Unit 8 - Neuraxial Anesthesia Pt 2 Flashcards
coagulopathic states that make neuraxial anesthesia contraindicated
- Plt < 100,000
- PT, aPTT, or bleeding time 2x normal value
- Risk epidural or spinal hematoma
why is increased ICP a potential contraindication to neuraxial anesthesia
- increased chance of brain herniation with sudden change in CSF pressure
- Sudden change in CSF pressure by passing a needle through dura
why is sepsis a relative contraindication to neuraxial anesthesia
- Introduction of contaminated blood beyond blood-brain barrier
- Worsening hypotension d/t neuraxial sympathectomy
valvular lesions with fixed SV that may make neuraxial contraindicated
- severe AS
- severe MS
- HOCM
why is difficult airway a relative contraindication to neuraxial anesthesia
- block failure may require rapid conversion to GA
- RAS depression is common and may cause sedation
- Supplementation with IV sedatives may lead to airway obstruction or collapse
why is a full stomach a relative contraindication to neuraxial anesthesia
- hypotension & brainstem hypoperfusion r/t sympathectomy can cause N/V
- Can lead to aspiration if sedated patient has full stomach
why is neuraxial anesthesia often avoided in patients with peripheral neuropathy
- theory that these patients are more susceptible to injury
- Slower to recovery from injury
Data lacking but legal word has a strong opinion
neuraxial considerations in pts with multiple sclerosis
- epidural is safe, spinal might exacerbate s/s
- if spinal would benefit pt, inform about small risk of exacerbation
why should lower dose and concentration of LA be used for neuraxial if pt has multiple sclerosis
Demyelinated fibers may be more susceptible to LA-induced neurotoxicity with spinal
neuraxial considerations in pts with spina bifida
- Increased risk for traumatic injury during needle placement depending on extend of defect
- Greatest risk: neural tube defects, tethered cord
is previous back surgery a contraindication to neuraxial
nope
is a lower back tattoo a contraindication to neuraxial
theoretical concern of introducing neurotoxic compounds into body (no data to justify)
cutting tip spinal needles
Quincke
Pitkin
pros and cons of cutting tip spinal needles
pros: requires less force
cons:
* Higher risk PDPH
* Less tactile feel
* Needle more easily deflected
* More likely to injure cauda equina
non-cutting tip spinal needles - pencil point
Sprotte
Whitacre
Pencan
rounded bevel tip spinal needle
Greene
pros of non-cutting tip spinal needles
- Lower risk PDPH
- More tactile feel
- Needle less likely to deflect
- Less likely to injure cauda equina
needle angles of epidural needles
Crawford = 0 degrees
Hustead = 15 degrees
Tuohy = 30 degrees
why is aortic stenosis a relative contraindication for neuraxial anesthesia
fixed afterload makes CO highly dependent on preload, which decreases with sympathectomy
distance from epidural space to skin in lumbar region of most adults
3-5 cm
Distance ↑ in pregnant & obese patients: skin to epidural space up to 9 cm
optimal depth of epidural catheter insertion
3-5 cm inside epidural space
consequences of epidural catheter depth too shallow vs. too deep
o Too shallow = higher incidence of inadequate analgesia (epidural failure)
o Too deep = catheter may enter epidural vein or exit through intervertebral foramen
distance from ligamentum flavum to dura
~7 mm
(can range from 2 mm – 2.5 cm)
distance from ligamentum flavum to dura
~7 mm
(can range from 2 mm – 2.5 cm)
how does Tuohy needle decrease risk of dural puncture
30 degree curvature + blunt tip
distance from skin to ligamentum flavum
~ 4-6 cm
dermatomes blocked with caudal approach to epidural space
sacral, lumbar, & lower thoracic dermatomes
use of caudal blocks
- Useful for procedures requiring up to a T10 sensory block
- Most commonly used in pediatrics
- Procedure examples: hemorrhoidectomy, labor pain, anal fistula
absolute contraindications to caudal block
spina bifida, meningomyelocele of sacrum, meningitis
relative contraindications to caudal block
pilonidal cyst, abnormal superficial landmarks, hydrocephalus, intracranial tumor, progressive degenerative neuropathy
why are caudal blocks infrequently used after childhood
sacral anatomy more difficult to identify & lumbar approach to epidural space is easier & equally effective
positions for caudal block placement
- Simm’s position (lateral, hips flexed, top leg flexed > bottom)
- prone (small roll under iliac crests, legs in frog position)
landmarks for caudal block
Use posterior superior iliac spines & sacral hiatus as landmarks to envision equilateral triangle with apex of triangle at sacral hiatus
needles used for caudal block
22g needle
25g needle
20g IV catheter
needle insertion for caudal block
bevel up through sacral hiatus at 45-degree angle aiming cephalad
what signifies entry into epidural space with caudal block
advance until you feel a pop
From here, drop angle and advance into epidural space
ligament punctured in caudal block
sacrococcygeal ligament
what increases risk of dural puncture with caudal block
Placing needle tip beyond S2-S3
should LOR with air be used for caudal block?
not in children - increases risk of air embolism
what does resistance to injection suggest with caudal block
needle tip in subperiosteal area
Which spinal ligament must be breached regardless of approach or type of neuraxial block being performed?
ligamentum flavum
—left off on dosing for caudal block pg 18–
nerve roots that are most resistant to effects of LAs
L5
S1
largest spinal nerves
L5
S1
