Exam 1 Spinal & Epidural Neuraxial Anesthesia [5/30/24] Flashcards
What is the order of the meningeal layers from outter to inner?
- Dura Mater:The outer most layer.
- Arachnoid Mater:The middle layer.
- Pia Mater:The inner most layer that directly covers the SC.
S29
Spinal Anesthesia is also called?
- Subarachnoid block
- Intrathecal
S29
List the 3 key spaces discussed in class.
- Epidural space
- Subdural space
- Subarachnoid space
S30
Where is the epidural space?
What does it contain?
- Located outside/before the dura mater.
- Contains fat and small blood vessels (epidural veins).
S30
What is the subdural space?
- A potential space between the dura mater and the arachnoid mater.
S30
Where is the subarachnoid space located?
What does it contain?
- Between the arachnoid mater and the pia mater.
- Filled with cerebrospinal fluid (CSF), which cushions and protects the spinal cord
- This is where we want the tip of the needle for spinal anesthesia.
S30
What 2 things might happen if the subdural space is hit?
- if its spinal it wont work
- if its epidural, will have high spinal block.
S30
The epidural space is located around the spinal cord and has
specific boundaries defined by spinal structures. What are the boundaries of the Epidural Space?
- Cranial Border: At the top,near the base of the skull (foramen magnum).
- Caudal Border:At the bottom,near the ligament connected to the coccyx (sacrococcygeal ligament).
- Anterior Border:In front,lined by the posterior longitudinal ligament along the vertebrae.
- Lateral Borders:On the sides,marked by the bony projections of the vertebrae (vertebral pedicles).
- Posterior Borders:At the back,framed by ligamentum flavum and the bony plates of the vertebrae (vertebral lamina).
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Where does the epidural space start and end?
Clinical relevance?
- Starts: Foramen mangum
- Ends: S5
- Wide range you can cover meaning we can administer the epidural anesthesia from foramen magnum to S5 . Can do epidural anesthesia in thoracic, lumbar, caudal.
S31
- what is in front of the epidural space?
- what is the posterior border of epidural space?
- Posterior ligament
- then we have the body of the vertebra and then the anterior ligament.
- the anterior portion of the epidural space is one of the ligaments that we dont want to touch [this is the posterior ligament]
- Ligamentum flavum and vertebral lamina
S31
List the contents of the epidural space
Contains:
* nerves
* fatty tissue
* lymphatics
* blood vessels
S32
What is the role of the contents of the epidural space?
- Aids in drug absorption.
- Fatty tissue in this area can absorb and decrease the availability of certain drug
- Ex: bupivacaine is absorbed more than lidocaine or fentanyl or morphine
S32
- Epidural vein is also called?
- What are the characteristics of the epidural vein?
- Batson’s Plexus
- Valveless and form a plexus draining blood from the cord and its linings
- Density of veins increases laterally
- Engorged under conditions like obesity or pregnancy, increasing the risk during needle procedures in this area.
S32
If getting blood, then you are injecting laterally and not midline!
Plica Mediana Dorsalis
- Plica Mediana Dorsalis is for spinals or epidurals?
- What is it?
- What is its impact?
- Epidurals only.
- Thought to be a band of connective tissue located between the ligamentum flavum and the dura mater
- If it exists, it might act as a barrier within the epidural space which could affect how medications spread when injected into the epidural space.
What is the clinical relevance of Plica Mediana Dorsalis
- Catheter Insertion: The plica mediana dorsalis is sometimes considered a possible reason for complications in placing an epidural catheter.
- Unilateral Blocks: It might also play a role in cases where an epidural does not equally affect both sides of the body.
S33
How much catheter should be left in the epidural space?
3-5cm
S33
If giving sufentanyl to a laboring mother, take caution becuase?
It travels and crosses the placenta resulting in low APGAR scores.
S33
What can we do for one sided blocks?
- Positioning
- Pull the catheter out a little. Be cautious that the catheter is still in the epidural space.
- Pull out and start over again.
- Talk to the pts about this in informed consent.
S33
Subarachnoid Space
Where is the subarachnoid space?
What does it contain?
- Located deep to the arachnoid mater| in between arachnoid and pia mater.
- Contains cerebrospinal fluid (CSF), nerve roots, and the spinal cord itself.
S34
This space is the primary target when performing a spinal anesthetic procedure
Subarachnoid Space
S34
If the needle is advanced too far anteriorly when doing spinals what are possible layers that are passed
- pia mater
- spinal cord
- the posterior longitudinal ligament before reaching bone.
S34
What are the characteristic Sensation when performing a spinal anesthesia.
- During spinal anesthesia, a characteristic “pop” is often felt when the needle passes through the outer membrane, the dura mater.
The subdural space is a ____ located b/w which 2 layers around the spinal cord?
Potential space
dura mater (outer layer) and arachnoid mater (middle layer)
S35
If we accidentally place an epidural in the subdural space what would the clinical effect be?
- “high spinal” effect meaning the medication affects a larger area than intended
S35
If we inadvertently place a spinal dose in the subdural space what would the result be?
failed spinal block
(it wont work!!!)
S35
The Dura mater extends from ____ to ____ .
Foramen magnum to the dural sac (which ends at S2 in adults and S3 in infants)
S36
Which layer of meninges is the 1st layer encountered by the needle after advancnig through the epidural space?
Dura Mater
S36
What type of tissue makes up the arachonid mater?
connective tissue
S36
T/F
the pia mater lacks vasculature
FALSE!
The pia mater is HIGHLY vascular
S36
Where is the pia mater located?
Should the spinal needle punture this layer of meninges?
this innermost layer directly covers the spinal cord
NO!! it should NEVER be punctured as it is directly attached to the surface of the spinal cord
S36
How mant spinal nerves do we have total? at each level of the spinal cord?
31 spinal nerves!
C-8
T-12
L-5
S-5
Coccyx-1
S37
Which of the cervical spine nerves is an exception in terms of where it exits the vertebra?
C8 nerve exits BELOW C7 whereas all other cervical spine nerves exit above the vertebra they are named for.
Where do the spinal nerves exit for thoracic, lumbar, sacral, and coccyx nerves?
below the vertebra they are named for
S37
Each spinal nerve is formed by the joining of what?
2 nerve roots:
* Anterior/ventral nerve root (which carries motor and autonomic information from the SC to the body)
and
* Posterior/dorsal nerve root (which carries sensory information from the body to the SC)
S37
What is a dermatome?
An area of skin that receives sensory nerves from a single spinal nerve root
S38
T/F
While a dermatome may physically appear to align w/ a certain part of the spine, it is actually connected to a different spinal nerve root
TRUE
S38
The umbilicus looks like it should be served by the ____ nerve, but its actually served by ____
L3
T10 (actual)
S38
L1,2,3,4 dermatomes cover
anterior and inner surface of the lower limbs
S39
L4,5 S1 dermatomes cover
foot
S39
L4 dermatome covers
medial side of great toe
S39
S1,2 L5 dermatome covers
posterior and outer surface of lower limbs
S39
S1 dermatome covers
Lateral margin of foot and little toe
S39
S2,3,4 dermatome covers
Perineum
S39
T10 dermatome covers
Umbilicus
S39
T12 dermatome covers
Inguinal or groin regions
S39
C5 dermatome covers
Clavicles
S39
C5,6,7 dermatomes cover
lateral parts of upper limbs
S39
C8, T1 dermatomes cover
Medial sides of upper limbs
S39