Exam 1- Neuraxial Principles (5/30/23) Flashcards
1
Q
What are the two major components of regional anesthesia?
A
- Central Neuraxial Blocks
- Peripheral Nerve Blocks
2
Q
What are the two components of Central Neuraxial Anesthesia?
Which one is harder to perform?
A
- Spinal Anesthesia
- Epidural Anesthesia (This one is harder to perform, it takes skills.)
3
Q
Will you expect to see CSF during epidural blocks?
A
No. CSF should not be expected in epidural blocks.
CSF is expected in spinal blocks.
4
Q
What ligaments (in order) will the needle pass through to get to the epidural space?
A
- Supraspinous Ligament
- Interspinous Ligament
- Ligamentum Flavum
5
Q
Spinal Anesthesia is the injection of local anesthetic (LA) into the ____________ space.
A
- Subarachnoid
6
Q
What are two other names for Spinal Anesthesia?
A
- Subarachnoid Block (SAB)
- Intrathecal Block
7
Q
Are subarachnoid blocks used primarily as adjunct agents or as the sole anesthetic technique?
A
SABs can be used both as the primary anesthetic plan and also as adjuncts.
8
Q
What procedures commonly require a SAB?
A
- C-section
- Lower extremity surgery
- Abdominal Surgery (Lower/Upper)
9
Q
Differentiate the onset of action between a spinal block and an epidural block.
A
Spinal Block: Rapid Onset (5 min)
Epidural Block: Slow Onset (10-15 mins)
10
Q
Describe the spread of LA between a spinal block and an epidural block.
A
Spinal Block: Higher than expected; may extend extracranially.
Epidural Block: As expected, can be controlled w/ volume of LA.
11
Q
Which type of block tends to extend cephalad?
A
Spinal Block: Higher than expected; may extend extracranially.
12
Q
Which type of block (spinal or epidural) is much more segmental in nature?
A
Epidural Block = Segmental
13
Q
Which type of technique (spinal or epidural) will result in much greater motor neuron blockade?
A
Spinal Block = Dense motor block
14
Q
Is hypotension more likely to occur between a spinal block or an epidural block?
A
- Spinal Block
15
Q
For SAB, the _______ effect is usually 2 spinal segments cephalad of the sensory block.
A
- SNS
16
Q
For SAB, the _______ effect is 2 spinal segments below the sensory block.
A
- Motor
17
Q
What are your phrenic nerves?
A
- C3 nerve fiber
- C4 nerve fiber
- C5 nerve fiber
18
Q
What LA discussed in class is used for a “walking” epidural.
A
- Ropivacaine
Ropivacaine provides a very segmental block
19
Q
What are your cardiac accelerator nerves?
A
T1 - T4
20
Q
What term was used in class to describe antagonized sympathetic nerve fibers secondary to local anesthetics?
A
- Sympathectomy
This usually results in hypotension and bradycardia.
21
Q
Differentiate the duration of action between a spinal block vs an epidural block.
A
Spinal: Limited and fixed (one-shot)
Epidural: Unlimited (Catheter in place w/ LA infusion)
22
Q
Differentiate the level of placement between a spinal block vs an epidural block.
A
Spinal Block: Start at L3-L4, L4-L5, L5-S1
Epidural Block: Any Level
Although an epidural can be performed at any level, residents will start at L3-L4.
23
Q
How many attempts are permitted for a spinal/epidural block?
A
- Three
24
Q
Differentiate the dosing between a spinal block vs an epidural block.
A
Spinal Block: Dose-base
Epidural Block: Volume-base
25
What is the max amount (volume) of LA for a spinal block vs epidural?
Spinal Block: 3 mL
Epidural Block: 20 mL
26
Differentiate the concentration of LA between a spinal block vs an epidural block.
Spinal Block: Concentrated and fixed
Epidural Block: Varies
27
Differentiate the LA Toxicity between a spinal block vs an epidural block.
Spinal: No
Epidural: Yes (Higher risk of LA entering the bloodstream due to bilateral veins on the spine.)
28
Which LA discussed in class is the most sensitive to the heart?
* Bupivacaine
29
What should be done during a Bier Block procedure if IV Bupivacaine is accidentally administered instead of Lidocaine?
* Leave the tourniquet in place and let the bupivacaine be absorbed.
* Do not deflate the cuff unless you want V-tach/ V-fib.
30
Differentiate how gravity influences a spinal block vs an epidural block.
Spinal Block: Yes, there will baricity
Epidural: No, unless the needle punctures the dura ("wet tap").
31
Differentiate the manipulation of dermatome spread after dosing between a spinal block vs an epidural block.
Spinal: Positional Change depending on baricity (Iso, Hyper, Hypobaric)
Epidural: Incremental dermatome spread based on volume. 1-2 mL per segment.
32
Neuraxial anesthesia can reduce these 6 adverse events.
* **Bleeding**
* Narcotic usage
* Postop Illeus
* Thromboembolic events
* PONV
* Respiratory complications
33
What are the other benefits of Neuraxial Anesthesia?
* Great mental alertness
* Less urinary retention
* Quicker to eat, void, ambulate
* **Quicker PACU discharge (use Lidocaine)**
* Preemptive anesthesia
* Blunts stress response from surgery
34
What are the indications of spinal anesthesia?
* Surgical procedures involved with Lower abdomen, Perineum, and Lower extremities (Knees/Hips)
* Cesarean Delivery (**for elective and stat cases only**)
35
What anesthesia would be indicated if the surgeon needs the patient to be still?
* General Anesthesia
*Important to communicate with surgeon about the plan of care.*
36
What anesthesia would be indicated if there is an emergency Cesarean delivery?
* General Anesthesia (Rapid Sequence Induction)
37
What are absolute contraindication of spinal anesthesia?
* Coagulopathy (risk of epidural hematoma)
* Sepsis
* Patient refusal/ cooperation/ mental competency/ age/ lack of informed consent
* Evidence of dermal site infection
* Hypovolemia (Already prone to sympathectomy)
* Pre-existing spinal cord disorder (intraspinal mass)
* Valvular disease (Aortic/Mitral Stenosis)
38
What is the problem with aortic stenosis when performing spinal anesthesia?
* Decrease SVR resulting in hypotension
**Don't not perform spinal anesthesia if the patient has severe aortic stenosis <1.0 cm2**
39
Absolute contraindication coagulopathy lab values for spinal anesthesia.
INR
Platelets
* INR > 1.5
* Platelet < 50-100K (consider trends)
40
What are relative contraindications of neuraxial anesthesia?
* Deformed spinal column (ie: kyphoscoliosis)
* Pre-existing disease of the spinal cord (MS)
* Chronic HA/ backache (take a baseline assessment)
* Inability to perform SAB after 3 attempts
41
How many vertebrae does a human have?
* 33
42
How many pairs of spinal nerves does a human have?
* 31 pairs
43
The inferior angle of the Scapula is parallel to which vertebrae?
* T7
44
How many cervical vertebrae are there?
How many pairs of cervical spinal nerves are there?
* 7 cervical vertebrae
* 8 cervical spinal nerve pairs
45
Is caudal anesthesia an epidural or spinal block?
* Epidural block
46
Where is the insertion point for a caudal anesthesia?
* Sacral Hiatus
*The sacral hiatus provides an opening into the sacral canal, which is the caudal termination of the epidural space.*
47
What are the bony prominences on either side of the hiatus and aid in identifying that landmark?
* Sacral Cornu
48
Where are the high points and low points when a patient is in a supine position?
* High Points (Apex): C3 and L3
* Low Points (Trough): T6 and S2
49
If a LA that is a hyperbaric solution is administered at L3. When the patient is supine where will the LA travel in the cephalad and caudal area?
Cephalad: T6
Caudal: S2
50
What is the orientation of the lumbar spinous process?
* Relatively straight
* Posterior/horizontal orientation
51
What is the orientation of the thoracic spinous process?
* Pointing caudally
* Posterior/ oblique orientation
52
Adipose tissue and blood vessels are located at the ________ aspect of the epidural space.
* Lateral
*When blood is encountered during needle insertion, most likely, the needle is lateral.*
53
What is the distance from skin to ligamentum flavum for 50% of the patient population?
What is the distance from skin to ligamentum flavum for 80% of the patient population?
* 4 cm
* 4 to 6 cm
54
What percentage of people have their spinal cord end at T12?
What percentage of people have their spinal cord end at L1?
What percentage of people have their spinal cord end at L3?
* 30% end at T12
* 60% end at L1
* 10% end at L3
**For board purposes, L1 is the end of your spinal cord.**
55
Where does the spinal cord end for children?
* L3
56
Where does the dural sac end in an adult?
* S2
*This is where your subarachnoid space ends*
57
Name the blood supplies of the spinal cord.
* One anterior spinal artery
* Two posterior spinal arteries
* Segmental spinal arteries
58
Where does the anterior spinal artery originate from?
Where do the two posterior spinal arteries originate from?
Where do the segmental spinal arteries originate from?
* Anterior spinal artery originates from the vertebral artery
* Posterior spinal arteries originate from the inferior cerebellar artery
* Segmental spinal arteries originate from the intercostal and lumbar arteries
59
The two most common drugs used to treat hypotension in anesthesia.
* Neosynephrine (use when HR is high w/ low BP)
* Ephedrine (use with bradycardia w/ low BP)
60
What is the caveat of using ephedrine?
* Tachyphylaxis
61
What is the outermost layer of the spinal meninges?
* Dura mater (thickest)
62
Where does the dura mater start and end?
* Start at the foramen magnum
* Ends in S2 (fuses with filum terminale)
63
The subarachnoid space lies between the ________ mater and the _______ mater and contains the CSF.
* Arachnoid mater (delicate, avascular membrane)
* Pia mater
64
Which meninges is adherent to the spinal cord and comprise a thin layer of connective tissue cells interspersed with collagen
* Pia mater
65
What is the amount of CSF in adult humans?
* 100 to 160 mL
66
What is the CSF production rate?
* 20 to 25 mL/hr
67
The entire CSF volume is replaced every ____ hours.
* 6 hours
68
A decrease in CSF is usually secondary to what factor?
What is the clinical significance of lower CSF volume?
* Abdominal pressure (ascites, obesity, pregnancy)
* The pressure will disperse the CSF volume
* Clinical Significance: Lower CSF volume = small amount of LA
69
The area of cutaneous sensation supplied by a spinal nerve is anatomically identified as it passes through an intervertebral foramen.
* Dermatome
70
Dermatome region related to T10.
* Umbilicus
71
Dermatome region related to T4.
* Nipple Line
72
Dermatome region related C6.
* Thumb
73
Dermatome region related C6, C7, and C8.
* Hand
74
Why do hypotension and vomiting occur during a C-section?
* Fundal pressure will compress the vena cava, resulting in hypotension and emesis.
*Spinal anesthesia will be administered at T4 due to the fundal pressure.*
75
The patient's thumb is numb after using a hyperbaric LA spinal block. To prevent respiratory depression, how should the patient be positioned?
* Raise the head of the bed
* Start O2 nasal cannula at 1-2 L/min
*Numb thumb is C6; raise the HOB so that LA doesn't travel to C5 (phrenic nerve).*
76
Where is the Tuffier's (Intercristal) Line?
* A horizontal line that connects the highest points of the iliac crests that serve as an important marker to determine the puncture level
* This will indicate that you are between L3 and L4
77
What are the purposes of using LA additives/ adjunct agents in neuraxial anesthesia?
* Prolong the block
* Intensify the block
* Increase speed of onset
78
What factors determine the type of LA to use in a SAB?
* Type of surgery (consider the position of the pt)
* Length of surgery (<150 mins)
* Surgeon (look at hospital data)
79
If surgery is going to last 3 hours, is spinal anesthesia recommended?
* No, the maximum duration of spinal anesthesia is 150 mins with epinephrine
*A better option is to do general anesthesia for longer cases.*
80
If you give 2 mL of 0.75% bupivacaine, how many mg is that?
* 15 mg
0.75% Bupivacaine
% is equal to grams/ 100 mL
0.75 grams/ 100 mL
750 grams/ 100 mL
7.5 grams/ mL
15 grams/ 2 mL
*Shortcut: 0.75% move decimal one place to the right to make it 7.5 mg/mL*
81
How much epinephrine is in 1 cc if the concentration is 1:100,000?
* 10 mcg/mL
Epinephrine 1:100,000
1 g of epinephrine in 100,000 mL
1000 mg/ 100,000 mL
1 mg/ 100 mL
1000 mcg/ 100mL
10 mcg/ mL
*Shortcut: Divide 1,000,000 by 100,000 to get 10 mcg/ mL*
82
Local Anesthetic Dosing/ Duration Chart
83
Name the three chemical structures that make up a LA.
* Aromatic Ring
* Ester or Amide Intermediate Linkage
* Tertiary Amine
*LAs that are amides have two "i's"*
84
MOA of LA.
* Block Na+ channels from the **inside of the cell** to block transmission of an action potential.
85
What adjunct agent can intensify the blockade of a spinal block?
* Opioids
* Sufentanil, Fentanyl, Morphine
*Opioids do not provide an extension of duration, just an increase in density and provide analgesia*
86
What adjunct agent can improve a spinal block's density, duration, and analgesia?
* Alpha-2 agonist
* Dexmedetomidine (IV/ intrathecal), Clonidine
*This could be a better option than opioids.*
87
What adjunct agent only extends the duration of a spinal block?
* Vasopressors
* Epinephrine and Phenylephrine
88
Name the dosage of the following adjunct agent for a spinal block:
Morphine
Fentanyl
Sufentanil
* Morphine 100-400 mcg (24 hrs)
* Fentanyl 10-25 mcg
* Sufentanil 2.5-10 mcg
89
Name the dosage of the following adjunct agent for an epidural block:
Morphine
Fentanyl
Sufentanil
* Morphine 3-5 mg (24 hrs)
* Fentanyl 50-100 mcg
* Sufentanil 10-25 mcg
*Higher doses required when given by the epidural route*
90
Which opioid is used in spinal anesthesia has a long duration of action, slow clearance, and is hydrophilic?
* Morphine
*Watch out for delayed respiratory depression, slow spread into the intrathecal space.*
91
If morphine was used as an adjunct agent in spinal anesthesia, what needs to be communicated with the PACU nurse?
* Watch for delayed respiratory depression
* Continuous Pulse Ox
92
What is the antidote for morphine?
What needs to be considered?
* Narcan
* Narcan's effect is shorter acting than the effects of morphine. Reversal may be short-lived.
