Neuraxial anesthesia physiology- Exam 1

Question 1

What is the location of spinal anesthesia?
The target of the LA?

Answer 1

Subarachnoid space
Myelinated preganglionic fibers of the spinal nerve roots

Question 2

With an epidural, the LA diffuses through the ____ ___ to reach nerve roots

It can also leak through the intervertebral foramen into the _______ area

Answer 2

• Dural cuff
• Paravertebral area

Question 3

There are 7 factors that impact the spread of the LA with spinal anesthesia, 4 of them are controllable. Name them.

Answer 3

Controllable:
** Patient position
* Baricity
* Site of injection
* Dose
**Non-controllable:
** Volume of CSF
* Increased intra-abdominal pressure (preggo / obese)
* Age (elderly)

Question 4

These 5 things do NOT affect the spread of LA with a spinal

Answer 4

-Barbotage
-Injection speed
-Bevel orientation
-Addition of vasoconstrictor
-Gender

Question 5

This is the most reliable factor affecting how far and wide the anesthetic spread when using a hypo or isobaric solution with a spinal

Answer 5

DOSE

Question 6

Why does advanced age impact the spread of LA with spinal blocks?

Answer 6

Neural nerves are more vulnerable and Less CSF

Question 7

Why does pregnancy impact the spread of LA with spinal blocks?

Answer 7

Decreased CSF volume due to increased intraabdominal pressure

Question 8

5 factors that significantly impact the spread of LA during an epidural

Answer 8

LA volume
Level of injection
LA dose
Pregnancy
Old age

Question 9

3 factors that have a small impact on the spread of LA during an epidural

Answer 9

-LA concentratoin
-Patient position
-Height

Question 10

3 factors that have no impact on the spread of LA during an epidural

Answer 10

-Additives
-Direction of the bevel of the needle
-Speed of injection

Question 11

With an epidural, if you inject in the lumbar region, the LA will mostly spread ____

Answer 11

Cephalad / up

Question 12

With an epidural, if you inject in the mid-thoracic region, the LA will spread ____

Answer 12

Both up and down

Question 13

With an epidural, if you inject in the cervical region, the LA will mostly spread ____

Answer 13

Caudad / down

Question 14

Name the order in which the nerve fibers get blocks

Answer 14

1. Preganglionic B
2. C fibers
3. A gamma and delta
4. A alpha and beta

Question 15

This refers to how different types of nerve fibers have varying sensitivites to LAs affecting the level of block achieved

Answer 15

Differential blockade

Question 16

With differential blockade, the sensory level is ___ levels higher than the motor level

Answer 16

2

Question 17

With differential blockade, the sympathetic level is ___ levels higher than the sensory level

Answer 17

2-6

Question 18

Differential blockade zones easy way

Answer 18

Sympathetic is 2-6 above
Sensory level is where you injected
Motor level is 2 below

If sensory block is at T10:
Motor is blocked at T12
Sympathetic is at T8-T4

Question 19

Which fibers are blocked the longest with neuraxial anesthesia?

Answer 19

B fibers

Question 20

Clinical progression of differential blockade

Answer 20

Question 21

With a sensory block, what is the first sensation to be blocked?

Answer 21

Temperature

Question 22

With a sensory block, what is the second sensation to be blocked?

Answer 22

pain

Question 23

With a sensory block, what is the last sensation to be blocked?

Answer 23

Touch or pressure

Question 24

What do we use to monitor a motor block?

Answer 24

The modified bromage scale

Question 25

What does a 0 mean on the modified bromage scale

Answer 25

No motor block

Question 26

You are monitoring a motor block. The patient cannot raise an extended leg but they can still move the knees and feet. What number are they on the modified bromage scale?

Answer 26

1; slight motor block

Question 27

You are monitoring a motor block. The patient cannot raise an extended leg / move the knee but they can move the feet. What number are they on the modified bromage scale?

Answer 27

2; moderate motor block

Question 28

You are monitoring a motor block. The patient cannot move the legs, knees or feet What number are they on the modified bromage scale?

Answer 28

3; complete motor block

Question 29

The modified bromage scale specifically evaluates the function of the ____ nerves. It does not assess movement above these regions

Answer 29

Lumbosacral nerves

Question 30

How does neuraxial anesthesia impact: Preload? Afterload? CO? HR?

Answer 30

Decreases Decreases Decreases Decreases

Question 31

What two cardiac reflexes may be activated with neuraxial anesthesia?

Answer 31

-Bezold Jarisch -Reverse bainbridge reflex ## Footnote Reverse bainbridge is decrease in HR in response to decreased venous return https://derangedphysiology.com/main/cicm-primary-exam/cardiovascular-system/Chapter-491/cardiac-reflexes

Question 32

This is a dangerous complication of neuraxial anesthesia that can be seen in young adults with high parasympathetic tone

Answer 32

Sudden cardiac arrest

Question 33

What 4 preventative methods can we use for spinal-anesthesia induced hypotension?

Answer 33

Vasopressors 5-HT3 antagonists (zofran) Fluid Positioning

Question 34

How does zofran prevent spinal-anesthesia induced hypotension?

Answer 34

Mitigates reflexes that cause hypotension such as the Bezold-Jarisch reflex mediated by the vagus nerve

Question 35

4 treatments for spinal-anesthesia induced hypotension?

Answer 35

Pressors Anticholinergics Fluids Position caution

Question 36

Does neuraxial anesthesia have a big impact on the pumonary system? Which patient populations do we need to use special considerations with?

Answer 36

No; minimal even with high (T4) LA spread Caution in: COPD, Pickwickian syndrome

Question 37

Innervation of the GI tract stems from __ to __

Answer 37

T5-L2

Question 38

In reference to the GI tract, which system and pathway transmits sensations of satiety/distention/nausea

Answer 38

Parasympathetic afferent

Question 39

In reference to the GI tract, which system and pathway results in tonic contractions, sphincter relaxation, peristalsis and secretion?

Answer 39

Parasympathetic efferent

Question 40

In reference to the GI tract, which system and pathway transmits sensations of visceral pain?

Answer 40

Sympathetic afferent

Question 41

In reference to the GI tract, which system and pathway inhibits peristalsis secretions and leads to sphincter contraction and vasoconstriction?

Answer 41

Sympathetic efferent

Question 42

How does neuraxial anesthesia impact the GI system's sympathetic and parasympathetic tone?

Answer 42

Reduces sympathetic tone and increases parasympathetic activity

Question 43

With neuraxial anesthesia, what does the unopposed vagal tone of the GI system result in (6 things)

Answer 43

* Relaxes sphincters * increases peristalsis * Small. contracted gut with active peristalsis * Increased GI blood flow * N/V (20% of pt) * Reduced incidence of ileus

Question 44

Sympathetic blockade above ___ affects bladder control

Answer 44

T10

Question 45

Addition of neuraxial opioids impacts the bladder by...

Answer 45

* Decrease in detrusor contraction and increase in bladder capacitance * Leads to urinary retention / incontinence

Question 46

How does neuraxial anesthesia impact the neuroendocrine response?

Answer 46

It can partially suppress (major sx) or totally block (LE sx) the neuroendocrine response