Neuraxial Flashcards
cardiac accelerator nerves
T1-T4
Phrenic nerves
C345
Spinal anesthesia definition
injection of LA into Subarachnoid space
Dose of prop for induction
1.5 - 2.5 mg/kg
onset spinal vs epidural
spinal = rapid
epidural = slow
spread spinal vs epidural
spinal; higher than expected; may extend extracranially
epidural; as expected can be controlled with volume of LA
nature of block spinal vs epidural
spinal; dense
epidural; segmental
motor block spinal vs epidural
spinal; dense
epidural; minimal
hypotension spinal vs epidural
spinal; likely
epidural; less than spinal
walking epidural
Ropivicain; not very dense, segmental
onset epidural vs spinal
spinal; 5 min
epidural; 10-15 min
duration epidural vs spinal
spinal; limited and fixed
epidural; unlimited
placement level for spinal
L3-L4, L4-L5, L5-S1
Dosage of LA for spinal vs epidural
spinal; dose - based (mg)
epidural; volume- based
Largest dose that can be given for spinal
3 ml
LA toxicity
IV admin of LA ( bupivacaine = most sensitive to the heart)
high risk with epidurals because of veins and volume given
Gravity influence on spinal
spinal = big effect
epidural; no gravity effect
Coag levels that are absolute contraindications for neuraxial
INR > 1.5 (ASRA), some texts > 1.2
Platelets < 100,000; 50,000 Miller; consider trends*
Nagelhout x 2 (PT, aPTT, bleeding time)
Known coagulation disorder or taking anticoagulants
increase risk of hematoma
Valvular disease absolute contraindications for neuraxial
AS < 1.0 cm2 or MS < 1.0 cm2
IHSS (Idiopathic hypertrophic subaortic stenosis)
relative contraindications for neuraxial anesthesia
Deformities of spinal column
Preexisting disease of the spinal cord
Chronic headache/backache
Inability to perform SAB after 3 attempts
Total number of vertebra and how much for each area
33 total
7 cervical
12 thoracic
5 lumbar
5 sacral
4 coccyx
Total spinal nerves and number/ location
31 nerves pairs
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccyx
Distance from skin to ligamentum flavum
4 cm in 50% of pts and 4-6 cm in 80% of pts
The spinal cord ends at…
30% end at T12
60% end in L1
10% end in L3
board answer; L1
Spinal cord ends at….for peds
L3
High and low points while supine
high = C3 and L3
Low = T6 and S2
End of dural sac
S2
end of subarachnoid space
Orientation of lumbar spinous processes
straight/ horizontal
needle = straight
Orientation of Thoracic spinous process
caudally/ oblique
needle = point cephalad / up.
dura matter start and end points
Starts at the foramen magnum, ends in S2 (fuses with filum terminale)
Spinal cord blood vessels
one anterior spinal artery - vertebral artery
2 posterior spinal arteries- inferior cerebellar artery
segmental spinal arteries - intercostal and lumbar arteries
CSF volume
100 to 160 ml
20 -25 ml/hr
entire csf volume replaced q6h
dermatome looks at…
sensory levels
Umbilicus dermatome
T10
Nipple dermatome
T4 (csection height)
Thumb dermatome
C6
Hand dermatome
C6 - thumb
C7- pointer and middle
C8- ring and pinky
Tuffier’s (Intercristal) Line
Line between L3 and L4 interspace and is at or above the level or the superior iliac crest
LA for spinal spreads to the…..
cauda equina and spreads to the nerve roots
Even with epi, whats the longest a spinal will last?
150 min = 2.5 hr
Spinal nerves in subarachnoid space is covered by thin…..
pia layer
factors that influence the decision on which LA to use for Neuraxial anesthesia
Type of sx
Length of sx
Surgeon
shortest acting LA
lidocaine
good for outpt sx
LA structure and difference between Ester and amide
aromatic ring, intermediate link (ester or amide), tertiary amine
opioid adjuncts does what to a blockade
Make “denser”
It intensifies the blockade/ sensation
Alpha 2 agonist adjunct with neuraxial blockade
Improves Density, duration, and analgesia
Vasopressor effect as an adjunct with neuraxial blocks
Extends duration only; No effect on density or analgesia
Epinephrine (good IV marker epidurals: initial bolusing)
Causes vasoconstriction
Epidural morphine dose
3-5 mg (24 hr duration)
epidural fent dose
50 -100 mcg
sufent epidural dose
10-25 mcg
morphine spinal dose
100-400 mcg (24 hrs)
fent spinal dose
10-25 mcg
sufent spinal dose
2.5-10 mcg
opioids spread…
cephalad
hydrophilic and lipophilic opioids
Hydrophilic drugs (morphine)
lipophilic drugs (Fentanyl/Sufentanil)
Hydrophilic drugs slow cephalad spread than lipophilic drugs
side effect of sufent
muscle rigidity
Opioid to use in out pt setting
sufent
incidence of pruritis with opioid use
30-100%
Treatment for Pruritis
benedryl 25-50 mg IV
Nalxone 0.1 mg IV - best
Buprenex (mixed agonist/antagonist)
Prophylaxis for Pruritis
minimize the dose of morphine < 300 mcg (100 mcg)
Ondansetron 4 mg IV
Nubain 2.5-5 mg IV (partial agonist/antagonist)
treatment for nausea
ondansetron (8mg)
Naloxone (0.1 mg)
Phenergan (12.5-25 mg IM)
Epi wash dose
0.2-0.3 mg
Spinal with epi is most profound increase in effect with what med?
Tetracaine
Epi with epidural has the greatest effect in the duration of anesthesia in what meds?
lidocaine, mepivacaine and 2 chloroprocaine
Where is clonidines site of action when given spinal or epidural
substantia gelatinosa
Neo wash dose
2- 5 mcg
tetracaine with epi/ neo effect
profound increase in effect
Spinal dose for Dexmedetomidine
3 mcg
clonidine dose for spinal
15-45 mcg
Factors affecting uptake of LA into neural space
concentration of LA in CSF
Surface are of the nerual tissue
lipid content of the nerve
Blood flow of the nerve
A alpha fiber
propioception and motor
large
heavy mylinated
last to get blocked
A beta fibers
touch, pressure
heavily mylinated
intermediate block onset
A gamma fibers
muscle tone
small
heavily mylinated
intermediate block onset
A delta fibers
pain, cold temperature, touch
small
heavily mylinated
intermediate block onset
B fibers
preganglionic autonomic vasomotor
pretty small
lightly myelinated
early block onset
C sympathetic fibers
Post ganglionic vasomotor
really small
no myelin
early block onset
C Dorsal root fibers
pain, warm and cold temp, touch
really small
no myelin
early block onset
Progression to differential block
B fibers
C fibers
A delta
A gamma
A beta
A alpha
Progression from differential block
A alpha
A beta
A gamma
A delta
C fibers
B fibers
Sympathetic level is ….
2-6 levels higher than sensory level - B fibers
sensory level is…..
2 levels higher than motor block
which block is segmental?
epidural
Elimination of LA from SAB…
all LAs are eliminated by reuptake
vasular reabsorption
What drugs have a high affinity for epidural fat?
lipophilic drugs = slow reuptake because of the fat affinity
Most important factors affecting LA distribution and block height for spinal
Dose
Baracity
CSF volume
Advanced age
pregnancy
Pt position
Epidural injection post spinal (EVE- epidural volume extension)
Water specific gravity
1.000
CSF specific gravity
1.00033 (pregnant)
1.00067 (men)
what is the most reliable determinant of LA spread for spinal
dose
what LA are primarily influenced by baracity
hyperbaric LA
How to make hypobaric solution
water 3x vol SAB LA
baracity for upper abd surgeries
hyperbaric
c-section
Baracity for hemerrhoidectomy
hypobaric
pt is prone
Dose of hyperbaric SAB in nonOB for T4
2ml
Dose of hyperbaric SAB in nonOB for T10
1.5 ml
Dose of hyperbaric SAB in nonOB for Sacral level
1 mL
swirl is present in….
hyperbaric solution
ED 50 for bupivacaine
4.7 mg - 9.8 mg
ED 95 for bupivacaine
8-15 mg
balanced anesthesia
muscle relaxation
analgesia
amnesia
hemodynamic stability
CSF volume
100-160 ml
small CSF volume correlates with….
extensive spread of LA in intrathecal space= more effect
Bain bridge reflex
reflex thats mediated via sensors from the ns that feedback onto the nodal tissue through reductions in vagal tone
Involves some sensory neurons and when they see increase stretch they feed back to the vagal nerves and tell the vagal nerves to slow firing = increase hr.
Amount of hr increasing- full initiation of the bainbridge reflex by itself with nothing else = increase hr by 50%.
LA on the heart
inhibition of bainbridge reflex,
block T1-T4
Bezold Jarisch reflex
block T1-L3/4 (SNS output)
The Bezold-Jarisch reflex
Seratonin -> chemo and mechano receptors on LV -> inc parasympathetic, decreased sympathetic output
zofran on hypotension
inhibits Bezold-Jarisch reflex
Fluids to give for preloading/coloading
isotonic; NS, LR, Osmolyte A
GI sympathetic outflow originates
T6-L1
what respiratory capacity changes with SAB
vital capacity decreases because of loss of abd muscle contribution to forced expiration
What sympathetic blockade affects bladder control
T10
urinary sphincter tone relaxed
Why is there shivering with SAB
Blockade impairs central thermoregulation center of the brain
vasodilation -> redistribution of blood flow and heat to periphery
Prevention of shivering
ondansetron
bare hugger
High thoracic blockade can result in the blockade of respiratory ….
accessory muscle (intercostal and abdominal muslces)
Ester metabolite
paba =allergies
3 common reasons for neuraxial failure
wrong dose, wrong location, wrong position
Saddle block
S2 -S5
Interlipid dose
20%; 1.5 ml/kg (bolus)
gtt 0.25ml/kg
C section dermatome level
T4
quincke type of spinal needle
cutting
sprotte type of spinal needle
non cutting
Whitacre type of spinal needle
non cutting
Another name for non cutting needles
pencil-point
Lateral position is good for neuraxial procedures for what surgeries?
Hip surgeries (can use hypobaric solution)
Benefit of non-cutting spinal needle
feel more of pop when through Dura
reduced incidence of post-dural puncture HA
Layers transverse during median approach
skin
subq fat
supraspinous ligament
interspinous ligament
ligamentum flavum
dura mater
subdural space
arachnoid mater
subarachnoid space
Layers transversed during paramedian approach
skin
subq fat
ligamentum flavum
dura mater
subdural space
arachnoid mater
subarachnoid space
succinylcholine brand name
anectine
bupivicaine brand name
marcaine
needle hits bone early in spinal
hitting spinous process
point the needle caudad
needle hits bone late in spinal
hitting lamina
point the needle cephalad
spinal anesthesia needle size
25 guage
epidural needle size
18-19 guarge
Low csf from post-dural puncture headache leads to
cranial nerve traction
traction causes
diplopia (CN VI)
tinnitus (CNVIII)
Name for end of the spinal cord
conus medularis
what relieves PDPHA
supine
nsaids and narcotics (fent)
(caffeine)
blood patch
amount of blood used for blood patch
20 mL
transient neurologic symtoms
develops immediately
resolves within a week in 90% of cases
11.9% incidence rate (5% lido)
severe radicular back pain
positional correlation (hip or knee flexion) -> stretched spinal roots
cauda equina sydrome
permanant-> can lead to paraplegia
pooling of lido (5%) in cauda equina = dense blockade
Cauda equina sydrome s/s
bowel/bladder dysfucntion
paraplegia (late sign)
back pain
saddle anesthesia
sexual dysfunction
cauda equina location
L1 -S4 + coccygeal nerves
causa equina sydrome treatment
if compression is a factor, then immediate laminectomy > 6hrs
horners syndrome
ptosis
anyhydrosis
miosis
high sympathetic spred
trigeminal nerve branches
CN5
V1 = opthalmic
V2 = Maxillary
V3 = Mandibular
Trigeminal nerve palsy
ganglion bathed in CSF
Nerves to block for awake intubation
Glosspharyngeal - 9- suck on tongue depressor and 4x4
Vagus - 10-
Trigeminal nerve - 5 (V2) - cotton q tip in nose
Vagus nerve branches
recurrent layrngeal nerve
superior laryngeal branch - internal and external branches
Superior laryngeal nerve
internal = sensory innervation for larynx
external = motor function for cricothyroid muscle
Inflammation of meninges
Arachnoiditis
Leads to extensive sclerosis of arachnoid membranes and constriction of vascular supply
Symptom of numbness/weakness confusing by the use of local anesthetics; Pain is a major symptom
Epidural/Spinal Hematoma
Cord ischemia reversible if laminectomy is performed in < 8 hours
Can maintain the ability to ambulate and void if epidural is placed
above T10
Epidural space extends…
Extends from the base of the skull to the sacral hiatus
Epidural space is filled with….
filled with the fat, areolar tissue, lymphatics, veins, nerve roots and blood vessels
onset of LA is based on….
closer PKA is to physiologic Ph = faster onset
exception to the rule = 2-chloroprocaine 3%
Uptake of LA based on regional anesthetic technique
IV
Tracheal
Intercostal
Caudal
Paracervical
Epidural
Brachial
Sciatic
SubQ
Epidural injection diffuses…
diffuses through the dural sheath of spinal nerves, roots, rootlets, and CSF where nerve transmission is altered
Determinants of block spread for epidural
Volume and dose of LA
increased epidural pressure can _______ spread in epidurals
increase spread
pregnancy, coughing,Valsalva, obesity
Lumbar epidural injection produces a preferential ______spread
cephalad
due to the narrowing of the epidural space at the lumbosacral junction
The larger diameter of the L5-S1 nerve roots may delay the onset or result in patchy anesthesia.
Thoracic epidural injection produces _____ spread of anesthetic solution
symmetrical
A reduced volume of local anesthetic solution should be used at this level because of the potential for higher block and resultant hemodynamic instability
Caudal injection predominantly results in…..
sacral and low lumbar anesthesia
what determines epidural dermatome spread?
volume
A larger volume will block a greater number of segments
incremental dosage = _______
5 mL at a time
Epinephrine increases the ________ of useful epidural anesthesia with all the agents
duration
Greatest with lidocaine, mepivacaine, and 2-chloroprocaine
Dose of bicarb and what it does to the LA
Alkalinization - Adding NaHCO3 (1 mEq/10 mL of local anesthetic)
Increases the pH of LA
Increase the concentration of nonionized free base
2- chloroprocaine can only be used in….
epidural
metabolized by plasma cholinesterase
medication with greatest motor function depression for epidural
Lidocaine
ropivacaine is the least
Fastest to slowest onset and shortest to longest duration
2 - chloroprocaine 3%
lidocaine 2%
mepivacaine 2%
ropivicaine 0.7%
bupivacaine 0.5%
Test dose dose
3 ml of lidocaine 1.5% with epidural (1:200,000)
Epidural needle with the most curvature (30 degrees) blunt tip is less likely to puncture subarachnoid space
Tuohy
Epidural needle with 15 degree curve
Hustead
Medication that decreases efficacy of subsequent epidural opioids?
2 chloroprocaine
Epidural needle preferred when catheter placement is difficult or the angel is steep (thoracic epidural)
Crawford
Epidural needle markings
Each mark = 1 cm
9 cm length - hub
10 cm - window
12.5 cm = hub
Epidural cath placed _____ within the epidural space
placed 3-5 cm
Epidural catheter markings
thicker marking = 11 cm
small marking = 5 cm increments
Distance from Skin to Epidural Space
Average adult is 4-6 cm (80% of patients)
Reason for test dose
Identify unintentional IV or SAB
A change of ______ or greater in heart rate after the test dose indicates a probable intravascular injection
20%
S/S of IV injection of LA = Positive test dose
Tinnitus
Metallic taste
Circumoral numbness
The intrathecal injection of lidocaine will produce a significant______ block consistent with_______ anesthesia in _____ mins
The intrathecal injection of lidocaine will produce a significant motor block consistent with spinal anesthesia in 3 mins
A dense motor block within 5 min of a test dose should prompt a suspicion of a spinal block
Spinal nerves in subarachnoid space is covered by thin…..
pia layer
Saddle block
S2 -S5
Spinal hematoma treatment
cord ischemia is reversible if laminectomy is performed in 8 hrs.
Major symptom of spinal hematoma
pain
res ipsa loquitur
the principle that the occurrence of an accident implies negligence.
