Central Blocks Flashcards
(102 cards)
1
Q
label these guys
A
- epidural space
- ligamentum flavum
- cauda equina
- cona medullaris
- dura mater
- arachnoid mater
- pia mater
- spinal cord
2
Q
what connects the transverse process of a vertebra to the vertebral body?
A
pedicles
3
Q
what connects the transverse process of a vertebrae to the spinous process?
A
lamina
4
Q
where does the spinal cord terminate in most adults?
what is this called?
A
L1/L2 (depends on who you ask)
conus medullaris
5
Q
what does the spinal cord transition into once it ends?
A
collection of nerves called the cauda equina
6
Q
what is the importance of the cauda equina?
A
lessened risk of direct cord injury when a needle is placed into this space
7
Q
where is the epidural space located?
A
posterior to the dura and anterior to the ligamentum flavum
8
Q
contraindications to a central block (5)
A
- infection at the site of injection or near CNS
- coagulopathy or use of anticoagulants
- neuromuscular disease
- cardiac frailty
- patient consent & ability to tolerate procedure
9
Q
when placing an epidural, how do you know that the needle is passing through the ligamentum flavum and enters the epidural space?
A
a sudden loss of resistance to injection of air or saline
10
Q
how do you know that your spinal is in the correct place (subarachnoid space)?
A
freely flowing CSF
11
Q
what is the principal site of action for neuraxial blockade?
(M&M)
A
believed to be the nerve root, at least during initial onset of block
12
Q
what is the 1st ligament encountered when inserting the needle for a central block?
A
supraspinous ligament
13
Q
what is the most internal ligament that is immediately posterior to the epidural space?
A
ligamentum flavum
14
Q
2 approaches to place a central block
A
midline
paramedian
15
Q
why is the epidural considered a “potential space”?
A
it’s a collapsed structure like an uninflated balloon or esophagus
16
Q
what is contained in the epidural space?
A
nerves, vessels, and fat where roots pass outwardly
17
Q
if using the midline approach, how deep to the skin is the epidural space generally?
A
5 cm
18
Q
what borders the epidural space?
A
epidural veins
19
Q
why are central blocks contraindicated in a pt with MS?
A
effects of LA on cord
if necessary, epidural would be better than a spinal
20
Q
cardiac diseases that are absolute contraindications for central blocks
why?
A
outflow obstructions: aortic stenosis, HOCM, IHSS
SVR specific BP regulation, sympathectomy can result in cardiac arrest with difficulty resuscitating (TC said when they die they die 4real)
21
Q
what lab might you want to get in a pt on aspirin needing a central block?
A
TEG - tests platelet function
22
Q
ASRA recommendations for INR level prior to neuraxial block
(article)
A
“normal”
< 1.5
23
Q
s/s that warrant immediate evaluation after central block
A
- altered pain, temp, or motor function
- changes in bowel or bladder function
- severe back pain
24
Q
what is a “total” spinal?
A
injected meds block nerves high into the thoracic or even cervical levels
results in SNS blockade → bradycardia, hypotension, vascular collapse, apnea, LOC
25
interventions you should expect to do after you realized you just gave your pt a total spinal (oopsies)
manage airway
manage CV collapse (pressors, fluids)
26
adverse or exaggerated physiological responses assoc. with central blocks
(Table 45-6)
* urinary retention
* high block
* total spinal
* cardiac arrest
* anterior spinal artery syndrome
* Horner syndrome
27
what is Horner syndrome?
* unilateral sympathetic chain blockade
* more assoc. with peripheral blocks
* clinically looks like a stroke
* resolves when block wears off
28
complications of central blockade related to needle/catheter placement
(Table 45-6)
* backache
* dural puncture/leak - PDPH, diplopia, tinnitus
* neural injury
* bleeding
* misplacement (vascular injection, spinal, inadequate anesthesia)
* catheter shearing/retention
* inflammation
* infection
29
complications of central blocks r/t drug toxicity
(Table 45-6)
* systemic LA toxicity
* TNS
* cauda equina syndrome
30
what causes a PDPH ("spinal headache")?
what techniques can cause it?
dural puncture occurs and dural closure is inadequate, resulting in CSF leakage
large needle, multiple attempts
31
classic symptoms of a spinal headache (PDPH)
headache that's worse in upright position and relieved when supine
32
conservative treatment of spinal headache
rest, supine position, caffeine, hydration
33
management of a spinal headache if conservative measures fail
blood patch (20 mL blood used to “patch” dura)
should relieve within an hour or 2
34
why is a stylet used in a spinal block?
reduces likelihood of coring tissue during insertion
35
what is the purpose of non-cutting needles for spinal block?
cone-shaped tip designed to separate without cutting tissues
36
what is baricity?
* LA density relative to the density of CSF
* reflects the response of the injected LA to native CSF
37
isobaric solution
tends to stay in the same location
38
what is a hyperbaric solution?
* denser, heavier than CSF
* “sinks”
* tend to move to the most dependent area of the spine (T4-T8 in supine position)
39
what happens when a hyperbaric LA solution is injected and the pt is in a head-down position?
(book)
solution spreads cephalad
40
what happens when a hyperbaric solution is given and the patient is put in a lateral position?
(book)
greater effect on dependent (down) side
41
common additive to make a solution hyperbaric
7.5% dextrose
(typically pre-mixed as hyperbaric bupivacaine)
*of note, premixed hyperbaric bupivacaine has 8.25% dextrose in it*
42
what is a hypobaric solution?
* less dense (lighter) than CSF
* “floats”
43
if you give a hypobaric LA solution and put the pt in a head-down position, where is the solution going to go?
(book)
caudad
44
effect of a hypobaric solution move when pt is in a lateral position
(book)
greater effect on nondependent (up) side
45
when might you use a hypobaric spinal?
to affect the left hip while lying on the right
46
most important factors affecting the spread of spinal anesthesia
(table 45.2)
* baricity of solution
* position of patient during and immediately after injection
* drug dosage
* site of injection
47
“other” factors affecting dermatomal spread of spinal anesthesia
(table 45.2)
* age
* CSF
* curvature of spine/spinal stenosis
* drug volume
* intraabdominal pressure
* needle direction
* patient height
* pregnancy
48
advantages of using the midline approach over the paramedian approach
* fewer angles
* approach structures directly
* offers widest portion of epidural space
49
adverse effect of sympathetic blockade with central block
loss of vascular tone/SVR → hypotension
50
how quickly will you see “sympathectomy” with spinal block?
how can you prevent this?
within minutes of injection
small doses of pressors, volume challenge (in eligible pts)
51
what dermatome levels block cardioaccelerator nerves?
T1-T4
52
adverse effect of cardioaccelarator nerve blockade
* prominent, unopposed PNS stimulation (bradycardia)
* may have profound hypotension, LOC
53
adverse effect of neosynephrine for hypotension assoc. with sympathetic blockade
reflex bradycardia may result in asystole with a high-level spinal
54
most prominent cervical spinous process
C7
55
mL per dermatome initial dosing for lumbar epidural
(worksheet)
1-2 mL per segment (depending on pt height)
56
dermatome that corresponds with the base of the scapula
T7
57
dermatome that corresponds to the umbilicus
T10
58
dermatome level that corresponds with the superior aspect of the iliac crests
L4
59
how can blockade height be manipulated
by adjusting height and position at insertion
60
bupivacaine dosing to block perineum & lower limbs (via spinal)
(table 45-4)
4-10 mg
61
bupivacaine dose to block lower abdomen (via spinal)
(table 45-4)
is that what this means? sos
12-14 mg
62
bupivacaine dose to block upper abdomen (via spinal)
(table 45-4)
12-18 mg
63
how long does 0.75% bupivacaine in 8.25% dextrose last via spinal?
90-120 min
64
how long does 0.75% bupivacaine in 8.25% dextrose + epi last via spinal?
100-150 min
| (1.5-2.5 hrs)
65
advantages of epidural vs spinal?
* ability to create sensory blockade without motor blockade
* can titrate dosage to change spread and clinical effect
* can provide prolonged effect
* less dense motor block
66
disadvantages of epidural vs. spinal
larger needle placement =
* increased risk of bleeding from inadvertent vessel injury
* increased risk spinal headache if inadvertent subarachnoid puncture
67
disadvantages of epidural vs. spinal
larger needle placement =
* increased risk of bleeding from inadvertent vessel injury
* increased risk spinal headache if inadvertent subarachnoid puncture
68
how is clinical effect of an epidural acheived?
through both action on spinal roots as they pass through the epidural space and diffusion into CSF (where action is on spinal cord)
69
tell me about the needle used for an epidural catheter placement
special needle that's both blunted and curved
70
what is the purpose of a blunted curved needle for access to epidural space for catheter placement?
* blunting decreases likelihood of dural puncture
* curvature protects dura by avoiding a piercing tip on the distal end
71
2 techniques used to identify the epidural space
1. loss of resistance
2. hanging drop (using saline)
72
what should you do if attempting to place an epidural catheter and you realize you've punctured the dura?
remove the needle **and** the catheter (if placed already)
do not withdraw the catheter from the needle - if the catheter must be withdrawn, remove the needle then the catheter
73
test dose used for an epidural
3ml 1.5% lidocaine with 1:200,000 epi
(45 mg lidocaine, 15 mcg epi)
74
effect of a higher concentration agent with less volume
greater density with less spread
75
effect of a lower concentration agent with more volume
more diffuse but less intense blockade
76
mL needed to block T10 to S5
12 mL
77
does redosing of an epidural catheter require an additional test dose?
no, but should always be aspirated first
78
if you're trying to place an epidural but you lose resistance and see CSF when you remove the stylet, what should you do?
remove the needle, move up a level, try again :(
79
2% chloroprocaine:
onset?
sensory block?
motor block?
* onset - fast
* sensory - analgesic
* motor - mild to moderate
80
3% chloroprocaine:
onset?
sensory block?
motor block?
* onset: fast
* sensory: dense
* motor: dense
81
**≤** 1% lidocaine:
onset?
sensory block?
motor block?
* onset: intermediate
* sensory: analgesic
* motor: minimal
82
1.5% lidocaine:
onset?
sensory block?
motor block?
onset: intermediate
sensory: dense
motor: mild to moderate
83
2% lidocaine:
onset?
sensory block?
motor block?
* onset: intermediate
* sensory: dense
* motor: dense
84
1% mepivacaine:
onset?
sensory block?
motor block?
onset: intermediate
sensory: analgesic
motor: minimal
85
2-3% mepivacaine:
onset?
sensory block?
motor block?
* onset: intermediate
* sensory: dense
* motor: dense
86
**≤** 0.25% bupivacaine:
onset?
sensory block?
motor block?
* onset: slow
* sensory: analgesic
* motor: minimal
87
0.5% bupivacaine:
onset?
sensory block?
motor block?
* onset: slow
* sensory: dense
* motor: mild to moderate
88
0.75% bupivacaine:
onset?
sensory block?
motor block?
* onset: slow
* sensory: dense
* motor: moderate to dense
89
0.2% ropivacaine:
onset?
sensory block?
motor block?
* onset: slow
* sensory: analgesic
* motor: minimal
90
0.5% ropivacaine:
onset?
sensory block?
motor block?
* onset: slow
* sensory: dense
* motor: mild to moderate
91
0.75% - 1% ropivacaine:
onset?
sensory block?
motor block?
* onset: slow
* sensory: dense
* motor: moderate to dense
92
if you're trying to remove an epidural catheter and it won't come out (yikes) what should you do?
put pt in placement position - may open spaces sufficiently to withdraw the catheter
93
concentration of epidural lidocaine for sensory block
motor/surgical block?
* sensory: ≤ 1%
* motor: 2%
94
concentration of epidural bupivacaine for a sensory vs. motor/surgical block
* sensory: ≤ 0.25%
* motor: 0.5%
\*if he tries to get tricky, 0.75% best for motor but apparently unavailable
95
concentration of epidural ropivacaine for a **sensory** block
0.2%
96
concentration of chloroprocaine for a **motor**/surgical block
3%
97
1. C5
2. T10
3. L2
4. L3
5. L5
98
A. C6
B. C7
C. C8
D. T1
E. T2
99
A. C5
B. C6
C. S2
D. S1
100
0.5% ropivacaine:
onset?
sensory block?
motor block?
* onset: slow
* sensory: dense
* motor: mild to moderate
101
Which neuraxial dose **of opioids** is similar to IV dosing?
Epidural
102
Subarachnoid dosing of opoids is about \_\_\_\_\_\_% of IV dosing
10-20%
