Neuraxial (Epidural, Spinal) Anesthesia Flashcards
Vertebra prominens landmark
C7
Spine of Scapula landmark
T3
Inferior angle of scapula
T7
Rib margin 10 cm from midline
L1
Superior aspect of iliac crest
L4
Posterior superior iliac spine
S2
Horizontal line drawn across the superior aspects of the iliac crests that correlate with L4
Intercristal line (Tuffier’s line)
the interspace ABOVE the intercristal line correlates with…
L3-L4
The interspace BELOW the intercristal line correlates with….
L4-L5
Infants up to 1 year, intercristal line correlates with…
L5-S1
Conus medullaris
L1
Dural sac ends at….
S2 (correlates with superior iliac spines)
Sacral hiatus and sacrococcygeal ligament landmark
S5
Provides and entry point to the epidural space useful in peds
sacral hiatus
Used as landmarks for caudal anesthesia
Sacral cornua
Conus medullar is in adults? Peds?
Adults= L1-L2
Peds= L3
Cauda equina extends from ______ to the ________.
from conus medullaris to the dural sac
The subarachnoid space terminates at the ________.
Dural Sac (Adult= S2, Peds= S3)
Anchors the spinal cord to the coccyx
Filum Terminale
The internal portion extends from the conus medullaris to the dural sac, and the external portion extends from dural sac into the sacrum.
Where does the epidural space end?
The sacrococcygeal ligament
Risk for obese and pregnant patients when performing epidural
Batson’s plexus (epidural veins) are engorged which increases risk of vascular injury
What does the subarachnoid space contain?
CSF, Nerve roots, rootlets, and spinal cord
The terminal end of the subarachnoid space is called the ________.
Dural Sac (S2 in adult, S3 in infant)
Cranial border
Foramen magnum
Caudal border
Sacrococcygeal ligament
Anterior border
Posterior longitudinal ligament
Lateral border
vertebral pedicles
posterior borders
ligamentum flavus and vertebral lamina
What does the epidural space contain?
nerve roots, fat pads, blood vessels
What reduces the bioavailability of lipophilic drugs?
epidural fat (acts as a sink)
(bupivicaine > lidocaine and fentanyl > morphine)
The _______ nerve roots carry sensory information.
posterior (dorsal)
The ________ nerve roots carry motor and autonomic information.
anterior (ventral)
C6 innervates ——-
1st digit (thumb)
C7
2nd and 3rd fingers
C8
4th and 5th fingers
T4
nipple line
T6
Xiphoid process
T10
umblilicus
T12
pubic symphysis
L4
anterior knee
T4 (nipple line) surgery?
upper abdominal
C-section
Cystectomy
T6-7 (xyphoid process)
lower abdominal surgery
appendectomy
T10 (umbilicus)
total hip arthroplasty
vaginal delivery
TURP
L1-3 (inguinal ligament)
lower extremity surgery
L2-3
foot surgery
S2-S5
Hemorrhoidectomy
Benefits of well-executed thoracic epidural compared to lumber
-superior analgesia
-minimize surgical stress response
-reduce incidence of post op respiratory issues
-allow for early ambulation
What is the primary site of local anesthesia in the subarachnoid space?
myelinated preganglionic fibers of the spinal nerve roots
Order of which nerve fibers are blocked?
Autonomic —> Sensory —–> Motor
come back the opposite way
How many dermatomes higher is autonomic than sensory?
2-6
How many dermatomes higher in sensory than motor?
2
Factors that will affect spread in spinal anesthesia?
baricity, site of injection, patient position
factors that don’t affect spinal anesthesia spread?
barbotage, speed, bevel orientation, body habitus, gender
What are the 2 primary determinants of spread for epidurals?
Volume and level of injection
Sensory blockade is ______ dermatomes higher than motor in epidural anesthesia.
2-4
there’s not autonomic differential
_______ is the most reliable determinant of intrathecal spread when using hypo- or isobaric solution
DOSE
_________ is the most reliable determinant of intrathecal spread when using a hyperbaric solution.
Baricity
What is the 1st, 2nd and 3rd sensory modalities that are blocked in order?
- temperature
- pain
- touch or pressure
Heavy myelination
skeletal muscle and proprioception
a alpha (blocked 4th)
heavy myelination
touch and pressure
a beta (blocked 4th)
medium myelination
muscle tone
a gamma (blocked 3rd)
medium myelination
fast pain, temp, touch
a delta (blocked 3rd)
light myelination
preganglionic ANS fibers
B type (blocked 1st!)
0 myelination
slow pain, temp, touch
postganglionic ANS fibers
C type fiber (blocked 2nd)
primary drug-related determinant of block height (epidural)
LA volume
primary procedure related determinant of block height (epidural)
level of injection
primary determinant of block density
LA concentration
Greatest points of lordosis (hump)
C5 and L3
Greatest points of kyphosis (dip)
T5-7 and S2
Neuraxial opioids do NOT cause:
sympathectomy
skeletal muscle weakness
changes in proprioception
What LA reduces the efficacy of epidural opioids?
2-Chloroprocaine
