NEURAXIAL Flashcards
What are the 5 divisions of the spinal column and how many vertebrae are present in each?
33 vertebrae
C5 - T12 - L5 - S5 - C4
What are the anatomic borders of the facet joint?
Formed by the superior articular process of one vertebra and the inferior articular process of the vertebrae directly above.
Injury to the facet joint can compress the spinal nerve that exits the respective intervertebral foramina causing pain and muscle spasm along the associated dermatome
Order the 5 ligaments of the spinal column from posterior to anterior
Supraspinous - interspinous - ligamentum flavum - PLL - ALL
List all of the structures and spaces between the skin and spinal cord as they would be encountered during a subarachnoid block
skin - SQ - supraspinous - interspinous - ligamentum flavum - epidural - dura - subdural - arachnoid - subarachnoid - pia mater - spinal cord
What are the boundaries of the epidural space?
Cranial border = foramen magnum
Caudal border = Sacrococcygeal ligament
Anterior = PLL
Lateral = vertebral pedicles
Posterior = ligamentum flavum, vertebral lamina
What happens when you inject LA into subdural space during SAB? vs epidural
Epidural = high spinal w/delayed onset (15 - 20m)
Spinal = failed spinal
What is the plica mediana dorsalis, and what is its significance?
Controversial existence
Band of CT that courses between the ligamentum flavum and the dura mater. Conceivably creates a barrier that impacts the spread of meds in epidural space. Possible etiology for difficult epidural placement as well as unilateral epidural block
Important dermatome levels
C6 = thumb
C7 = pointer, middle
C8 = ring, pinky
T4 = nipple
T6 = xiphoid process
T10 = umbilicus
T12 = pubic symphysis
L4 = anterior knee
Site of action for spinal vs. epidural
Spinal = myelinated preganglionic fibers of the spinal nerve roots
Epidural = infuse thru the dural cuff before they can block the nerve roots. They also leak through the intervertebral foramen to enter the paravertebral area.
What contributes to the spread of LA in subarachnoid space?
Patient position
Baricity
Dosing
Site of Injection
Volume of CSF
Density of CSF
What is the primary determinant for spread of epidural anesthesia
Volume
Differential blockade for spinal anesthesia
1st = autonomic (+2 - 6 levels above motor)
2nd = sensory (+ 2 levels above motor)
3rd = motor
Differential blockade for epidural anesthesia
Only sensory & motor differential
Sensory is 2 - 4 dermatomes higher than motor block
A-Alpha
Skeletal muscle motor & proprioception
Blocked last
Heavily myelinated
12 - 20 um
B-Beta Fibers
Touch, Pressure
Blocked last
Heavy myelination
5 - 12 um
Gamma Fibers
Skeletal muscle tone
Blocked third
Medium myelination
3 - 6 um
Delta
Fast pain, temperature, touch
Blocked third
medium myelination
2-5 um
B Fibers
Preganglionic Fibers
Blocked 1st
Light myelination
3
C Fiber Sympathetic
Sympathetic = postganglionic ANS
Blocked 2nd
No myelination
0.3 - 1.3
C Fiber
Slow pain, temperature, touch
Blocked 2nd
No myelinaiton
0.4 - 1.2
Respiratory effects of neuraxial
Impaired intercostal muscles (inspiration and expiration)
Abdominal muscle (ability to cough and clear secretions)
If there is apnea, it’s d/t hypoperfusion
GI function & neuraxial
The gut receives PSNS from CN10 and SNS from sympathetic chain T5 - L2. Neuraxial increases PSNS = sphincters relaxed, peristalsis increased
What is the risk of neuraxial anesthesia with the patient with a coagulopathy? What labs?
Plt < 100
PT, aPTT, bleeding time 2x normal
Cardiac pathologies that are a c/i
AS
MS
HCM
