Neuraxial Anesthesia: A Review Flashcards
1
Q
which interspace is tuffiers line
A
L4-L5
2
Q
where does the spinal cord end
A
L1/L2
3
Q
what is the target for the spinal and the epidural
A
nerve roots
4
Q
anatomical considerations for the parturient
A
engorged epidural veins, makes dura small and creates exaggerated spread during spinal administration
5
Q
what is the solution mixed with an epidural always
A
normal saline
6
Q
spinal: what does it depend on (4 most important factors)
A
dosage, baricity, patient positioning, site of injection
7
Q
what kind of block is an epidural/what does it depend on?
A
the volume of LA which determines the dermatome level
8
Q
absolute contraindications to neuraxial anesthesia
A
patient refusal increased ICP severe aortic or mitral valve stenosis * coagulopathy or bleeding diathesis severe hypovolemia infection at injection site
9
Q
aortic valve stenosis: mild. jet velocity (m/sec), mean gradient (mmHg), valve area (cm^2)
A
jet velocity (m/sec) <3 mean gradient (mmHg) <25 valve area (cm^2) >1.5
10
Q
aortic valve stenosis: moderate. jet velocity (m/sec), mean gradient (mmHg), valve area (cm^2)
A
jet velocity (m/sec) 3-4 mean gradient (mmHg) 25-50 valve area (cm^2) 1-1.5
11
Q
aortic valve stenosis: severe. jet velocity (m/sec), mean gradient (mmHg), valve area (cm^2)
A
jet velocity (m/sec) >4 mean gradient (mmHg) >50 valve area (cm^2) <1
12
Q
aortic valve stenosis: critical. jet velocity (m/sec), mean gradient (mmHg), valve area (cm^2)
A
jet velocity (m/sec) >5 mean gradient (mmHg) >80 valve area (cm^2) < .7
13
Q
relative contraindications to neuraxial anesthesia (7)
A
uncooperative patient LA allergy (esters >amide) patient on anticoagulant or thrombolytic therapy preexisting neurologic deficit chronic headache or backache severe spinal deformity valvular stenosis
14
Q
informed consent: document the following
A
advantages and disadvantages
block appropriate for procedure but not guaranteed
risks and benefits
ensure patient understands
allow patient to ask questions
do not attempt to dissuade from general if already agreed to
15
Q
consider having these two things started before spinal administration
A
bolus and phenylephrine infusion
16
Q
at minimum, monitor these things during neuraxial administration
A
peripheral IV patency suction airway sypplies EKG, BP, pulse ox, possibly O2 supportive meds (induction agent, paralytic, atropine, vasoactive medication)
17
Q
how to create larger interspinous spaces
A
aside from angry cat or shrimp position, have them push against your thumb
18
Q
prior to starting procedure, verify
A
patent IV
monitoring devices, oxygen attached and functioning
resuscitation equipment available
19
Q
what is the most commonly used interspace for a spinal
A
L3-L4
20
Q
describe a touhy needle used for epidurals
A
pronounced curve
blunt tip
easier for novices
directional placement of catheter
21
Q
describe a crawford needle used for epidurals
A
not curved
easier to insert
higher rate of dural punctures
22
Q
for an epidural, distance to ligamentum flavum varies with
A
body habitus
level of plcement
23
Q
standard depth of ligamentum flavum
A
4-6cm
24
Q
does an epidural needle require an introducer
A
no, theyre larger more rigid needles
25
describe the bromage grip for epidural placement
hand firm support to stabilize needle
attach and secure syringe
passing catheter through needle
26
name ligaments in order to dura
```
supraspinous
interspinous
ligamentum flavum
epidural space
dura
```
27
what happens if you see a small amount of clear fluid during epidural placement
CSF would be a copious amount, so a small amount is ok
28
how many gauges smaller than the epidural needle is the epidural catheter
typically two gauges smaller than a needle
29
what happens if paresthesias occur during catheter placement
stop. if it isn't persistent, its ok to keep going. theyre not uncommon
30
how far do you advance the epidural catheter
3-5cm past the needle hub
31
shallow placement of epidural catheter may result in
dislodgment of epidural space
32
too deep placement of epidural catheter may result in
puncture of dura
passage into epidural vein
migration through intervertebral foamen
33
test dose for epidural?
first, aspirate
1.5% lidocaine and 1:200,000 epinephrine
inject 3mL which is 45mg lidocaine and 15mcg epinephrine
34
if needle is in intravascular space during epidural test dose, what do you anticipate seeing
increase in HR and BP
35
what is in hyperbaric solution for a spinal
dextrose
36
what is in hypobaric solution for a spinal
sterile water
37
other factors related to spinal level (not the most important 4) include
```
patient height
pregnancy
age
CSF volume
curvature of the spine
volume
intra abdominal pressure
needle direction
```
38
what is the most dependent area of the spine that hyperbaric solutions mitigate to
T4-T8
39
spinal needles that are not cutting needles (3)
whitacre, sprotte, pencan
40
how to utilize a cutting needle to minimize frequency of PDPH
rotate it 90 degrees, separates dura a little more and cuts a little less
41
what are the two pops felt during a spinal
ligamentum flavum
| dura
42
how to do a continuous spinal (and why)
provides prolonged surgical anesthesia and postoperative pain management
dura punctured 17 gauge epidural needle
epidural catheter passed through dura than subarachnoid space
43
when to consider a continuous spinal
consider when a wet tap occurs during epidural placement
44
describe a two level CSE
spinal placed first
| epidural catheter placed 1-2 levels above
45
describe a one level CSE
placement of epidural needle
spinal needle passed through
small intrathecal dose injected (opioid or smaller dose of LA)
epidural catheter placed
46
goal of CSE
relieve pain so mom can deliver
47
additional concerns of CSE include (3)
intrathecal opioid effects on fetus
inability to ambulate after receiving narcotics
maternal hypotension and itching
48
potential complications of CSE include (6)
```
failure to obtain either intrathecal or epidural block
catheter migration
increased spinal level
metallic particles
PDPH
neurologic injury
```
49
if you use the paramedian approach for a spinal, which ligaments do you not go through
the supraspinous and interspinous ligament
50
if youre hitting bone early during insertion of spinal,
you are touching the superior crest of spinous process below the interspace. redirect cephalad
51
if youre hitting bone late during insertion of a spinal,
needle is touching the inferior surface of the spinous process above the interspace. redirect caudal
52
if paresthesia does not resolve during insertion of spinal
remove and reposition
53
if you get frank blood during insertion of a spinal, you are likely in
an epidural vein. withdrawal and reposition
54
if you get blood tinged CSF during placement of a spinal,
allow CSF to flow for several seconds. when clear, inject medication
55
does LA metabolize in CSF
no, this is based on rate of absorption into systemic vasculature.
56
what will addition of vasoconstrictors to neuraxial anesthesia do
slow absorption and prolong block
57
esters include (3)
procaine, chlorprocaine, tetracaine
58
amides include (4)
lidocaine, mepivicaine, ropivicaine, bupivicaine
59
procaine: pKa, percent ionized, percent protein binding, onset, DOA
```
pKa 8.9
percent ionized 97
percent protein binding 6
onset slow
DOA 60-90 minutes
```
60
chlorprocaine onset, DOA
onset fast
| DOA 30-60 minutes
61
tetracaine pKa, percent ionized, percent protein binding, onset, DOA
```
pKa 8.5
percent ionized 93
percent protein binding 94
onset slow
DOA 180-600
```
62
lidocaine pKa, percent ionized, percent protein binding, onset, DOA
```
pKa 7.9
percent ionized 76
percent protein binding 64
onset fast
DOA 90-120
```
63
mepivicaine onset, DOA
fast, 120-240
64
ropivicaine onset, DOA
slow, 180-600
65
bupivicaine pKa, percent ionized, percent protein binding, onset, DOA
```
pKa 8.1
percent ionized 83
percent protein binding 95
onset slow
DOA 180-600
```
66
neuraxial additives: epinephrine
MOA
dose
greater effect with
alpha 1 agonist
.1-.2mL of 1:1000 solution can be added to LA's
greater effect with tetracaine
67
neuraxial additives: phenylephrine MOA, dose, greatest effect with?
pure alpha agonist slightly more effective than epinephrine
.05-.2mL of 1% solution (.5-2mcg added to LA)
greatest effect with tetracaine
68
```
neuraxial additives: clonidine
MOA
contraindicated with?
synergistic with
helps with
```
selective alpha 2 agonist
used when epinephrine is contraindicated
when mixed with lidocaine or bupivicaine, has synergistic effects
the central action appears to help with tourniquet pain
69
most common neuraxial additives include
fentanyl
| morphine
70
fentanyl as a spinal additive: solubility
high lipid solubility. binds directly to lipid elements of spinal cord. less drug available to diffuse systemically.
71
fentanyl as a spinal additive: dosage, onset, DOA
provides profound analgesia
12.5-25mcg mixed with LA
onset: 5-10 minutes
DOA: 2-4 hours
72
morphine as a neuraxial additive (spinal OR epidural): solubility
highly polarized, not very lipid soluble
drifts freely in CSF
in approx 6-8 hours, will rise to respiratory center
73
morphine as a neuraxial additive (spinal OR epidural): dosage, onset, DOA
provides profound analgesia
.1-.25mg mixed with LA
onset 60-90 minutes
DOA approx 24h
74
morphine as a neuraxial additive (spinal OR epidural): adverse effects (3)
itching
urinary retention
delayed respiratory depression
75
dexmedetomidine as a neuraxial additive: dosing
spinal: 5mcg
epidural: 20-50mcg
76
dexmedetomidine as a neuraxial additive: side effects
```
profound hypotension (when used in conjunction with an opioid ex: precedex and fentanyl)
prolonged block
```
77
which fibers are blocked first for neuraxial anesthesia
sympathectomy: 1st, preganglionic B fibers. vasodilation=good block aka drop in BP first sign. n/v may follow
78
fiber type: A alpha
| function, diameter, myelination, block onset
proprioception
6-22
heavy
last
79
fiber type: A beta
| function, diameter, myelination, block onset
touch, pressure
6-22micrometers
heavy
intermediate
80
fiber type: A gamma
| function, diameter, myelination, block onset
muscle tone
3-6
heavy
intermediate
81
fiber type: A delta
| function, diameter, myelination, block onset
pain, cold, temperature, touch
1-5
heavy
intermediate
82
fiber type: B
| function, diameter, myelination, block onset
preganglionic autonomic vasomotor
<3
light myelination
early block onset
83
fiber type: C sympathetic
| function, diameter, myelination, block onset
postganglionic vasomotor
.3-1.3
no myelination
early onset
84
fiber type: C dorsal root
| function, diameter, myelination, block onset
pain, warm and cold temperature, touch
.4-1.2
no myelination
early block onset
85
which fibers follow B fibers and what is the result
a delta and C pain fibers and temperature follow B fibers.
unable to discriminate light touch or temeprature
temperature discrimination mirrors sensory loss
86
which are the last fibers to be blocked and what is the result
A alpha beta and gamma
| touch and proprioception, surgical muscle relaxation, may feel pressure
87
what are the goal nerve fibers for a labor epidural
a delta and C fibers so she can still feel contractions
88
evaluation of block
assess block q2-3 minutes
frequent assessment of BP and VS
physiologic changes closely resemble block level
89
which dermatome level do you need for labor analgesia
T10
90
which dermatome level do you need for a C section
T4-T6
91
autonomic blockade is where in relation to sensory block? motor blockade is where in relation to sensory block?
autonomic blockade is usually two dermatomes higher than the sensory block
motor blockade is usually two dermatomes lower than the sensory block
92
complications to neuraxial anesthesia
```
HoTN
intercostal muscle paralysis
apnea/phrenic nerve paralysis
paresthesia
subarachnoid or epidural hematoma
meningitis/epidural abscess
chemical meningitis
n/v
PDPH
```
93
what may a patient complain about when having a PDPH
if i lay down i feel fine, if i sit up I have a HA
94
risk factors for PDPH include
```
patient needle size and type
patient population (young, female, pregnancy)
```
95
s/sx of PDPH
```
bilateral frontal or rtetroorbital or occipital
extends into next
photophobia
nausea
positional
```
96
PDPH treatment in first 12-24 hours (conservative)
```
recumbent position
analgesics
fluid administation
caffeine
stool softeners and soft diet
```
97
epidural blood patch for PDPH includes
injecting 15-20mL autologous blood
below initial puncture site by 1-2 levels
90% will respond to initial therapy
