Neuraxial Anesthesia Review Flashcards
what is the most prominent cervical process
c7
what is the inferior tip of scapula
t7
what is the supeerior aspect of the iliac crest
tuffier’s line (L4)
what is the posterior superior iliac spine
s2
what occurs w/epidural spread in OB patients?
increase in spread d/t the engorged epidural veins compressing the dura
where does the spinal cord end?
L1 - L2
what are we targetting for spinal + epidurals?
the nerve roots
what affects the spread during a spinal?
the baricity
what affects the spread during an epidural?
the volume
spinal vs epidural
spinal: single shot, dosage, baricity, patient position
epidural: catheter, volume block
what level do you want for a labor vs c/sx
labor = T10 c/sx = T5/T6
name the absolute contraindications for neuraxial
- refusal
- increased ICP
- coagulopathies
- severe aortic or mitral stenosis
- severe hypovolemia
- infection at the injection site
aortic valve stenosis mild
jet velocity: < 3
mean gradient: < 25
valve area: > 1.5
aortic valve stenosis moderate
jet velocity: 3 - 4
mean gradient: 25 - 50
valve area: 1 - 1.5
aortic valve stenosis severe
jet velocity: > 4
mean gradient: > 50
valve area: < 1
aortic valve stenosis critical
jet velocity: > 5
mean gradient: > 80
valve area: < 0.7
relative contraindications for neuraxial anesthesia (7)
- uncooperative
- allergy (esters- chloroprocaine, procaine, tetracaine)
- anticoagulant or thrombolytic therapy (afibb, DVT, DVT prophylaxis)
- pre-existing neuro deficit
- chronic HA or backache
- severe spinal deformity
- valvular stenosis
minimal pre-procedure monitoring
- PIV
- Suction
- Airway supplies
- monitors (EKG, pulse ox, BP, ETCO2)
- Supportive medications (induction, paralytic, atropine, vasoactive)
what is the most common identifiable interspace
L2 - L3
discuss the difference between Tuohy + Crawford needle
Both are 9 cm w/1 cm increments
- Tuohy = curved, easier
- Crawford = straight, easier to insert, higher rate of dural punctures
What is the distance to ligamentum flavum
4 - 6 cm at the lumbar level
Ligamentum –> dura is another 4 mm
what type of grip w/epidural
bromage grip to advance through supraspinous ligament, interspinous ligament
how to insert epidural needle
bevel cephalad
loss of resistance is the most common method
fill w/2-3 mL of NS
Tuohy + hub =
12 cm
Epidural Catheters
typically two gauges smaller than the needle
open-ended w/multiport (lower incidence of inadequate analgesia but higher incidence of accidental vein cannula)
1 dash = 1 cm
2 dash = 10 cm
thick line = 12 cm
3 dash = 15
how far to advance epidural catheter?
when the thick black mark is flush w/hub, the catheter is flush with the needle tip. slight resistance is noted when the catheter is advanced and the patient might feel a paresthesia
advance 3 - 5 cm past the needle hub
too deep placement of epidural catheter?
puncture of dura
pass into an epidural vein
migration into intervertebral foramen
how to remove the needle for an epidural
slowly withdraw needle over the catheter
once removed- note the depth of the catheter at the skin (if the depth is < 1 cm to epidural space… replace)
epidural test dosee
attach adaptor to the free end
look for blood / csf
aspirate
inject 3 mL of 1.5% lidocaine w/epinephrine 1:200,000
45 mg lido + 15 mcg epi
how do you know if the needle is in the epidural vein
> 20% increase in HR and BP
who performed the first spinal anesthetic
Augustus bier in 1899
what is specific gravity… water? CSF?
the density of a substance compared to the density of water
water = 1 CSF = 1.003 - 1.009
what is baricity
the resting position of two fluids w/different specific gravities when mixed in a single container - this helps the potential spread of LA in the subarachnoid space
isobaric
LA = CSF (i.e. NS)
–> longer effect b/c large volume per area
hyperbaric
lasts 2 hours
LA > CSF
dextrose
hypobaric
sterile water
what primarily influences the LA level during a spinal
baricity, position of patient, drug dose, site of injection
secondary influences on the anesthetic level
patient height pregnant age CSF volume spine curve drug volume intra-abdominal pressure needle direction
patient is supine.. where does hyperbaric LA go
T4 - T8
what is the size of your introducer for a spinal
18G
size of spinal needle
25G (22G if an old person just don’t use introducer)
name the types of spinal needles
cutting vs. pencil point
Gertie Marx (26G)
Sprotte (25G) PP
Whitacre (25G) PP
Quinke (25G) Cutting
what are the two pops of a spinal
ligamentum flavum
dura
what is a continuous spinal
- dura punctured w/17G epidural needle
- an epidural catheter is placed through the dura into subarachnoid space
- small incremental doses of local are given until the desired level achieved (total dose to achieve the desired level is the same)
CSE
Two Step: spinal first (usually just narcotics), epidural placed 1 - 2 levels above
One Step: epidural needle placed, spinal through the epidural needle, intrathecal dose given, catheter placed
CSE concerns
- intrathecal effects on fetus
- cannot ambulate post narcotics
- maternal hypotension + itching
- catheter migration
- high spinal
- metallic particles
- PDPH
- neuro injury
paramedian approach
used when patient cannot flex spine
- history of spine surgery, RA, hip or upper leg trauma
- 1 cm lateral and 1 cm caudal to spinous process
- advance needle toward midline, pass through paraspinous muscles to ligamentum
paramedian passes through what muscles
erector spinae
-ileocostalis, spinalis, longissimus
hit bone early
redirect cephalad
touching the superior crest of spinous process below inteerspace
hit bone late
needle touching inferior surface of the spinous process above interspace
redirect caudal
blood in catheter?
text book answer - withdraw and go one level above
absence of CSF
reinseert stylet
advance 1 - 2 mm
aspirate
esp. important to advance another mm w/pencil point needles
blood tinged vs frank blood
blood-tinged.. just wait a few seconds to see if it clears
frank blood - epidural vein so withdrawal
how is LA metabolized
absorbed into plasma
metabolized via properties
ester = non specific plasma esterases
amide = liver
procaine
ester pka = 8.9 ionized = 97 protein binding = 6 slow onset DOA = 60 - 90m
chloroprocaine
ester
fast onset
DOA = 30 - 60m
tetracaine
ester pka = 8.5 ionized = 93 protein binding = 94 slow onset DOA = 180 - 600m
lidocaine
amide 7.9 76 ionized 64 protein fast onset DOA = 90 - 120
mepivicaine
fast onset, 120-240 DOA
ropivacaine
slow onset
DOA 180 - 600m
bupivacaine
8.1 83 ionized 95 protein slow onset DOA 180 - 600
epinephrine
alpha 1 agonist
0.1 - 0.2 mL of 1:1000 solution
greatest effect w/tetracaine
phenylephrine
more effective than epi
0.05 - 0.2 mL of 1% solution (0.5 - 2 mcg)
clonidine
helps w/tourniquet pain
fentanyl characteristics
by nature, preservative free
highly lipid soluble
binds directly to the lipid elements of the spinal cord
less drug to diffuse systemically
morphine characteristics
duramorph
highly polarized, not very lipid soluble so hangs out in CSF for hours
6-8 hours rises to respiratory center
fentanyl dosing
12.5 - 15 mcg
onset = 5 - 10m
DOA = 2 - 4 hours
morphine dosing
0.1 - 0.25 mg (100 mcg for a c/sx)
onset = 60 - 90m
DOA = 24h
dexmedotomidine
alpha 2 agonist
do not mix w/fentanyl
spinal = 5 mcg epidural = 20 - 50 mcg
great for a one-sided spinal
precedex side effects
profound hypotension if you add an opioid with it prolonged block (4h spinal)
a-alpha fibers
function = proprioceeption, motor
diameter = 6 - 22 um
heavy myelination
last to block
a-beta fibers
touch, pressure
diameter = 6 - 22um
heavy myelination
intermediate block
a-gamma fibers
muscle tone
3 - 6 um
heavy myelination, inteermediate block
a-delta
pain, cold temp, touch
1 - 5 um
heavy myelin, intermediate block
type B fibers
preganglionic autonomic vasomotor
< 3 um
light myelination, early block
type C fibers
sympathetic - postganglionic vasomotor - .3 - 1.3 - early onset
dorsal root - pain, temp, touch - .4 - 1.2 - early onset
NO MYELINATION
WHAT IS THE CARDIAC ACCELERATOR FIBERS
T4
how to evaluate block?
(B FIBERS) sympathectomy 1st
a-delta, c fibers next (light touch, temperature)
a-alpha, a-beta, a-gamma last (touch, proprioception, muscle relaxation)
what is the easiest way to assess level changes
sensory
T4 = nipples
T 10 = bellybutton
c-section we want T4 - T6
autonomic blockade
two dermatomes higher than sensory block
motor is two levels below
post-dural puncture headache
dura compromise
RF = needle size, type, younger, female, pregnant
S/S = bilateral frontal or retroorbital or occipital extending to neck, photophobia, nausea, positional
PDPH treatment
conservative for the first 12 - 24h
-recumbent, analgesics, fluid, caffeine, stool softener, soft diet
BLOOD PATCH
-15 - 20 mL blood, place BELOW puncture site (1 - 2 levels)
