Spinal & Epidural Lecture 3 Flashcards
(121 cards)
1
Q
What does baricity refer to?
A
Density of local anesthetic solution compared to the CSF
2
Q
What is the density of an isobaric local anesthetic? How does this affect the behavior?
A
- LA density is equal to CSF density
- Isobaric solution baricity of 1= density matches CSF
- Tends to stay in place where its injected
3
Q
What is the density of a hyperbaric LA? What is the behavior?
A
- Density is greater than CSF
- Baricity is greater than 1
- Sinks in CSF and moves downward from injection point
4
Q
What is the density of a hypobaric LA? what is the behavior in CSF?
A
- Density is less than CSF
- Baricity less than 1
- Rises in CSF and moves upward from point of injection
5
Q
What type of LA baricity do you want if you are wanting the block to travel higher?
A
Usually want LA that will sink (hyperbaric) because we can manipulate OR table to move LA up
6
Q
Which local anesthetics are hyperbaric?
A
- Bupivacaine 0.75% in 8.25% dextrose
- Lidocaine 5% in 7.5% dextrose
- Tetracaine 0.5% in 5% dextrose
- Procaine 10% in water
7
Q
Which LAs are isobaric?
A
- Bupivacaine 0.5% in saline
- Bupivacaine 0.75% in saline
- Lidocaine 2% in saline
- Tetracaine 0.5% in saline
8
Q
Which LAs are hypobaric?
A
- Bupivacaine 0.3% in water
- Lidocaine 0.5% in water
- Tetracaine 0.2% in water
9
Q
How does the spread of LA occur from the site of injection?
A
Cephalad and caudad direction from site of injection
10
Q
What does spinal cord reuptake of LA from the pia mater depend on?
A
Lipid soluble nature
11
Q
What is the lowest point and highest point for SAB with hyperbaric LA when the patient is placed supine?
A
High point: T6
Low point: S2
12
Q
What is the lowest point and highest point for SAB with hypobaric LA when the patient is placed supine?
A
High point: C3
Low point: L3
13
Q
How are all neuraxial local anesthetics eliminated?
A
Vascular reabsorption (vessels in pia mater)
No metabolism in CSF
14
Q
__________ drugs have slow reuptake because they have high affinity for epidural fat
A
Lipophilic
Bupivacaine longer duration than lidocaine
15
Q
Which spinal drugs can have epi additive to increase duration of block?
A
- Bupivacaine 0.5-0.75%
- Tetracaine 0.5-1%
16
Q
How much does the addition of epi to spinal anesthetics increase the duration of action?
A
20-50% increase in duration of action
17
Q
How many mL of 0.75% Bupivacaine would you give if giving 15mg?
A
2mL (7.5mg/mL)
18
Q
What are common LA used for intrathecal (SAB) anesthesia?
A
- Bupivacaine 0.5 - 0.75%
- Levobupivacaine 0.5%
- Ropivacaine 0.5- 1%
- 2-Chloroprocaine 3%
- Tetracaine 0.5-1%
19
Q
What dose of bupivacaine intrathecal would you use to block up to T10? What dose to block up to T4?
A
T10 block: 10-15 mg
T4 block: 12-20 mg
20
Q
What dose of intrathecal Levobupivacaine 0.5% would you give to block up to T10? What dose to block up to T4?
A
T10: 10-15 mg
T4: 12-20 mg
21
Q
Dose of spinal Ropivacaine to block up to T10:
Dose to block up to T4:
A
T10: 12-18mg
T4: 18-25 mg
22
Q
What is the dose of 2-Chloroprocaine 3% for SAB up to T10? Dose to block up to T4?
A
T10: 30-40 mg
T4: 40-60 mg
23
Q
What is the dose of Tetracaine for SAB to block up to T10? What dose to block T4?
A
T10: 6-10 mg
T4: 12-16 mg
24
Q
What is the purpose of incremental dosing with 5mL for epidurals?
A
- Avoid high spinal
- Avoid hypotension from rapid autonomic block
- Avoid local anesthetic toxicity
25
Why is epi used in epidural test dose?
If HR increases and pt has impending doom/feeling like they are going to pas out→ epi was injected systemically in vein (need to adjust catheter placement)
26
What is the next step once you have loss of resistance and are in the epidural space?
Common to inject 10cc NS to open up epidural space before placing catheter and injecting LA (provider preference)
27
What is the onset of epidural blocks?
10-25 min
28
When should you redose epidural?
When sensory block is regressing by 2 segments → top off epidural to increase back to desired block level
29
What is the fastest onset/shortest acting neuraxial local anesthetic?
2-Chloroprocaine→ super basic pKa but high concentration
30
When is 2-chloroprocaine commonly used?
OB→ second to lidocaine for epidurals
31
How is 2-chloroprocaine metabolised?
Plasma cholinesterase = short lived (redose every 45 min)
32
What class of LA is 2-chloroprocaine?
Ester
33
What can be added to LA to speed onset of epidural?
Sodium bicarb (1mEq/ 10mL LA) → increases pH of LA therefore increases onset of action
34
How dose alkalization of LA with NaHCO3 affect epidural?
- Increases concentration of nonionized free base
- Increases rate of diffusion of drug
- Increases speed of onset of block
*Not super common in practice but common test q*
35
What is the typical dose for epdiural top-up dose to maintain block at desired level?
50% -75% of initial dose
36
When are top-up epidural doses adminstered?
Before the block decreases more than 2 dermatomes
37
How does the epidural space differ from thoracic to lumbar regions?
Smaller epidural space in thoracic regions compared to lumbar → greater spread in thoracic
38
The _________of the LA affects how dense or strong the epidural block is
Concentration
39
How is a "walking epidural" achieved?
Using a low concentration of LA that manages pain but allows some motor function
40
If your initial epidural dose was 6mL lidocaine and the patient now has sensation 2 levels below intended block level, how much additional lidocaine should you give?
3mL (50-75% initial dose)
41
What is the purpose for most neuraxial adjuncts?
Postop pain management by extending LA effect to post op
42
What are common opioids used with neuraxial?
- Sufentanil
- Fentanyl
- Morphine
43
How does the addition of opioids to neuraxial impact the block?
- No extension of duration
- Improves analgesia
- Improves density of block
44
How does addition of alpha 2 agonists to neuraxial anesthesia impact the block?
- Improves density of block
- Increases duration
- Improves analgesia
45
What route can precedex be given to improve density, duration, and analgesia of neuraxial anesthesia?
IV or intrathecal (intrathecal not yet FDA approved→ a few studies show neuro complications
46
What effect does addition of vasopressor have on neuraxial anesthesia?
Extends duration (no effect of analgesia or density of block)
47
What is the target for neuraxial opioids?
- Substantia gelatinosa of dorsal horn (lamina 2)
- Neurotransmission is reduced by decreasing cAMP, decreased Ca2+ conductance, and increased K+ conductance
- Neuraxial opioids also diffuse into general circulation and affect opioid receptors throughout the body (broad pain relief)
48
Hydrophilic neuraxial opioids:
- Morphine
- Hydromorphone
- Meperidine
49
Lipophilic neuraxial opioids:
- Fentanyl
- Sufentanil
50
What are the properties of hydrophilic neuraxial opioids?
- Stays longer in CSF
- Spread widely and more rostral
- Takes longer to start working (30-60 min)
- Lasts longer (6-24 hrs)
- Less systemic absorption
- Late respiratory depression
*pain control lasts longer*
51
What are the properties of lipophilic neuraxial opioids?
- Less time in CSF
- Limited spread and less rostral
- Starts working quickly (5-10 min)
- Shorter effect (2-4 hrs)
- More systemic absorption
- Resp depression happens earlier (would see in OR)
52
What is the drugs movement like for intrathecal administration of opioids?
Opioid quickly diffuses into spinal cord→ more direct and immediate effect of pain because its closer to nerve roots
53
What is the drugs movement like for epidural administration of opioids?
- Opioid diffuses through fatty tissue in epidural space then slowly crosses into dural cuff and into CSF to reach spinal cord (some of the drug enters blood stream by diffusing through vessels in epidural space)
54
How does opioid dose for epidural compare to spinal?
Need higher opioid dose for epidural because only a portion of the drug reaches the target area in the spinal cord
55
If a patient is having outpatient surgery and it getting intrathecal morphine, what dose should you use?
Lower dose so pt will be safe to DC (0.25 mg)
56
What is the most common side effect of neuraxial opioid administration?
Pruritis
57
What is the treatment for pruritis from neuraxial opioids?
- Benadryl 25-50mg IV
- Naloxone 0.1mg (last resort but works the best)
- Buprenex (mixed agonist/antag)
58
What can be done prophylactically to minimize itching from neuraxial opioids?
- Minimize morphine dose (<300mcg)
- Ondansetron 4mg IV
- Nubain 2.5-5 mg IV (usually give in OR)
59
What monitors does intrathecal morphine require?
- Capnography
- Pulse ox
- Alarms
*Apnea monitoring*
60
Which intrathecal opioid has the highest incidence of respiratory depression?
Morphine (hydrophilic nature causes cephalad spread)
61
How is respiratory depression from intrathecal morphine treated?
Naloxone 0.1-0.2 mg
62
How can nausea and urinary retention for opioids be avoided?
- Dose dependent (Lower doses better) → <100mcg morphine PONV almost absent
- Decide dose based on preop assessment and risk factors
63
What are some treatment options for PONV from neuraxial opioids?
- Ondansetron (5HT antag)
- Naloxone 0.1mg
- Phenergan 12.5- 25mg IM
64
What is the incidence of urinary retention post spinal opioid?
30-40%
65
How long can Clonidine and precedex can prolong sensory and motor blockade?
1 hour
*common to have hypotension, bradycardia, and sedation S/E*
66
What is the dose for spinal and epidural precedex?
3mcg
67
What is the dose for spinal and epidural clonidine?
15-45 mcg
68
What is the dose of neuraxial epi to prolong duration?
0.2-0.3mg "epi wash"
69
What is the neuraxial dose of phenylephrine to prolong action of block?
2-5mg
70
What happens to block duration when epi wash is added to tetracaine vs lidocaine and bupivacaine?
PROFOUND increase in block duration with tetracaine + epi compared to variable increase in duration with lidocaine and bupivacaine
71
What are symptoms of epidural hematoma?
- Lower extremity weakness/numbness
- Low back pain
- Bowel and bladder dysfunction
72
What is the treatment for epidural hematoma?
Surgical decompression within 8 hours to optimize recovery chances
73
When do you hold aspirin for neuraxial anesthesia?
- High risk and intermediate risk procedures→ Hold aspirin 4-6 days
- Low risk procedures→ continue aspirin
74
How long to hold NSAIDs for high risk procedures?
5 half lives
75
Do we need to hold NSAIDs for intermediate and low risk surgeries?
- Intermediate risk procedures: hold NSAIDS for cervical ESI and stellate ganglion block
- Low risk procedures: do not need to hold
76
How long to hold Triofiban and Eptifibatide?
4-8 hours (and plt function recovered)
77
How long to hold Abciximab?
24-48 hours (and plt function recovered)
78
How long to hold plavix before neuraxial?
5-7 days
79
How long to hold Prasugrel before regional anesthesia?
7-10 days
80
How long to hold Ticlopidine before regional block?
10 days
81
How long to hold low dose heparin (<5,000u)?
4-6 hours
82
How long to hold high dose heparin (<20,000u daily) prior to regional anesthesia?
12hrs
83
How long to hold therapeutic heparin (>20,000u daily or in pregnant pts) before regional anesthesia?
24hrs
84
What should you obtain prior to central neuraxial block if the patient has been on unfractionated heparin for >4 days?
Platelet count
85
How long to delay neuraxial after prophylactic dose of LMWH?
12hrs
86
How long to delay neuraxial block after therapeutic dose of LMWH?
at least 24hrs
87
Which patients would you consider checking anti-factor 10a?
Elderly or renal insufficiency taking LMWH
88
How long to hold warfarin prior to neuraxial anesthesia?
5 days (ensure INR <1.5)
89
What medications are absolute contraindications for neuraxial anesthesia?
Thrombolytic agents (tPA, streptokinase, alteplase, urokinase)→ check with provider?
90
Which AC meds need to be DC at least 72 hours before a regional block?
Direct oral anticoagulants→ Apixaban, Betrixaban, Edoxaban, Rivaroxaban, Dabigatran
*consider checking anti-10a level if <72hrs*
91
Should regional block be postponed if patient is taking herbal therapies such as garlic, ginseng, or ginko?
No, proceed with block as long as not taking other blood thinning drugs
92
What causes postdural puncture headaches?
- Failure of dura puncture site to seal properly once breeched by a needle
- Continuous CSF leak→ reduction in CSF volume causing lower pressure around the brain (brain sags and stretches membranes= headaches)
93
What are symptoms of postdural puncture headache and when do they occur?
- 2-3 days post procedure
- Headache that feels worse when sitting or standing
- Headache felt from forehead to back of head (frontal-occipital)
- Nausea
- Photosensitivity
- Double vision
- Ringing in ears
94
What factors increase risk for PDPH?
- Younger pt
- Female pt
- Pregnant pt
- Cutting tip needle (pencil needle better)
- Large diameter needle
- Using air of LOR with epidural (only use small amount)
- Positioning needle perpendicular to spine long axis
95
Which needles are commonly used for epidural and SAB?
- Epidural: Tuohy needle
- SAB: Quincke (increased diameter= more stiff no bend and goes into patient smoothly
96
What is the treatment for PDPH?
- Bed rest
- NSAIDs
- Caffeine
- Epidural blood patch *primary tx 48 hrs post dural puncture*
- Sphenopalatine ganglion block
97
What are the steps for an epidural blood patch to treat PDPH?
- Injecting pts own blood (10-20mL) into epidural space
- 90% effective
- Blood clots off opening in dura
- Very painful on initial injection
- Can go higher or lower than origional injection (Tubog says lower works better so blood is directed up)
98
What is a sphenopalatine ganglion block?
- Low risk tx alt. for PDPH
- Soak cotton swab with LA (1-2% lidocaine or 0.5% bup)
- Tilt pt head back and insert swab into the nose toward the back throat wall
- Leave for 5-10 min
99
When can paresthesia be a complication from neuraxial anesthesia?
- Higher postop incidence if paresthesia encountered during placement
- Deficit follows area where paresthesia occurred
- Epidural catheter lower risk
- Higher incidence with CSE techniques
- Redirection of needle if paresthesia illicited during placement (stop and make sure midline)
- DOCUMENTATION
- Moving pt can increase risk
100
What are indicators of a failed spinal?
- No anesthesia effect after 15-20min→ may need to redo block
- Patchy block→ avoid repeating (neurotoxicity) consider IV sedation of GETA
- Unilateral block→ Adjust position if still not working consider IV sedation or GETA
101
How can post-spinal bacterial meningitis occur?
- Aseptic technique failure
- Scrape dried betadine on area where you introduce needle w/4x4
- Bacteria in blood
102
What is a common bacteria involved with post-spinal bacterial meningitis?
Streptococcus viridans→ found in mouth and hand (wearing mask and washing hands essential to prevent spread)
103
What is the best skin prep for spinal anesthesia according to Miller?
Alcohol and CHG (highly effective in preventing bacterial meningitis)
104
Which nerves are affected in cauda equina syndrome?
L1-S5 and Coccygeal nerves
105
What is the cause of cauda equina syndrome? What are signs and symptoms?
- Cause: Neurotoxicity from high levels of LA affecting nerve function
- Bowel/bladder dysfunction
- Sensory deficit (loss of feeling in legs/feet)
- Back pain
- Saddle anesthesia
- Sexual dysfunction
- Weakness/paralysis
- Can lead to paraplegia (late sign)
106
What factors increase risk of cauda equina syndrome?
- High concentration local anesthetics (5% lidocaine)
- Microcatheters→ deliver drug on small area and increases nerve damage (multipore better)
- Whiticare 25/26 needles
107
What is the treatment for cauda equina syndrome?
- Supportive care
- If compression is a factors→ immediate laminectomy <6hrs
108
What are causes of transient neurologic symptoms?
- Improper patient positioning during procedure can stretch nerves causing temporary symptoms
- Myofascial strain and spasms
109
What factors increase risk of transient neurologic symptoms?
- Higher incidence when using 5% lidocaine
- Surgical positions (lithotomy, hip/knee flexion)
- Outpt surgeries and knee arthroscopy
110
Signs and symptoms of transient neurological symptoms?
- Pain: Severe radicular pain in back and butt that spreads down both legs
- Timing: pain starts 6-36 hrs postop and lasts 1-7 days
- Resolves within a week (90% cases)
111
What are treatment options for transient neurologic symptoms?
- Pain relief: NSAIDs and opioids
- Trigger point injections: relieve muscle spasms and pain
112
How can you prevent retained catheter fragments when removing and epidural catheter?
Always withdraw the needle and catheter at the same time to prevent catheter from sheering
113
What should you do if there is resistance when you are trying to remove an epidural catheter?
- Position: Same position during insertion or later decub
- Apply gentle continuous pulling
- Tap traction: Tape catheter to skin and gently pull
114
What needs to be done if the epidural catheter break inside the patient?
- Tell the patient
- Monitor for complications
- If neurological symptoms develop may need surgery to remove catheter piece
115
What should you do if you get a decent amount of blood return in your epidural needle?
Needle might be too far lateral→ adjust needle and aim more midline
116
What should you do if you pull blood when trying to use the epidural catheter?
Slightly pull back the catheter and flush with saline→ continue this until no more blood is drawn or if the catheter cant be adjusted further safely
117
What is one way to prevent epidural vein cannulation?
Inject fluid in epidural space before placing catheter (epi)
118
What are risk factors for epidural vein cannulation?
- Multiple attempts (no more than 3)
- Pregnancy (engorged veins)
- Stiff catheters are harder to maneuver and more likely to puncture vein
- Trauma to epidural vein during block
119
How should you position a patient that is only numb on the right side from an epidural? *assuming hyperbaric LA*
Put patient on left side so gravity can help move LA
120
What are common causes of unilateral epidural block?
- Catheter may have been inserted too far→ exiting the epidural space through intervertebral foramen
- Catheter tip might be too close to a nerve
121
What are solutions for unilateral epidural block?
- Adjust catheter: pull 1-2 cm but ensure at least 3cm remains in epidural space
- Reposition patient: Lateral decub with side not facing numb facing down
- Give more anesthetic (dilute anesthetic to try to even out block)
- Catheter placement: if adjustments and additional anesthetic dont resolve the issue the catheter may need to be replaced
