Neuraxial Flashcards
Name the 5 divisions of the spinal column. How many in each?
Cervical - 7
Thoracic - 12
Lumbar - 5
Sacrum - 5 fused
Coccyx - 4 fused
What ligament covers the sacral hiatus? Why does this matter?
sacrococcygeal ligament
This is punctured during the caudal approach of the epidural space
Order the 5 ligaments of the spinal column from posterior to anterior
Supraspinous
Interspinous
Flavum
Posterior longitudinal ligament
Anterior longitudinal ligament
Which ligaments are punctured during a midline approach for an epidural ? How about Paramedian?
Midline - Supra + Inter + Flavum
Paramedian - Flavum
Which two ligaments should never be punctured?
Posterior longitudinal ligament
Anterior longitudinal ligament
List all structures during a subarachnoid block
- Skin
- Subq
- Muscle
- Supra
- Inter
- Flavum
(Epidural Space)
- Dura mater
(Subdural Space) - Arachnoid matter
(Subarachnoid space) - Pia matter
- Spinal cord
What is Batson’s Plexus? Why does this matter?
Epidural Veins
Drains venous blood from the spinal cord
(during pregnancy these veins become engorged, causing increased risk of needle injury or cannulation)
What is the Plica MEdiana Dorsalis?
Possible band of connective tissue between Flavum and dura matter. (unsure if it exists)
Which Spinal root blocks the 1st digit (Thumb)?
C6
Which Spinal root blocks the 2nd and 3rd digits?
C7
Which spinal root blocks the Pubic Symphysis?
T12
Which spinal root blocks the nipple line?
T4
Which spinal root blocks the Anterior knee?
L4
Which spinal root blocks the Xiphoid process?
T6
Which spinal root blocks the 4th and 5th digits?
C8
Which spinal root blocks the belly button?
T10
Skin dermatomes photo
Skin dermatomes photo
What innervates face?
Trigeminal nerve (CN5)
What is the site of action for spinal anesthesia?
Bathes the nerve roots - myelinated preganglionic fibers
Local anesthetics inhibit neural transmission
What is the site of action for epidural anesthesia?
Locals must diffuse the dural cuff
Can also leak through the intervertebral foramen to enter the paravertebral area and cause multiple blocks
Which factors affect the spread during a spinal block?
Baricity of the local
Patient position
Dose
Site of injection
Volume of CSF
Density of CSF
Which factors do not affect the spread of a spinal block?
-Vasoconstrictor
-Weight
-Gender
-Orientation of bevel
-Speed of injection
-Increased intra-abdominal pressure
-Barbotage
What is the primary determinant of spread for epidural?
Volume
Which type of fibers are blocked first? Second? Third?
Autonomic
Sensory
Motor
Why does it matter on the order of blockade?
autonomic is 2-6 dermatomes higher than sensory
Sensory is 2 dermatomes higher than motor
How is a differential blockade different with epidural anesthesia?
No autonomic block with epidural
Sensory block is 2-4 dermatomes higher than motor
Order of different nerve fibers?
- Beta
- C
- Alpha - Gamma and Delta
- Alpha - alpha and beta
Function of A Alpha nerves?
Heavy myelination
Skeletal muscle and motor proprioception
Function of A beta nerves?
Touch and pressure
Heavy myelination
Function of A gamma?
Skeletal muscle tone
Medium myelination
Function of A delta?
Fast pain
Temp
Touch
Medium myelination
Function of B fibers?
Preganglionic ANS fibers
Light myelination
Function of C sympathetic fibers?
Post ganglionic ANS fibers
NO myelination
Function of C dorsal root fibers?
Slow pain
Temp
Touch
NO myelination
What are cardiovascular effects of a neuraxial anesthesia ?
Vasodilates - Venous more than arterial
Reduction on venous return, CO, BP
Bradycardia by blockage of T1-T4 cardioaccelerator fivers
Unloading of cardiac mechanoreceptors (Bezold Jarisch Reflex)
Unloading of stretch receptors in the SA node
What are respiratory effects of a neuraxial anesthesia ?
-Accessory muscle is reduced
-intercostals (decreased inspiration and expiration)
-Abdominal muscles (Ability to cough and clear secretions)
-Apnea is from brainstem hypoperfusion, not phrenic nerve block
-Careful in COPD
What are the neuroendocrine effects of a neuraxial anesthesia ?
-Blocks stress response
Reduces catecholamines, renin, angiotensin, glucose, thyroid stimulating hormone, and growth hormone
What are GI effects of a neuraxial anesthesia ?
Neuraxial blocks sympathetic tone which increases parasympathetic tone in the gut
-Increases peristalsis, relaxes sphincters
What are liver and kidney effects of a neuraxial anesthesia ?
As long as systemic BP is maintained, there is NO effect
What are risks with coagulopathy and neuraxial anesthesia ? Labs?
Spinal or epidural hematoma
Plt < 100,000
PT, aPTT and or bleeding time twice the normal value
Which valve lesions are contraindicated with neuraxial anesthesia?
Aortic Stenosis
Mitral Stenosis
Hypertrophic Cardiomyopathy
What is the risk of neuraxial anesthesia and increased ICP ?
Sudden change in CSF can cause brain herniation
Relationship between neuraxial anesthesia and MS?
Should be okay but use lower dose and warn the patient their symptoms might be exacerbated
Specific gravity of CSF?
1.002-1.009
What is baricity? How does it affect local?
Describes the density of the local
-Isobaric is similar to CSF
-Hyperbaric is more dense than CSF
-Hypobaric is less dense than CSF
What solution is usually hyperbaric? What will happen?
Dextrose is usually hyperbaric
The solution will sink
What solution is usually hypobaric? What will happen?
Water (hypO)
The solution will rise
What solution is usually isobaric? What will happen?
Saline
Solution will remain in place
What solution is an exception?
Procaine 10% in water
This will be hyperbaric because there are so many molecules
What is a saddle block?
If the patient stays sitting with a hyperbaric solution
Solution sinks and coats the sacral nerve roots
If you lay a patient down with a hyperbaric solution, what will happen?
The solution will settle and pool in the sacrum and thoracic kyphosis
Hyperbaric photo
Hypobaric photo
Where will hypobaric solution settle?
Highest point in the spinal canal
Do not give to sitting up patient. It will rise to the head
What is the name of the cutting needle?
Cutting - Quincke
What is the name of the non cutting needles?
Pencil - Sprotte
Pencil - Whitacre
Rounded -Green
Pros and Cons of cutting?
Pros - less force
Cons - Less tactile, easily deflected, more likely to injure cauda equina, higher risk of PDPH
Pros and Cons of non cutting
Pros - More tactile, less likely to deflect, less likely to injure cauda equina, lower risk of PDPH
Cons- Need more force
Three different types of epidural needles ?
Crawford - 0 degrees
Hustead - 15 degrees
Tuohy - 30 degrees
Alphabetical order