Neuraxial Flashcards
What is density?
The ratio of mass to volume
What is specific gravity?
The density of a substance relative to another substance (usually the density of something compared to the density of water)
What is baricity?
The specific gravity where CSF is the substance being compared to (rather than water)
What is added to increase baricity?
Dextrose
What is added to decrease baricity?
Water
What are the highest points of lordosis in the supine position?
C5 and L3
What are the highest points of kyphosis in the supine position?
T6 and S2
In the supine position, how will an an intrathecal hypobaric solution spread?
In the lower lumbar region, because in order to reach the cervical region it would have to sink to the thoracic lordosis, which it can’t do
What is the primary mechanism of hypotension with neuraxial anesthesia?
Blockade of sympathetic preganglionic B fibers (sympathectomy)
The spine of the scapula corresponds with what vertebral level?
T3
The tip of the scapula corresponds with what vertebral level?
T7
What is the intercristal line?
Tuffier’s Line
In infants up to 1 yr, Tuffier’s line corresponds with:
L5-S1
The spinal cord ends in a taper called _______ at _________
conus medullaris
L1 (L3 in infants)
Where does the dural sac end?
S2 in adults
S3 in infants
What is the Filum Terminale?
A continuation of the pia mater below the level of the conus medullaris. It helps anchor the spine to the coccyx
Which veins drain the spinal cord and meninges?
Batson’s Plexus, which passes through the lateral and anterior regions of the epidural space
The epidural space contains:
nerves
fat pads
blood vessels
Name the dermatomes:
C6
C7
C8
T4
T6
T10
L4
Posterior nerve roots carry:
Sensory information
Anterior nerve roots carry:
motor and autonomic information
With spinal anesthesia, how much higher is autonomic blockade than sensory blockade?
Autonomic blockade is 2-6 dermatomes higher than sensory blockade
With spinal anesthesia, how much higher is sensory blockade than motor blockade?
Sensory blockade is two dermatomes higher than motor blockade
In the lumbar region, spread is primarily ________
cephalad
LA spread In the midthoracic region is _________
equally cephalad and caudad
In the cervical region, spread is mostly ______
caudad
With epidural anesthesia, how much higher than sensory blockade is autonomic blockade?
There is no differential autonomic blockade with epidural anesthesia! Only spinal! BUT motor blockade 2-4 dermatomes lower
Which sensory modality will fade first?
Temperature
Then Sharp
Then pressure
The primary drug-related determinant of epidural block HEIGHT is:
Volume
The primary drug-related determinant of epidural block DENSITY is:
LA concentration
How does neuraxial anesthesia impact respiratory mechanics?
It impairs inspiration and expiration because it knocks out accessory muscles
Does spinal anesthesia cause drowsiness?
Actually yes. It reduces sensory input to the RAS
How does spinal anesthesia impact the gut?
Increases peristalsis and relaxes sphincters
What reflex contributes to asystole from spinal anesthesia?
Bezold-Jarisch: the heart slows to allow time to fill
What is the most likely cause of apnea with spinal anesthesia?
Brainstem hypoperfusion
Neuraxial opioids do NOT impact:
sympathectomy
proprioception
motor blockade
What is the MOST lipophilic opioid?
Sufentanil
What is the LEAST lipophilic opioid?
Morphine
How will a lipophilic opioid behave in the subarachnoid space?
Shorter duration
Less spread
Early resp depression
How will a hydrophilic opioid behave in the subarachnoid space?
Longer duration
Wider Spread
Late resp depression
How do neuraxial opioids inhibit pain?
They inhibit afferent pain transmission in the substantia gelatinosa
How do neuraxial opioids impact block density?
They increase density when combined with LAs
Which LA decreases the efficacy of neuraxial opioids?
2-chloroprocaine
Early phase respiratory depression results from:
systemic absorption
Late phase respiratory depression results from:
rostral spread of LAs to the brainstem
Late phase respiratory depression is only caused by ______ opioids
hydrophilic
Urinary retention is most common in which demographic?
young men
N/V from neuraxial opioids results from stimulation of ________
area postrema of the medulla
vestibular apparatus
Which opioid may reactivate herpes simplex labialis type 1?
Morphine can reactivate oral herpes 2-5 days after administration
Sedation from neuraxial opioids is most common with which drug?
Sufentanil
How do opioids impact diuresis?
They have an antidiuretic effect by increasing vasopressin release
Describe the degree of transfer between epidural opioids and breast milk
Negligible
Is increased ICP a contraindication to spinal anesthesia?
Yes. Any sudden change in CSF volume can cause herniation
What three cardiac abnormalities should not be candidates for spinal anesthesia?
Ao and Mitral stenosis
hypertrophic cardiomyopathy
Can MS patient receive spinal anesthesia?
Yes. There is a small chance of exacerbation.
You should use a lower dose and concentration of LA because myelination is disturbed
In the lumbar region, the epidural space is _______ cm from the skin
3-5
Caudal anesthesia is useful in procedures requiring a ______ level block
T10 or lower
What are absolute contraindications to caudal anesthesia?
Spina Bifida
Meningomyelocele
Meningitis
How should LOR be assessed in caudal anesthesia?
It should always be with saline, NEVER air
How should a patient be positioned for a caudal anesthetic?
Either in Simm’s Position OR Prone
In a patient receiving lovenox, how should the medication be timed to remove the epidural?
Hold lovenox for 12 hours, pull the epidural, then restart four hours later
Is aspirin a contraindication for neuraxial anesthesia?
No
How long should plavix be held before neuraxial?
7 days?
How long should lovenox be held for neuraxial?
12 hrs for prophy
24 hrs for therapeutic
Which organism is usually responsible for post-spinal bacterial meningitis?
Streptococcus Viridians
How is a sphenopalatine block performed?
What factors increase the risk of transient neurological symptoms?
Lidocaine
Lithotomy
Knee Arthroscopy
What are the s/s of TNS?
Severe back and butt pain that radiates to both legs
How long does TNS last?
1-7 days
What helps with TNS symptoms?
NSAIDs
Opioids
Trigger point injections
What should you do if an epidural catheter segment breaks off during removal?
What should you do in the event of a patchy spinal?
Don’t repeat the spinal, since the risk of neurotoxicity is high. Transition to another technique.
What should you do in the event of a completely failed spinal?
Repeat in 15-20 minutes
What should you do in the event of unilateral spinal?
Position poorly blocked side down
Give a few mL of local IV
If that doesn’t work. convert
What is the most common cause of a unilateral epidural?
Catheter in too far
Should you pull back on an epidural catheter with the needle in face?
No. You have to remove both simultaneously
Which spinal nerves are the most resistant to LAs?
L5 and S1
They are the thickest
