Apex- Neuraxials Flashcards
What are the others?
A- Transverse process
B- Superior articular process
C- Lamina
D- Spinous Process
How many vertebrae in the spine?
_ cervical, _ thoracic, _ lumbar, _ fused-sacral, _ fsed-coccygeal
33
7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, 4 fused coccygeal
The spinal nerves exit the vertebral column through what?
the intervertebral foramina
What do the facet joints do?
what can injury to a facet joint do?
they guide and restrict movement of the vertebral column
it can compress the spinal nerve as it exits the respective intervertebral foramina, causing pain and muscle spasm along the associated ermatome
Purpose of the intervertebral discs?
what happens when they degenerage?
they act as a shock absorber
the size of the intervertebral foramina reduces and can cause nerve compresion
What is the space that contains the spinal cord, nerve roots and epidural space?
vertebral foramen
label
C1 vs C2 - which one is the atlas and which one is the axis
C1- atlas
C2 - axis
atlas spins on the axis
whats the zygapophyseal joint?
the facet joint
formed by the inferior articular process of the above vertebra and the superior articular process below
What is the name (2) of the horizontal line drawn across the superior aspects of the iliaccrests and what vertebra does it correlate with?
intercristal line (Tuffier’s line)
L4
space above = L3-L4, space below = L4-5
Infants up to 1 year, the intercristal ilne correlates with what interspace?
L5-S1
What vertebral level corresponds with the spine of scapula?
What about the inferior angle of the scapula?
T3
T7
What vertebral level corresponds with the posterior superior iliac spine
What about the superior aspect of the iliac crest?
S2
L4 (intercristial line)
What vetebral level corresponds with the vertebra prominens?
C7
What vertebrae corresponds with the rib margin 10cm from midline?
L1
In the adult, which anatomic structure correlates with the termination of the dural sac?
A. Sacral cornua
B. Superior iliac spines
C. Tuffier’s line
D. L1 vertebra
B. Superior iliac spines
Superior aspects of the iliac CREST vs
Posterior suprior iliac SPINE
veretebre correlation vs landmark associate
iliac CREST : L4-5 interspace (Tuffier’s line)
iliac SPINE: S2 (Dural sac ends)
What vertebra is is the conus medullaris associated with?
L1
What provides an entry point to the epidural space that’s useful in pediatrics?
what vertebra does it coincide with? What is it covered by?
What’s the landmark for caudal anesthesia?
Sacral hiatus = entry point into the epidural space
S5 ; covered by the sacrococcygeal ligament
Sacral Cornua = landmark
The Spinal cord ends in a taper as the what?
Infant vs Adult
Conus medullaris
Adult - L1-L2
Infant: L3
What is the cauda equina?
what nerve and nerve roots is it made up of?
A bundle of spinal nerves extending from the conus medullaris to the dural sac
L2-S5 nerve and nerve roots & the coccygeal nerve
Where does the subarachnoid space end?
Landmark for adult vs infant?
dural sac
adult - S2
Infant - S3
What are the 5 ligaments of the spinal cord from superficial to deep?
which ones do you pass through with the midline approach to a spinal?
which ones what about the paramedian approach?
- supraspinous
- interspinous
- ligamentum flavum
- posterior longitudinal
- anterior longitudinal
supraspinous, interspinous, ligamentum flavum
paramedian = just the ligamentum flavum
What contributes to the loss of resistance encountered during neuraxial anesthesia?
piercing the ligamentum flavum when the needle enters the epidural space
2 ways t odo a paramedian approach?
15 degrees off midline or
1cm lateral and 1cm interior to the interspace
Where does the epidural space end?
The sacrococcygeal ligament
What 3 things does the epidural space contain?
What 4 things does the subarachnoid space contain?
nerve roots, fat pads, blood vessels
Spinal cord, CSF, nerve roots & rootlets
Significance of fat pads in the epidural space?
they act as a sink for lipophilic drugs, reducing their bioavailability
What will happen if an epidural dose vs spinal dose is injected into the subdural space
epidural dose will cause a high spinal
spinal dose will cause a failed spinal
What are Batson’s plexus?
Epidural veins that drain venous blood from the spinal cord
What’s the thing that may or may not exist but people blame as a culprit for difficult epidural catheter insertion or unilateral epidural blocks?
plica mediana dorsalis
-a connective band of tissue b/t the ligamentum flavum and the dura matter that could create a barrier and would impact the spread of medications within the epidural space
What structures does the needle pass through after piercing the ligamentum flavum?
epidural space > dura mater > subdural space > arachnoid mater > subarachnoid space > pia mater > spinal cord > posterior longitudinal ligament> bone
when performing spinal anesthesia, when do you feel the “pop”
once you pass through the dura mater (fibrous sheild that protects the spinal cord)
Transection of the C6 posterior nerve root will cause:
A. Diaphragmatic paralysis
B. Impaired sympathetic outflow to the C6 distribution
C. Sensory block of the thumb
D. Motor deficit of the middle finger
Sensory block of the thumb
*posterior roots = sensory; anterior roots = motor & autonomic
Diaphragmaticp aralysis would be injury to C3-C5
The spinal cord has how many paired spinal nerves?
31
what is a dermatome
an area of skin thats innervated by a dorsal nerve root (sensory) from the spinal cord
Dermatomes for:
C6, C7, C8
C6 = thumb
C7 = 2nd and 3rd digits
C8 = 4th and 5th digits
Dermatome levels for:
Nipple line, xiphoid process, umbilicus
anterior knee
Nipple line = T4
Xiphoid process = T6
Umbilicius = T10
L4 = anterior knee
label
label
With spinal anesthesia, what is the primary site the local anesthetic works on?
the myelinated preganglionic fivers of the spinal nerve roots
spinal anesthesia- which fibers/nerves are blocked first, second, third between motor, autonomic and sensory
first- autonomic (sympathectomy)
second- sensory
third- motor
(this is why that one CRNA only asks if they can lift their legs, bc if motor is blocked, than you know sensory is blocked, esp if you have a sympathectomy
Spinal anesthesia- autonomic block is how many dermatomes higher than the sensory blockade, and how much higher than the motor blockade?
compared to epidural?
autonomic 2-6 higher than sensory block
sesnory block = 2 dermatomes higher than motor
sensory block is 2-4 dermatomes higher than the motor block and there is no autonimic differential blockade
T/F- there is no autonomic differential blockade with epidural anesthesia
True
Where must local anesthetics go before blocking the nerve roots when injected epidurally?
they have to diffuse through the dural cuff before they can block the nerve roots
Primary determinants of spreaad for spinal vs epidural anesthesia (4/2)
spinal = dose and baricity; pt position and injection site
epidural = volume and level of injuection
t/f: bevel orientation does NOT meaningfully affect spread of the local anesthetic in the spinal space
true
what is the most reliable determinant of intrathecal spread when using a hypo or isobaric solution compared to a hyperbaric solution
hypo or isobaric -> dose = most reliable determinant of spread
hyperbaric > baricity = most reliable determinant of spread
*spinal = dose and baricity (position and site of injection)
Order of sensations blocked from first to last
1st = temp (alch pad)
2nd = pain (pinprick)
3d = light touch or pressure
Ratings of the modified bromage scale to assess the degree of motor block
0 = no motor block
1 = cant raise leg but can move knees and feet
2 = cant raise leg or move knee but can move feet
3 = complete motor block (cant move legs, knees, or feet)
What is the MOST appropriate spinal dose of 3% 2-chloroprocaine to achieve for a T10 level?
A. 5mg
B. 20mg
C. 30mg
D. 50mg
C. 30mg
3% 2-cholorprocaine is useful for pts who require a spinal for a very short period of time. The range needed to achieve a T10 level is 30-40mg.
What is the primary DRUG-related determinant of block height for an epidural?
what about primary PROCEDURE-related determinant?
what about primary determinant of block density?
drug-related factor = LA volume
PROCEDURE-related factor = level of injection
primary determinant of block density = LA concentration
0.5-0.75% BPV (no dextrose)
Dose for T10 vs T4
onset
duration
T10 - 10-15mg (2-3cc 0.5%; 1.3-2cc 0.75%)
T4 - 15-20mg (3-4cc 0.5%; 2-2.6cc 0.75%)
onset 4-8 mins
duration 130-220 mins (2-3.5hrs)
How much volume of epidural LA per segment to be blocked
what if your inserting epidural at L4-5 and want a T4 height?
1-2cc
(12 segments: 12-24ccs)
What is the “top-up” dose for epidurals?
50-75% of initial dose
What’s a “walking epidural”
when you use low enough concentration that provides analgesia but preserves motor function.
For a spinal, how many mL of 0.75% bupi are required to produce a T10 block?
0.75% BPV = 7.5mg/ml
T10 dose = 10-15mg
Volume = 1.25-2mls
For a spinal, how many mL of 3% 2-chloroprocaine are required to produce a T4 block?
3% 2-choloroprocaine = 30mg/ml
T4 dose = 40-60mg
Volume = 1.33-2mL
Idenitfy the MOST appropriate techniques for a subarachnoid block in a patient scheduled for a hemorrhoidectomy (select 2):
-Lidocaine 5% in 7.5% dextrose in the sitting position
-BPV 0.3% in water in the jackknife position
-Tetracaine 0.2% in water and the sitting position
-Procaine 10% in water and the jacknife position
-Lidocaine 5% in 7.5% dextrose in the sitting position (hyperbaric-sink)
-BPV 0.3% in water in the jackknife position (hypobaric-float)
-hypobaric in a sitting positon (tetra with water) would make the LA rise, failing to anesthetize the sacral nerve roots
-hyperbaric (procaine 10% + water) in jackknife (head down) - it will still rise towards the head (it sinks and gravity will take it towards the head), failing to anesthetize the sacral nerve roots adequately
Why is baracity a factor with spinal anesthesia but not epidural?
bc baracity has to do with the density of the local anesthetsic relative to the CSF (spinal space)
Hyperbaric, hypobaric, isobaric
hyperbaric sinks
hypObaric flOats
isobaric stays
isobaric, hypobaric, hyperbaric - what solutions make each
what is procaine 10% in water considered?
iso- saline
hyper = dextrose
hypo= water
hyperbaric bc 10% solution contains a lot more molecules
What is density?
density varies directly/inversly with temp
mass/volume
-the mass of a substance relative to it’s volume
density varies INVERSELY with temp (hot water expands, density reduces; cold water contracts, density increases)
What is specific gravity?
the density of a substance relative to the density of another substance (usually water)
baricity compares LA density to CSF at 37 degrees)
specific gravity of CSF
baricity?
1.002-1.009
baricity = 1
what would happen if the patient remained sitting after a spinal injection with a hyperbaric solution?
what happens when you lay them supine?
it would sink and anesthetize the sacral nerve roots (saddle block)
when you lay the ptaient supine, the hyperbaric solution will slide down the lumbar lordosis and pool in the sacrum and thoracic kyphosis
What would happen if you injected a hypobaric solution and kept the patient sitting?
what if you lay them supine?
sitting- it would rise towards the brain (not a good idea)
supine, it would float towards the lower lumbar region; it doesnt float towards the cervical region bc it would need to sink into the thoracic kyphosis first- which it wont
What would happen if you injected a hypobaric solution and kept the patient sitting?
what if you lay them supine?
sitting- it would rise towards the brain (not a good idea)
supine, it would float towards the lower lumbar region; it doesnt float towards the cervical region bc it would need to sink into the thoracic kyphosis first- which it wont
What are the 2 highest points of lordosis in the supine position?
C5 & L3
What are the highest points of kyphosis in the supine position?
T5-T7 & S2
If someone goes apenic on you after a spinal, what is most likely the cause?
brainstem hypoperfusion (decreased blood flow to the ventilatory centers in the medulla)
NOT phrenic nerve paralysis or high spinals
why can spinals make someone drowsy?
bc it reduces sensory input to the reticular activating system which causes drowsiness
how does spinal anesthesia affect the gut?
sympathectomy - increased parasympathetic tone to the gut, sphincters relax and peristalsis increases
how are the kidneys and liver affected by spinal anesthesia?
they arent as long as the BP is maintained
How do neuraxial opioids block pain?
they inhibit afferent pain transmission in the substansia gelatinosa (rexed lamina 2 in the dorsal horn)
decreases cAMP > reduced CA+ conductance + increased K+ conductance
why use neuraxial opioids in addition to the local anesthetic?
creates a denser block
t/f- neuraxial opioids also diffuse into systemic ciurclation
true - blood delivers them to the opioid receptors throughout the body
Most common side effect of neuraxial opioid administration
what are the other 3
pruritus
resp depression, urinary retention, n/v
what may re-activate herpes simplex labialis type 1 (ie cold sores) in OB and postpartum patients?
epidural morphine
do opioids injected into the epdiural space transfer to breast milk?
minimally
why is increased ICP a relative contraindiation to spinal anesthesia?
the sudden change in CSF pressure increases the chance of brain herniation
spinal or epidurals are okay as long as the platelet count is what
100,000
why shouldn’t you do a spinal in a septic patient?
contaminated blood can be intoduced into the BBB and worsening hypotension
Which 2 spinal needles have a cutting tip
what are the 4 non-cutting tips? pencil vs rounded?
quinke & pitkin
pencil = sprotte, whitacre, pencan ; rounded = greene
label the epidural needles
touhy = 30 degrees
husted = 15 degrees
crawford = 0
*goes in alphabetical order with needle angle
In the lumbar region of most adults, the epidural space is how many cm from the skin?
what is the optimal depth of catheter insertion inside the epidural space?
3-5cm from skin
3-5cm (so 6-10cm from skin)
how do you figure out how far to insert your epidural catheter?
after you enter the epidural space, look on the needle how far you are in and minus it from the total lenght of the needle (usually 9cm)
> ex if your at the 4cm mark, 9-4 = 5cm
> so 5cm into the epidural space + you want the catheter 3-5cm into the epidural space , so 8-10cm
What might happen if you insert the epidural catheter too far? (2 things)
it could enter a epdiural vein or exit through an intervertebral foramen
A 22# child requires a caudal anesthetic. how many mls of 0.2% ropivacaine should be administered to achieve a T10 sensory blockade?
For a T10 sensory block = 1ml/kg
first convert # to kg: 22/2.2 = 10kg
10kg x 1 ml = 10mls
3 absolute contraindications to caudal anesthesia
- spina bifida
- meningomyelocele of the sacrum
- meninigitis
T/F- you should always use air for loss of reistance in children
false - never - risk of air emboli
what determines the height of a caudal block?
volume (like an epidural)
landmarks for caudal anesthesia
posterior superior iliac spines and the sacral hiatus
T/F- a feeling of fullness in the sacrum before a caudal block sets is a normal response
True
why should you select a lower concentration of LA for cadudals
bc the goal is isually analgesia- not surgical anesthesia (as these pts are usually put to sleep)
What ligament is punctured when performing a caudal anesthetic?
sacrococcygeal
T/F- risk of epidural hematoma is greater during block placement than catheter removal
false- risk is similar
Epidural hematoma symptoms (4)
treatment?
lower extremity weakness, numbness, low back pain, bowel and bladder dysfunction
surgical decompression within 8 hours
How long do COX-1 inhibitors need to be held prior to neuraxial anesthesia?
examples
none as long as overall coagulation status appears normal
NSAIDS & Asprin
When can thienopyridine derivatives be resumed after epidural cath removed?
what about glycoprotein IIb/IIIa antagonists (abciximab, tirofiban)
24 hours
4 weeks
how ong should clopidogrel be held before block placement?
5-7 days
resume 24 hours after cath out
how long should heparin be held prior to bock placement: low dose (5,000u TID, higher dose up to 20,000u/day, therpautic dose > 20,000u/day)
when can heparin be resumed after block placement?
what about after cath removal?
low = hold 4-6 hrs
mod = hold 12 hours
high = hold 24hrs
restart 1 hr after placement
restart 1 hr after removal
how long should u wait to pull epidural cath if pt received SC/IV heparin
4-6 hours
how long to wait before placing epidural if on LMWH prophylactic vs theapeutic dosing
when can dosing be resumed after block placement
what about after catheter removal?
prophylactic - delay 12 hrs
therapeutic- delay 24 hrs
12hrs
4 hours (24hrs if blood in needle or catheter)
How long should warfarin be held prior to block placement?
at what INR can you remove it?
5 days; verify normal INR
wait until INR < 1.5 to remove
How should you proceed if you see your patient takes garlic, ginko, or ginseng?
proceed as long as they arent on any other blood thinning agents
*these drugs inhibit platelet aggregation
Explain the pathophys of post-dural puncture headaches
puncturing the dura causes CSF to leak from subarachnoid space
→pressure is lost, cerebral vessels dilate to compensate (h/a)
→ also, the brainstem sags into the foramen magnum, stretching the menineges and pulling on the tentorium (h/a)
characteristics of a post-dural puncture headache
what 5 things may it be accompanied by?
what position makes it worse vs beter?
fronto-occipital headache
n/v, photophobia, diplopia, tinnitus
upright → gravity → worse; supine = relief
how can you determine if it’s a postdural puncture headache? what can you have the patient do?
sit upright, lay down; sitting up will make it worse, supine will make it better
3 patient risk factors for PDPH
young, female, pregnant
4 practitioner risk factors for PDPH
- cutting needle
- larger diameter needle
- using air for LOR with epidural
- needle perpendicular to the long-axis of the neuraxis
5 treatments for PDPH
- bed rest
- nsaids
- caffine (cerebral vasoconstriction)
- epidural blood patch (definitive tx)
- sphenopalantine ganglion block
definitive tx for PDPH that has a 90% success rate
epidural blood patch
how to do a epidural blood patch
when do you know to stop?
10-20ml venous blood is drawn from patient
then it is re-introduce into the epidural space
stop when pt senses pressure in her legs/butt/or back
2 reasons why an epidural blood patch works?
- it increases CSF pressure by compressing the epidural and subarachnoid spaces
- acts as a plug to prevent further leaks
what kind of block can be done for a PDPH
how is it done?
sphenopalantine ganglion block
- soak a long cotton tipped-applicator in a local anesthetic solution (1-2% lido or 0.5% BPV)
- put pt in sniffing position
- insert the applicator into each nare towards the middle turbinate
- continue inserting until you encounter the posterior all of the nasopharynx (where the sphenopalantine ganlion is)
- leave applicator in place for 5-10 mins
3.
- leave applicator in place for 5-10 mins
2 ways an infectious organism can reach the CSF during neuraxial block
- failure of sterile technique
- bacteria in the patient’s blood at time of SAB
what is one of the most common culprits for post-spinal bacterial meningitis
where is it most commonly found?
Steptococcus viridans
commonly found in the mouth (wear a mask); and on the hands and forearms
what do you need to think about if your using chlorhexidine to prep for a spinal?
it’s neurotoxic (risk of arachnoiditis) - must be allowed to dry
what does miller say is the most effective prpearation method to prevent post-spinal bacterial meningitis?
a combo of alcohol and chlorhexidine
what are the 2 most common side effects of an epidural blood patch?
back pain and radicular pain
*Radicular pain occurs when the spinal nerve gets compressed (pinched) or inflamed.
Following the resolution of a spinal, the patient complains of severe pain in the buttocks that radiates through her legs. She has normal motor function. What should be said to the patient?
what is the patient experiencing?
Take NSAIDS
Transient neurologic symptomcs
How long do transient neurologic symptoms typically persist for?
what LA is the most common cause of it?
1-7 days
Lidocaine
T/F- spinal microcatheters increase the risk of transiet neurologic symptoms
False - cauda equina syndrome
What causes cauda equina syndrome?
what 2 things increase the risk?
neurotoxicity from high concentrations of local anesthetic
5% lidocaine and spinal microcatheters (delivering a high concentration in a very small area)
S/S of TNS vs Cauda equina
tx?
TNS - severe back/butt pain that radiates to both legs
Caudua equina - bowel and bladder dysfunction, snesory deficitys, weakness/paralysis
TNS- NSAIDS, opioids, trigger point injections
CE - supportive
Other than 5% lido and spinal microcatheters, what are 3 other things that increase the risk of TNS?
lithotomy, ambulatory surgery, and knee arthorscopy
3 things that increase the risk of spinal-induced hypotension
block higher than T5 level
older than 40yo
opening BP < 120
How does Odansetron help prevent spinal-induced hypotension?
bc it’s a 5-HT3 ANTAGONIST and the bezold-jarish reflex is thought to be mediated by 5-HT3 receptors in the vagus nerve and ventricular myocardium
Should we give a fluid bolus before performing a spinal?
no longer recommended- minimal effect
*“Co-loading” (rapid administration of IVF just after performing the block) 15ml/kg is more effective (open your fluids before getting dressed)
2 reasons you wouldnt want to put the pt in trendelenberg to treat spinal-induced hypotension
- can increase height of spinal if not set yet
- reduce venous drainage from the head, impairing cerebral perfusion
What does blood return in an epidural needle or catheter suggest?
placement in an epidural vein
T/F- if a spinal does not set up after 15-20 minutes, it’s reasonable to repoeat the injection
true
What can you do if the patient ends up with a unilateral block?
position them with the unblocked side down and administer several mL of local anesthetic (umm what?)
if that doesnt work (whic hwho is doing this anyway) you can supplement with IV sedation or GA
How should you pull back an epidural catheter with a needle inside?
both need to be pulled back simultaneously
withdrawing the catheter through the needle can cause the catheter to sheer, which might leave fragments inside the patient
What should you do if you iencounter resistance when you try to remove the epidural catheter?
have patient assume orginal insertion position or lateral decub
& apply gentle, continuous traction
what should you do if you get blood in the epidural needle vs epidural catheter?
if it’s in the needle, it was likely inserted too laterally → redirect midline
if it’s in the catheter, pull back a little and flush it with saline and repeat until your unable to aspirate blood
what is the most common cause of a unilateral epidural block?
the catheter was inserted too far and the tip exited the epidura lspace through an intervertebral foramen
try pulling back 1-2cm, position lateral decub, adiminister several mL of a dilute concentration of LA
An 8kg pediatric patient is scheduled for circumcision under GA with a caudal block. What is the MOSt appropriate local anesthetic to administer for the block?
A. 2mL of 0.5% BPV
B. 4mL of 0.25% ropi
C. 8ml of 0.25% BPV
D. 1ml of 0.5% ropi
B. 4mL of 0.25% ropi
to block sacral nerve rooots, common appraoch is to give 0.5ML/kg of a lower concetration of a local anesthetic (goal is analgesia- not surgical anesthesia)
