior to SAB/epidural?
- monitors
- IVF bolus
- airway and resuscitation equipment
- ER drugs drawn and available
- consider preprocedure sedation
32
Describe the 2 types of SAB needles.
1. pencil point aka Sprotte
-spreads dural fibers and reduced puncture headache
-"pops" as penetrates dura
-greater tip strength to minimize bending/breaking
-side-hole eneables directional flow of anesthetic and reduces possible straddling dura
-tracks straight as it advances thru
2. cutting needle aka quincke
-sharper tip, no "pop"
-increased risk of postdural puncture headache due to trauma to dura
introducer may not be necessary
33
Discuss the SAB approach/technique.
Median - needle or introducer placed midline, perpendicular to spinous processes, aim slightly cephalad
34
Describe the tissue layers when using a midline approach.
- skin
- SQ
- supraspinous lig
- intraspinous lig
- ligamentum flavum
- epid space
- dura mater
- subdural space
- arachnoid mater
- subarachnoid space
(-pia mater, -spinal cord)
35
What are the anatomical landmarks for SAB?
- identify L2-L3, L3-L4, L4-L5
| - palpate sup iliac crests and L4
36
List the 3 epidural insertion sites
1. thoracic
2. caudal
3. lumbar
37
Where is the epidural space the widest? What is in the epidural space?
- L2 = 5mm
| - potential space filled with fat, blood vessels
38
Landmark for epidural?
???
39
What are the tissue layers for a lumbar epidural.
- skin
- SQ
- supraspinous
- interspinous
- ligamentum flavum
- epidural space
40
What is density?
weight in g of 1 ml of solution at specific temp
41
What is specific gravity?
ratio of density of solution compared to density of water at constant temp
42
What is baracity?
density of solution compared to density of other solution
43
What is hyperbaric solution?
LA mixed with dectrose; heavier than CSF, flow down
44
What is hypobaric solution?
LA mixed with sterile water; lighter than CSF, flow up
45
What is isobaric solution?
LA mixed with CSF; equal to CSF
46
What affects the spread of LA in SAB?
-baricity of LA solution
-position of pt
-concentration and volume of LA
-level of injection
(-barbotage/rate of injection, needle/bevel direction)
47
What factors influence block height?
- dose
- site of injection
- baracity
- position of pt
48
What should be considered when dosing SAB?
- surgical site
- length of procedure
- body size (ht/wt)
- physiology
49
When can pt be d/c'd to floor or home?
- PACU to floor after 4 dermatome regression,
50
What should be done before administering an epidural block?
- aspirate and give test dose prior to injection/use incremental dosing
- LA = large volume in a dilute solution for wide segmental spread?
51
What is the dosing for epidural?
LA = 1.25-1.6 ml per segment
52
What are complications of SAB/epidural?
- hypotension
- bradycardia
- sudden cardiac arrest
- n/v
- IV injection
- intrathecal injection
- catheter shearing
- post-dural puncture h/a
- high blockade
- inadequate blockade
- neuro complications
- backache
- infection (septic meningitis)
- urinary retention
- epidural hematoma
53
Who is at highest risk for post dural puncture h/a? And what causes increased risk for PDP h/a?
- younger, white female pts
- larger neede size
- pregnancy
- dehydration
- using cutting tipped needles
- multiple puncture attempts
54
What causes post dural puncture h/a? What is the incidence rate? When does it occur?
- d/t decrease ICP with compensatory cerebral vasodilation
| - occurs w/in 1 day to 1 week of block
55
How do you treat a post dural puncture h/a?
- bedrest
- hydration
- oral analgesics
- ABD binder
- epidural saline injection
- caffeine
- epidural blood patch
56
What is an epidural blood patch?
-forms a clot of leaking meningeal hole
57
How do you perform epidural blood patch?
| What are s/e?
- asceptic autologous blood draw of 10-20 ml
- asceptic epi injection of auto blood into epi evel (at same level or more caudad)
- backache, radicular pain
58
What is the efficacy of epidural blood patch for PDP h/a?
> 90% effective
59
What causes an epidural hematoma?
coagulation defect
60
What are symptoms of epidural hematoma?
numbness or LE weakness
61
What do you do if hematoma is suspected?
- consult NS immediately, 6-8 hrs before perm injury
| - >8 hrs = decrompression may be less successful
62
When should LMWH be held with an epidural placement?
-hold LMWH 10-12 hours pre-placement and post surgical procedure
63
What are s/s of LA toxicity?
- neuroligic: circum-oral numbness, tinnitus, vision changes, dizziness, slurred speech, restlessness, muscle twitching
- seizure followed by CNS depression, apnea, hypotension
- transient radicular irritation
- cauda equina syndrome
