Neuraxial anesthesia II Flashcards
(103 cards)
1
Q
what is the controversial connective tissue between the ligamentum flavum and dura mater?
A
plica mediana dorsalis
*not definitively confirmed
2
Q
what is the clinical relevance of the plica mediana dorsalis?
A
possible reason for unilateral blockade in epidural anesthesia
(epidural is laterally placed, not midline)
3
Q
where is the subarachnoid space? what does it contain?
A
- space between the arachnoid mater and pia mater
- contains CSF, spinal cord, and nerve roots
- primary target for spinal anesthesia
4
Q
how do we know we are in the subrachnoid space when performing spinal anesthesia?
A
characteristic “pop” is fet when passing through dura mater
5
Q
which meningeal layer is delicate and highly vascular that should not be punctured during spinal anesthesia?
A
pia mater
directly attached to the spinal cord
6
Q
what is the protective layer between the dura mater and pia mater?
A
arachnoid mater
thin connective tissue
7
Q
what is the tough fibrous shield that protects the spinal cord and is the first layer encountered during spinal anestesia?
A
dura mater
8
Q
where does the dura mater begin and end?
A
foramen magnum to dural sac
9
Q
how many total pairs of spinal nerves are there?
A
31 pairs
10
Q
how many cervical nerves?
A
8 pairs
11
Q
which spinal nerve is unique in that it exits below the vertebra?
A
C8 nerve
exits below C7 (the rest exit above the vertebra)
12
Q
how many thoracic nerves?
A
12 pairs
13
Q
how many lumbar nerves?
A
5 pairs
14
Q
how many sacral nerves?
A
5 pairs
15
Q
how many coccyx nerves?
A
1 pair
16
Q
each nerve has how many roots?
A
- Each nerve is formed by the joining of two different nerve roots
- anterior root
- posterior root
17
Q
what info does the anterior root relay? what about the posterior root?
A
- anterior = motor and autonomic
- posterior = sensory
18
Q
what is a dermatome?
A
area of skin that receives sensory nerves from a single spinal nerve root
19
Q
which spinal nerve innervates the lower limbs?
A
L1, L2, L3, L4
20
Q
which spinal nerve innervates the feet?
A
L4, L5, S1
21
Q
which spinal nerve innervates the perineum?
A
S2, S3, S4
22
Q
which spinal nerve innervates the umbilicus?
A
T10
23
Q
which spinal nerve innervates the hands?
A
C6, C7, C8
24
Q
which spinal nerve innervates the nipples?
A
T4
w
25
which spinal nerve innervates the face?
* trick question - it is not innervated by spinal nerves
* CN V (Trigeminal nerve: V1, V2, V3)
26
what are the branches of the trigeminal nerve CN V?
V1 = opthalmic
V2 = maxillary
V3 = mandibular
27
what are different names for spinal anesthesia?
intrathecal anesthesia
subarachnoid block
28
what is a saddle block?
* block for peri-anal surgery
* S2-S5
29
What surgeries require L1 block? how about L2?
L1 = thigh, lower leg, knee
L2 = foot/ankle
30
what surgeries can be done with a T10 block?
* vaginal delivery
* uterus
* hip
* tourniquet?
* TURP
31
what is the level of block for penile vs scrotal surgery?
Penis = S2
Scrotum = S3
32
what is the level of block for cesarean or upper abdominal surgery?
T4 (cardiac accelerator region-must have emergency drugs)
33
what is the level of block for urologic/gynecologic or lower abdominal surgery?
T6
34
what is the level of block for testicular (not scrotum) surgery?
T8
*scrotum is S3
35
what are the **controllable** factors that affect spread in spinal anesthesia?
* baricity
* position
* dose
* site of injection
36
what are the **non-controllable** factors that affect spread in spinal anesthesia?
* Volume of CSF
* Increased Intra-abdominal Pressure (obesity,pregnancy)
* Age (elderly)
37
what **does not** affect spread in spinal anesthesia?
* Barbotage (repeated aspiration and reinjection of CSF)
* Speed of Injection
* Orientation of Bevel
* Addition of Vasoconstrictor
* Gender
38
what has the biggest impact on spread in spinals?
**dose**
*for isobaric and hypobaric LAs
39
what has the biggest impact on spread in spinals using hyperbaric LAs?
**baricity**
40
how does CSF volume affect spread of spinal anesthesia?
low CSF = more spread
41
what 2 factors cause decreased CSF volume?
* old age
* pregnancy (due to increased IAP)
42
**controllable** factors that greatly affect spread in **epidural** anesthesia?
* Local Anesthetic Volume (Most important drug related factor)
* Level of injection (Most important procedure related factor)
* Local Anesthetic dose
43
**non-controllable** factors that greatly affect spread in **epidural** anesthesia?
* Pregnancy
* Old Age
44
smaller effect on spread, controllable factors for epidural anesthesia?
* Local Anesthetic Concentration
* Patient Position
45
smaller effect on spread, non-controllable factors for epidural anesthesia?
height
*may still affect spread but only slightly
46
what does not affect spread for epidurals?
* Additives in the Anesthetic
* Direction of the Bevel of the Needle
* Speed of Injection
47
lumbar epidural mostly spreads?
cephalad (Up)
48
mid-thoracic epidural mostly spreads?
balance between cephalad and caudad
49
cervical epidural mostly spreads?
caudad (down)
50
what nerve fiber is blocked first? what is its function?
* **preganglionic B fibers**
* autonomic (SNS)
51
what nerve is blocked second? function?
* **unmyelinated C fibers**
* sensory
52
what are the third nerves to be blocked? what is their function?
* **A-delta**
* sensory/motor
* medium myelination
53
last nerves to be blocked? function?
* **A-alpha**
* **A-beta**
* **A-gamma**
* motor function
* highly myelinated
54
what is selective inhibition of specific nerve fibers within a mixed nerve by LAs, based on factors like nerve fiber size, myelination, and function?
* **Differential blockade**
* different nerve fibers are blocked at different times
55
what is the order of blockade based on nerve fiber type?
1. B-fiber
2. C-fiber
3. A-delta fiber
4. A-gamma, A-beta, A-alpha
56
B-fibers are primarily responsible for?
autonomic SNS
57
which nerve fibers are responsible for pain and temp sensation?
* C-fibers
* A-delta fibers
58
fiber responsible for motor tone?
A-gamma
59
fiber responsible for touch and pressure?
A-beta
60
fiber responsible for motor and proprioception?
A-alpha
61
If sensory blockade is at T5, what level is SNS? motor?
SNS = C6-T3 (2-6 levels above)
motor = T7 (2 levels below)
62
which nerve fiber is blocked the longest?
**preganglionic B fibers**
blocked first and recovers last
63
what is the order of sensory blockade for the following: Pain, touch, temp?
* Temperature
* pain
* touch and pressure
64
what is the modified bromage scale?
* measures scale of motor blockade
* 0: No motor block.
* 1: Slight motor block. The patient cannot raise an extended leg but can still move the knees and feet.
* 2: Moderate motor block. The patient cannot raise an extended leg or move the knee but can move the feet.
* 3: Complete motor block. The patient cannot move the legs, knees, or feet
65
what type of motor movement does the modified bromage scale evaluate?
evaluates **lumbosacral nerves** ONLY
only assess movement below this level (i.e. not upper extremities)
66
what are the CV effects of neuraxials?
decreases everything:
decreased **preload** - systemic venodilation
decreased **afterload** - systemic arterial dilation
decreased **CO** - increased initially*
decreased **HR** - blockade of cardiac accelerator fibers
67
what percent is **afterload** reduced in healthy vs diseased patients receiving neuraxials?
healthy patients = 15%
diseased = 25%
68
what is the Bezold-Jarisch Reflex?
* CV reflex involving significant **bradycardia** and **asystole**
* triggered by neuraxial
* mediated by **5-HT3 receptors** in the **vagus nerve** and **ventricular myocardium**
69
what is the bainbridge reflex?
increase in venous return stretches the right atrium
triggering receptors that signal the medulla oblongata to increase heart rate
70
what is reverse bainbridge reflex?
reduced venous return in the heart leads to reduced stretch of the right atrium
signals medulla oblongata to reduce HR
71
what happens to parasympathetic stimulation during neuraxial at T4 and above?
* neuraxial at T4 and above blocks cardiac accelerators
* parasympathetic system becomes unopposed by cardiac accelerator
* leads to uncontrolled parasympathetic tone and sudden cardiac arrest
72
what is the incidence of sudden cardiac arrest in young adults for **epidurals**?
1:10,000
73
what is the incidence of sudden cardiac arrest in young adults for **spinals**?
7:10,000
74
when does sudden cardiac arrest occur most often after onset of spinal?
20-60 mins
75
sudden cardiac arrest is most often associated with what 2 conditions?
* large blood loss
* orthopedic cement placement
76
how can spinal-induced hypotension be prevented?
* vasopressors (phenylephrine, ephedrine)
* 5-HT3 antagonist (ondansetron) for Bezold-Jarisch reflex
* fluid management (co-loading vs preloading)
* positioning (slight pelvic tilt)
77
what is co-loading vs preloading in terms of fluid management?
co-loading = 15 ml/kg after spinal (preferred)
preloading = IVF before spinal (avoid)
78
what respiratory accessory muscles are affected with high thoracic blockade?
intercostals
abdominal muscles
decreased forced expiration capacity
79
neuraxial anesthesia should be used with caution in patients with? (2)
COPD
Pickwickian syndrome (obesity hypoventilation syndrome)
80
what is an extremely common respiratory complication with neuraxials? why?
**dyspnea**
loss of sensory feedback from chest area
loss of ability for deep breath and cough
81
what lung volume is decreased with neuraxials?
ERV
82
apnea from neuraxial is rare, but if it occurs what could be the cause?
decreased blood flow to the brainstem
83
what does the GI parasympathetic AFFERENT branch do?
* satiety
* distension
* nausea
84
what does the GI parasympathetic EFFERENT branch do?
* tonic contractions
* sphincter relaxation
* peristalsis
* secretion
85
what does the GI sympathetic AFFERENT branch do?
visceral pain
86
what does the GI sympathetic EFFERENT branch do?
* inhibit peristalsis and gastric secretion
* causes sphincter contraction and vasoconstriction
87
GI parasympathetic stimulation is primarily through which nerve?
vagus nerve (originates in medulla)
88
sympathetic innervation of GI tract stems from which vertebra?
T5-L2
89
how does neuraxial anesthesia affect the GI system?
* reduced sympathetic tone
* increased parasympathetic activity
* unopposed vagal tone (rest and digest)
90
T/F: renal blood flow is severely decreased with neuraxials
False
no change in renal blood flow when MAP is maintained
91
sympathetic blockade above ____ affects bladder control
T10
urinary sphincter relaxes
92
addition of what drug to neuraxials worsen urinary retention?
* **opioids**
* decreased detrusor contraction
* increased bladder capacity
* need foley catheter
93
what are the metabolic/neuroendocrine effects of neuraxial anesthesia?
reduced cortisol, epinephrine, norepinephrine, vasopressin release
reduced RAAS activation
(pain, inflammation, tissue trauma increases these)
94
what are the chemical components of LAs?
aromatic ring = lipophilic head
intermediate chain = determines class
tertiary amine = hydrophilic tail
95
what is the chemical formula for esters? amides?
ester = -COO
amide = -NHCO
96
what determines the onset of action?
pKa
97
what determines potency?
lipid solubility
98
what determines duration of action?
protein binding
99
what are the esters?
* benzocaine
* cocaine
* chloroprocaine
* procaine
* tetracaine
100
what are the amides?
* bupivicaine
* dibucaine
* lidocaine
* mepivacaine
* ropivacaine
101
which class of LAs do allergic reactions commonly occur? why?
**esters**
PABA metabolite
102
why is amide allergic reaction rare?
contains methylparaben preservative
103
what is the order of vascular uptake from most to least?
* intravascular
* tracheal
* intercostal
* caudal
* paracervical
* brachial
* sciatic
* subcutaneous
