3 - Neuraxial Anesthesia Flashcards
1
Q
How many vertebrae are in the spinal column?
A
33
2
Q
Number of vertebrae:
Cervical
Thoracic
Lumbar
Sacral
Coccygeal
A
7 cervical
12 thoracic
5 lumbar
5 sacral (fused)
5 coccygeal (fused)
3
Q
The epidural space extends from ____ to ______
A
foramen magnum
sacral hiatus
4
Q
Which vertebrae have no epidural fat?
A
Cervical
5
Q
Dura Mater
A
Thickest, outermost meningeal layer
6
Q
Arachnoid Mater
A
Laminar layer over the inner surface of the dura
Trabecular spider formations connect the laminar layer to the pia mater
7
Q
Does the dura or arachnoid membrane most impede drug movement through the meninges?
A
Arachnoid
8
Q
Is CSF primarily in the subdural or subarachnoid space?
Why?
A
Subarachnoid
low permeability of arachnoid mater keeps it from migrating out into the subdural space
9
Q
What percentage of CSF is water?
A
99%
10
Q
Adult total volume of CSF
A
100-160 ml
11
Q
What is the main production site of CSF?
A
Parenchymal Capillaries of the brain and spinal cord
12
Q
Which direction does CSF flow?
A
Not unidirectional
Transmitted cardiac oscillations produce local mixing
13
Q
Where is CSF absorbed?
A
Parenchymal capillaries of the brain and spinal cord
14
Q
Which grows faster in a fetus: the spinal cord or the vertebral cloumn?
A
The vertebral column
15
Q
Where does the spinal cord end in adults?
Newborns?
A
L1
L3
16
Q
How are spinal nerves and dermatomes named in cervical regions?
All other regions?
A
Lower vertebrae of the foramen they pass through
Upper vertebrae of the foramen they pass through
17
Q
What is the cauda equina?
A
the lumbar and sacral spinal nerves that extend beyond the tip of the spinal cord
18
Q
When using hyperbaric drugs, you should position the operative side ________
A
down
19
Q
When using isobaric or hypobaric drugs, you should position the operative side _______
A
UP
20
Q
For C/S spinal lying down, which side should the patient lie on?
A
Right side
21
Q
Which is usually larger: epidural or spinal needle?
A
Epidural
22
Q
What length of catheter should be inserted into the epidural space?
A
5 cm
23
Q
The two most important factors that determine the spread and duration of subarachnoid anesthesia are
A
Density and Dose
24
Q
How is hyper/hypo/isobaric determined?
A
It’s the ratio of two densities:
Dnesity of the CSF
Density of the drug
25
Hyperbaric solutions are ______ dense than CSF
More
26
How are local anesthetics made hyperbaric?
Mixed with dextrose
27
In a supine patient, hyperbaric anesthetics will flow to
The upper thoracic region
28
Vasopressors prolong the effect of _______ in intrathecal anesthesia, but not \_\_\_\_\_\_\_\_
tetracaine
lidocaine, bupivicaine
29
How does intrathecal precedex effect duration?
Prolongs the duration of subarachnoid anesthesia and analgesia
30
What amount of fentanyl is optimal as an adjuvant to spinal analgesia?
Smaller doses are just as effective and cause less itching
31
How is epidural spread effected by age?
Spreads further in older people
May worsen hypotension
32
In epidurals, the large the dose, the _________ spread
larger
33
What is the effect of using sodium bicarb as an adjuvant
Raises the pH, which increases non-ionized circulating amount
Decreases the speed on onset
Inreases the density of block
34
What is the effect of using A2 agonists as adjuvants?
Epinephrine decreases systemic absorption of the drug
Precedex/Epi/Clonidine improve speed of onset and duration
35
Who do A2 agonists improve the analgesia of a block?
Stimulation of A2 receptors produces analgesia
36
Most common complication in obstetric epidural management
Accidental injection of drugs into intrathecal space
37
What abnormal things are you looking for when test dosing an epidural with lidocaine?
Tingling in feet at 2-3 minutes
Motor loss at 3 minutes
38
Unrecognized subdural injection would cause what?
Excessive epidural block
39
Subarachnoid anesthesia occurs mostly in the \_\_\_\_\_\_\_\_
Spinal nerve roots
40
How does neuraxial block effect MAC?
Decreases MAC of inhaled volatile gases
41
What effect does neuraxial anesthesia have on sedatives?
Potentiates their action
Also causes sedation on its own
42
Why do patients with neuraxial anesthesia lose sensation to a greater degree than motor use?
Sensory fibers are thinner than the large, thick motor fibers
43
A patient with a sensory block at T10 may have a sympathetic block \_\_\_\_\_\_\_
Much higher
smaller fibers
44
Sensitivity of fibers to neuraxial anesthesia:
Motor
Sensory
Sympathetic
small
intermediate
large
45
What happens to CO and SVR after intrathecal block?
Increases
Decreases
46
What vertebral level is sympathetic stimulation of the heart?
What would happen if it was blocked?
T1-T4
Disproportionate vagal response ----\> severe bradycardia
47
What are the differing effects of using phenylephrine vs ephedrine for neuraxial hypotension?
Phenylephrine will not increase the heart rate, and in fact will decrease it
Ephedrine will increase the heart rate
48
What are four ways to alleviate N/V with spinal anesthesia?
Fix hypotension
Administer oxygen
Fluids
Zofran
49
Why does patients with neuraxial anesthesia get nauseated?
Increased vagal activity increases peristalsis
Hypotension causes hypoperfusion of the vomiting trigger chemoreceptor in the medulla
Opiates, when included in the injection
50
A patient with a Thoracic block and normal respiratory function may still be prone to aspiration. Why?
The abdominal muscles are crucial in coughing
51
Postdural puncture headaches usually effect the _____ and _____ regions of the head
front
occipital
52
Which needles are pencil point?
Whitaker
Spratte
53
What needle is a cutting needle?
Quincke
54
How often is a blood patch effective in fixing PDPH?
95%
55
When does PDPH usually develop
24-72 hours after dural puncture
56
Why does hearing loss sometimes occur with spinal anesthesia?
Decreased CSF pressure reduces the function of the inner ear
57
When does hearing reduction from spinal anesthesia usually resolve?
Within 1 month
58
Cervical and thoracic vertebrae have spinous processes that \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
angle acutely in a caudal direction
Very tight construction and angles, making needle insertion difficult
59
Why is the lumbar area easier to cannulate?
spinous processes shorter and broader with posterior orientation
Relatively large gaps between processes
60
What is the average distance from skin to lumbar epidural space?
5cm
61
Where is the epidural space largest?
midline midlumbar region
62
Why are midline epidural approaches preferred?
Epidural space is larger anterior to posterior than it is laterally
The plexus is most prominent in the lateral portion
63
what happens to epidural veins in pregnant women?
Engorged d/t increased abdominal pressure
64
What is a differential block?
Iterrupts autonomic transmission but not sensory or motor
65
A sympathetic block can be as much as ______ above the sensory blockade
six dermatomes
66
Do patients with neuraxial anesthesia have a higher or lower incidence of urine retention that general anesthesia?
Lower
67
What is selective anesthesia?
small doses of local injected into only the nerve roots inolved in the surgical field
Usually CSE
68
What type of local anesthetic is used in prone cases?
Hypobaric
69
Conducting a spinal in a patient with increased ICP may cause
Brain herniation
70
Which musculoskeletal deformity is a risk factor for CNB complications?
Osteoporosis
71
What is a double crush phenomenon?
CNB peripheral neuropathy on top of Pre-existing neuropathy
72
Why is garlic a concerning herbal medication?
How long should it be d/c'd prior to sx?
Inhibits platelet aggregation
Increases fibrinolysis
7 days
73
Why is ginkgo a concerning herbal medication?
How long should it be d/c'd prior to sx?
inhibits platelet activation
36 hours
74
Why is ginseng a concerning herbal medication?
How long should it be d/c'd prior to sx?
lowers blood glucose
increases PT/PTT
34 hours
75
What is the most common pathogen associated with epidural abscesses?
S. aureus
76
What is the best test for suspected epidural hemorrhage or abscess?
MRI
77
Which type of heart failure is a relative contraindication to CNB?
preload dependent (hypertrophic, severe Ao Stenosis)
These patients can't tolerate even short periods of bradycardia or decreased preload from vasodilation
78
What is specific gravity
density of a substance compared to water
79
What factors can increases the specific gravity of CSF?
Hyperglycemia
Uremia
Age
80
What factors can decrease the specific gravity of CSF?
temperature (increased temp)
Bilirubin in the CSF (from jaundice/liver fx)
81
What is the ratio of specific gravity of an isobaric anesthetic to CSF
1
82
What is the baricity of a hypobaric solution?
Hyperbaric?
\< 0.999
\> 1.0015
83
Name three highly protein bound drugs.
Do they have a long or short duration?
Tetracaine
Bupivicaine
Ropivicaine
Long
84
Name two low protein-bound drugs.
Do they have a long or short duration?
lidcocaine
mepivicaine
Short
85
To minimize the risk of PDPH, the epidural needle should be turned \_\_\_\_\_\_\_\_\_
with the bevel parallel to dural fibers
86
How far should a CSE catheter be threaded?
2-3 cm
87
To avoid PDPH with CSE, how long should the catheter be left in place if possible?
40 hours
88
Cauda Equina Syndrome
persistent paralysis of the cauda equina nn
lower extremity weakness
bowel and bladder dysfunction
89
Transient Neurologic Syndrome
pain originating in the gluteal region radiating to both lower extremities
spontaneously resolved within 10 days
90
Use of spinal lidocaine in CSEs is associated with which two syndromes?
cauda equina
transient neurologic
91
The sympathetic nerve fibers that innervate the heart are called the \_\_\_\_\_\_\_
cardiac accelerators
92
What is a 5-HT3 drug?
Why are they used to prevent SIH?
ondansetron
given prophylactically
thought to block the reflexive bradycardia and hypotension caused by sympathetic blockade
93
In managin SIH when should ephedrine be used?
Phenylephrine?
bradycardia
normal or tachycardia
94
Ephedrine effects _______ receptors
phenylephrine effects _______ receptors
A and B
A
95
Bezold-Jarisch Reflex
stimulation of mechanoreceptors in the left ventricle causes bradycardia
96
What is the largest interlaminar space?
L5
97
What effect does neuraxial anesthesia have on the bowel?
Unopposed parasympathetic innervation:
Constriction
Increased peristalsis
98
Sympathetic innervation of the gut originates at
T5-L2
99
The cauda equina extends from ____ to \_\_\_\_\_\_
L1 to S5
100
To what degre will epinephrien extend the action of lidocaine?
Tetracaine?
Bupivicaine?
A little
A lot
hardly at all
101
In the supine position, the most dependent level of the spine is at
T4
102
What is normal CSF pressure?
10-20
103
Where are the two enlargements of the spinal cord?
Why?
cervical enlargement: C4 to T1 - Brachial Plexus
Lumbosacral: L2 to S3 - Lumbar and sacral plexus
104
When is a caudal epidural block frequently used?
Neonatal abdominal surgery
105
What is the preload crystalloid dose?
15ml/kg
106
The classic epidural test dose is
3ml, 15mg lidocaine
107
How can CSF be distinguished from saline?
Warm
+ for glucose
108
Which drugs are associated with increased incidence of POUR?
Opiods, anitcholinergics, sympathomimetics
109
When performing CSE, _______ should be used for loss of resistance while placing the epidural
Air
Prevents confusion of saline with CSF
110
A patient who received duramorph intraop develops pruritis, nausea, and ventilatory depression. What may be helpful?
Antiemetics
Narcan for ventilatory depression and pruritis
