neuraxial blocks Flashcards
ID these structures
ID atlas and axis on cervical vertebrae
what kind of curves are found on the vertebral column (2 types)
cervical and lumbar lordosis
thoracic and sacral kyphosis
how many vertebrae
33 (7 c, 12 t, 5 l, 5s, 4c)
outline these structures
pedicle
superior articular process
transverse process
spinous process
inferior articular process
vertebral body
atlas (C1) anatomy
lateral masses
transverse foramen
anterior tubercle
anterior arch
superior articular faucet
posterior arch
posterior tubercle
axis (C2) anatomy
odontoid process (dens)
vertebral body
superior articular facet joint
lamina
spinous process
ID these two structures
the spinal nerves exit the vertebral column via the
vertebral foramina
ID the facet joint
ID these critical land marks
another name for tuffiers line (L4)
intercristal line
in infants up to 1 year, tuffiers (intercristal) line correlates with
L5-S1
sacral hiatus
coincides with
results from
is covered by
provides entry point to
coincides with S5
results from incomplete fusion of laminae at S5 and sometimes S4
is covered by sacrococcygeal ligament
provides entry point to epidural space, which is useful in pediatrics
sacral cornua
what is it
what does it result from
bony nodules that flank the sacral hiatus
results from incomplete development of facets
ID these structures
ID these structures
conus medullaris
its where ______ ends
adults: ends at
infants:
where the spinal cord ends
adults: L1-2
Infants: L3
cauda equina
comprised of
located at
bundle of spinal nerves extending from conus medullaris to dural sac
comprised of nerves and nerve roots from L2-S5 nerve pairs and coccygeal nerve
dural sac
significance
adults:
infants:
subarachnoid space that terminates at dural sac
adult: S2
infant: S3
filum terminae
continuation of
extends from
anchors
internal portion extends from
external portion extends from
continue of pia mater caudal to conus medullaris that extends from conus medullaris too coccyx
anchors spinal cords to coccyx
internal portion extends from conus medullaris to external sac
external portion extends from dural sac to sacrum
ID the 5 ligaments and where theyre located in the SC
- supraspinous runs most of the length of the spine and joins the tips of the spinous process
- interspinous ligament travels adjacent to and joins the spinous processes
- ligamentum flavum: 2 that run the length of the spinal canal. they form dorsolateral margins of epidural space. thickest in lumbar region
- posterior longitudinal ligament: travels along the posterior surface of the vertebral bodies
- anterior longitudinal ligament: attaches to anterior surface of vertebral bodies and runs entire length of the spine. also attaches to annulus fibrosus of intervertebral discs
what ligaments do you pass through during midline approach
supraspinous
interspinous
ligamentum flavum
what ligaments do you pass through during paramedian approach
ligamentum flavum
for paramedian, you insert the needle
15 degrees off midline or
1cm lateral and 1cm inferior to interspace
ID these spaces
cranial border of epidural space
foramen magnum
caudal border of epidural space
sacrococcygeal ligament
anterior border of epidural space
posterior longitudinal ligament
lateral border of epidural space
vertebral pedicles
posterior borders of epidural space
ligamentum flavum
vertebral lamina
LA injection into subdural space will cause
high spinal if using epidural dosing, failed spinal if using spinal dosing
target region when performing spinal
subarachnoid space because its got all the goodies (CSF, nerve roots, rootlets, SC)
how many paired spinal nerves in SC
31
ID dorsal, lateral, ventral horn
dermatomes:
spinal nerve root C6
cutaneous innervation
1st digit (thumb)
dermatomes:
spinal nerve root C7
cutaneous innervation
2nd and 3rd digits
dermatomes:
spinal nerve root C8
cutaneous innervation
4th and 5th digits
dermatomes:
spinal nerve root T4
cutaneous innervation
surgeries where you need this level of coverage
nipple line
upper abdominal surgery
c section
cystectomy
dermatomes:
spinal nerve root T6
cutaneous innervation
surgeries where you need this level of coverage
xiphoid process
lower abdominal surgery
appendectomy
dermatomes:
spinal nerve root T10
cutaneous innervation
surgeries where you need this level of coverage
umbilicus
total hip
vaginal delivery
TURP
dermatomes:
spinal nerve root T12
cutaneous innervation
pubic symphysis
dermatomes:
spinal nerve root L4
cutaneous innervation
anterior knee
surgeries where you need this level of coverage: L1-L3 (inguinal ligament)
LE surgery
surgeries where you need this level of coverage: L2-3
foot surgery
surgeries where you need this level of coverage S2-5
hemmrhoidectomy
upper thoracic epidural indications
dosing guidelines
T2-6 upper thoracic
thoracotomy, TAA, breast surgery
5-10mL LA
lower thoracic epidural indications
spread
dosing guidelines (mL LA)
T6-L1 lower thoracic (T1-L4 spread)
gastrectomy, esophagectomy, pancreatectomy, hepatic resection
10-20mL LA
lumbar epidural indications (2)
insertion, spread
dosing guideliens
L2-5 insertion, (T8-S5 spread)
total hip, total knee
20mL LA
do thoracic epidurals help decrease PPC’s
yeh boi
when thoracic epidural is coupled with GA, cardiopulmonary considerations include a higher risk of
bradycardia (block of cardioaccelerator nerves T1-4)
HoTN (decreased CO and vasodilation)
changes in aw resistance (increased vagal influence on airways)
in the subarachnoid space, the primary site of LA action is on
myelinated preganglionic fibers of nerve roots
during an epidural, what does the LA have to do to get to the site of action
diffuse through dural cuff and leak through intervertebral foramen to enter paravertebral area
spinal anesthesia: controllable and non controllable factors that DO affect spread
-controllable:
baricity
patient position during and after block placement
dose
site of injection
non controllable:
volume and density of CSF
spinal anesthesia: factors that DO NOT affect spread
barbotage
increased intra abdominal pressure (coughing, labor)
speed of injection
orientation of bevel
addition of vasoconstrictor
weight
gender
epidural anesthesia: controllable and non controllable factors that DO affect spread
-controllable:
LA volume (most important)
level of injection (most important procedure related factor)
LA dose
-non controllable:
-pregnancy
-old age
epidural anesthesia: factors that DO NOT affect spread
additives
direction of needle orifice
speed of injection
first, second, third TYPE of fibers blocked in order
ANS first (highest block as well)
sensory second (higher than motor block)
motor last
spinal: sensory block is how many dermatomes above motor block
2
spinal: autonomic block is how many dermatomes above sensory blok
2-6
epidural: sensory and ANS are how many dermatomes above motor block
2-4
is there an autonomic differential blockade with epidural anesthesia
no
monitoring sensory block: first, second, last things to go
first: temperature (alcohol pad)
second: pain (pinprick)
last: sense of touch or pressure
monitoring motor block: modified bromage scale (only for lumbosacral nerves)
0= no motor block
1=patient cannot raise extended but can move knee and feet
2= cannot raise extended leg or move knee but can move feet
3=complete motor block (cannot move knee, leg, feet)
A alpha
myelination
function
diameter
velocity
block onset
myelination: heavy
function: skeletal muscle: motor proprioception
diameter: 12-20
velocity: +++++
block onset: 4th
A beta
myelination
function
diameter
velocity
block onset
myelination: heavy
function: touch, pressure
diameter: 5-12
velocity: ++++
block onset: 4th
A gamma
myelination
function
diameter
velocity
block onset
myelination: medium
function: skeletal muscle- tone
diameter: 3-6
velocity: +++
block onset: third
A delta
myelination
function
diameter
velocity
block onset
myelination: medium
function: fast pain, temp, touch
diameter: 2-5
velocity: +++
block onset: 3rd
B
myelination
function
diameter
velocity
block onset
myelination: light
function: preganglionic ANS fibers
diameter: 3
velocity: ++
block onset: first
C sympathetic
myelination
function
diameter
velocity
block onset
myelination: 0
function: postganglionic fibers
diameter: .3-1.3
velocity: +
block onset: second
C dorsal root
myelination
function
diameter
velocity
block onset
myelination: 0
function: slow pain, temp, touch
diameter: .4-1.2
velocity: +
block onset: second
bupivicaine 0.5-0.75% spinal dose dose to get to
T10
T4
onset
T10: 10-15mg
T4: 12-20mg
onset 4-8m
levobucaine 0.5% (no dextrose)
spinal dose dose to get to
T10
T4
onset
T10: 10-15mg
T4: 12-20mg
onset 4-8m
ropivicaine 0.5-1% (with or without dextrose) spinal dose dose to get to
T10
T4
onset
T10: 12-18mg
T4: 18-25mg
onset 3-8m
2- chlorprocaine 3% (with or without dextrose) spinal dose dose to get to
T10
T4
onset
T10: 30-40mg
T4: 40-60mg
onset 2-4m
tetracaine 0.5-1% (with dextrose) spinal dose dose to get to
T10
T4
onset
T10: 6-10mg
T4: 12-16mg
onset 3-5m
initial volume dosing for epidural
1-2mL for very level to be blocked
top off epidural dosing
50-75% of original dose and should be administered before recession of 2 dermatomes
drug for epidural: chlorprocaine
concentration
onset
DOA
concentration 3%
onset: 5-15m
DOA: 30-90m
drug for epidural: lidocaine
concentration
onset
DOA
concentration 2%
onset 10-20m
DOA 60-120m
drug for epidural: ropivicaine
concentration
onset
DOA
concentration: 0.1-0.75%
onset: 15-20m
DOA: 140-220m
drug for epidural: bupivacaine
concentration
onset
DOA
concentration: 0.0625-0.5%
onset: 15-20m
DOA: 160-220m
drug for epidural: levobupivacaine
concentration
onset
DOA
concentration: 0.0625-0.5%
onset: 15-20m
DOA: 150-225m
water
density
SG
baricity
density: 0.9933
SG: 1
basicity: 0.9930 (in r/t CSF)
CSF
density
SG
baricity
density: 1.003
SG: 1.002-1.009
baricity: 1
basicity of procaine 10% in water
hyperbaric. (because theres so many molecules in a 10% solution)
primary mechanism of anesthetic blockade when neuraxial anesthesia causes sympathectomy
preganglionic B fingers in sympathetic chain
how neuraxial anesthesia affects the following CV parameters:
peload
afterload
CO
HR
preload decreased d/t sympathectomy
afterload decreased d/t sympathecctomy
CO variable (decreased VR that lowers CO but also decreased SVR to help CO)
HR variable: decreased VR which activates Bezold Jarisch reflex (unloading from mechanoreceptors) which decreases HR/can cause asystole.
reverse Bainbridge reflex-unloading of stretch receptors in SA
apnea r/t neuraxial anesthesia
-not the result of phrenic nerve paralysis or high concentrations of LA in CSF.
-its usually a result of brainstem hypo perfusion
neuraxial anesthesia and accessory respiratory muscle function
decreased fx of accessory muscles which has no effect on a healthy person but does have an effect on people who have COPD or so. so, if this comes up on the exam, YES neuraxial anesthesia does have an effect on resp mechanics (insp AND exp)
CNS and neuraxial anesthesia
decreased perfusion to RAS which can cause drowsiness
GI and neuraxial anesthesia
neuraxial LA’s decrease SNS tone and increases PSNS which relaxes sphincters and causes peristalsis
kidneys, liver, and neuraxial anesthesia
so long as SBP is maintained, hepatic and renal BF and function are not altered
neuraxial opioids inhibit pain transmission via
(where)
(how)
substantia gelatinosa (rexed lamina 2 in dorsal horn)
decreased cAMP, decreased Ca conductance, increased K conductance.
neuraxial opioids do NOT cause (3)
sympathectomy
skeletal muscle weakness
changes in proprioception
list of opioids we use in neuraxial space from most lipophilic to most hydrophilic
sufentanil > fentanyl > meperidine > hydromorphone > morphine
which opioids (hydrophilic v lipophilic) stay in neuraxial space longer and which diffuses out?
hydrophilic stays in CSF for longer time periods
lipophilic doesn’t stay in CSF for a long time and diffuses out into periphery
which opioids (hydrophilic v lipophilic) have extensive versus minimal spread
hydrophilic: extensive, wide band of analgesia, more rostral spread towards brain
lipophillic: minimal, narrow band of analgesia, less rostral spread
site of action of neuraxial opioids (hydrophilic v lipophilic)
rexed lamina 2&3
also systemic for lipophilic
onset and DOA of hydrophilic neuraxial opioids
onset: delayed (30-60m)
DOA: longer (6-24h)
onset and DOA of lipophilic neuraxial opioids
onset: fast (5-10m)
DOA: shorter (2-4h)
which opioids (lipophilic versus hydrophilic) have a higher incidence of n/v and pruritis
hydrophilic has higher incidence
sufentanil
intrathecal dose
epidural dose
intrathecal dose: 5-10mcg
epidural dose: 25-50mcg
fentanyl
intrathecal dose
epidural dose
intrathecal dose: 10-20mcg
epidural dose 50-100mcg
hydromorphone
intrathecal dose
epidural dose
intrathecal dose: NO hoe
epidural dose: .5-1mg
meperidine
intrathecal dose
epidural dose
intrathecal dose 10mg
epidural dose 25-50mg
morphine
intrathecal dose
epidural dose
intrathecal dose 0.25-0.3mg
epidural dose 2-5mg
