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Pain Medicine > Interventional pain > Flashcards

Interventional pain Flashcards

1
Q

MOA for SCS

A

NeP - suppression of central excitation
Ischemic pain - vasodilation and inhibition of sympathetic outflow
Inhibits dorsal horn WDR neuron excitability
increases release of GABA
decreases glutamate release
Increases 5-HT, NE and adenosine in dorsal horn
activation of supraspinal pathway

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2
Q

Patient selection for SCS - appropriate patients must have:

A

diagnosis amenable to treatment with SCS
failed conservative therapy for at least 6 months
all significant psychological issues have been ruled out
no history of illicit drug use
trial has demonstrated pain relief
No systemic infection
Cognitively intact and can engage actively in care

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3
Q

How SCS is actually done

A

placement of platinum alloy electrodes into the posterior epidural space to electrically stimulate the dorsal columns of the spinal cord

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4
Q

Complications of SCS

A 
lack of paresthesia coverage
paralysis
nerve injury
death
complication rate: 28-42%
Most common complication - lead migration or breakage (22%)
superficial infection rates - 2.5-7.5%
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5
Q 
Placement of electrodes in SCS and body targets
C2
C2-4
T5-6
T7-9
T10-10
T12-L1
L1
A 
C2 - lower half of face
C2-4 - neck, shoulder and hand
T5-6 - abdomen
T7-9 - back
T10-10 - leg 
T12-L1 - foot
L1 - pelvis
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6
Q

Name the three types of SCS

A

Traditional - paresthesia overlaps with pain area resulting in decreased pain
High frequency - paresthesia free
Burst - superior pain control as well as axial back pain relief; unique waveform and minimal paresthesia

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7
Q

Conditions that have evidence for SCS?

A 
FBSS
Chronic radicular pain
CRPS
Extremity neuropathic pain
PDN
Peripheral ischemia (Raynauds)
intractable angina
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8
Q

What areas of the spine have the most challenges for SCS lead placement?

A

cervical spine due to high mobility of the mid to lower C-spine.
Thoracic spine is more fixed allowing for less lead migration. But at T5 the spinal cord is thinnest and CSF is largest leading to high stimulation thresholds and postural changes are problematic at this level.

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9
Q

rTMS and tDCS indicated for?

A 
Phantom limb pain
Neuropathic pain (Task Force of European Federation of Neurological Societies deemed rTMS as preliminary or add-on therapies)
SCI pain (tDCS) 3rd line (from CanPain SCI guidelines)
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10
Q

Ketamine infusion indications

A

CRPS (good results in general)
Fibromyalgia (effects lost by 1 week)
Central Neuropathic Pain (decreased pain only during infusions)
Peripheral Neuropathic Pain (pain reduced but only measured to 45min post infusion)
PHN (pain reduced but only measured to 45min post infusion)
Peripheral nerve injury

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11
Q 
Ketamine infusion risks and side effects?
Cardiovascular
Cognitive
Neurological
GI
A

CV - Tachycardia (5-10%), Arrhythmias, hypertension
Cognitive - slurred speech, confusion, sedation, dissociation, euphoria, hallucinations
Neurological - ataxias, paresthesia, headache, diplopia
GI - nausea (5-10% )

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12
Q

Ketamine infusion contraindications?

A

Elevated ICP (?)
Severe CVD
Impaired neurological status

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13
Q

Lidocaine MOA, onset, duration and metabolized by?

A

MOA: Blocks voltage gated Na+ channels and therby blocking depolarization and action potential propagation
Onset 45-90sec
Duration: 10-20min
Hepatically metabolized

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14
Q

How does lidocaine infusions work?

A

Peripheral mechanisms: Blocks ectopic discharge without blocking nerve conduction
Spinal mechanisms: Induces depression of C-fiber evoked activity in wide dynamic range neurons
Supraspinal mechanisms: Effects on paralimbic and medial forebrain structures (procaine and post-stroke studies)

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15
Q

Indications for lidocaine infusions? (conditions that there is evidence for)

A 
peripheral nerve injury
central neuropathic pain (post-stroke or SCI)
chronic daily headache
DPN
CRPS
Fibromyalgia
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16
Q

Lidocaine infusion risks?

A 
Common:
Headache
Metallic taste
Numbness/tingling (mouth, extremities)
Dry mouth
Tachycardia
Tremor
Nausea
Insomnia
Allergic reactions
Serious: Arrhythmias, Hemodynamic instability, Seizures
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17
Q

Lidocaine infusion rate?

A

Effective dose range 1.5-5mg/kg over 30-60min is comparable among different neuropathic painful conditions

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18
Q 
What is the maximum permissible dose of radiation per target organ?
whole body?
lens of the eye?
thyroid?
gonads?
extremities
A 
Whole body - 50mSv
lens - 150 mSv
thyroid - 500 mSv
gonads - 500 mSv
extremities - 500 mSv
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19
Q

Magnification of a fluoroscopic image by a factor of 1 increases the radiation amount by what factor? and increasing by 2?

A

1X - 2.25 times.

2X - 4 times

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20
Q

What are the factors that affect radiation exposure to personnel?

A
  1. time/duration of x-ray exposure
  2. distance from the source
  3. protection from radiation
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21
Q

Major sources of radiation from fluoroscopy?

A

Patient or fluoroscopy table (a conduit for scatter radiation)

22
Q

As the distance from the radiation source is doubled, the exposure rate is reduced by how much?

A

25%

23
Q

Lead aprons of 0.25-0.5mm absorb what percentage of scattered radiation?

A

90-95%

24
Q

Name ten measures for minimizing risks from fluoroscopic X-rays

A
  1. doses are greater and accumulates faster in large patients - take precautions
  2. keep tube current low
  3. keep kVp as high as possible
  4. patient should be as far from X-ray tube as possible
  5. Keep image intensifier as close as possible
  6. Don’t overuse magnification
  7. Remove grid when procedures on small patients
  8. Collimate whenever possible
  9. Everyone wear protective wear
  10. Beam time should be minimal as possible
25
Q
  1. What is the only contrast media can use for spinal injections?
A

low-osmolality contrast media (LOCM) Ex. Isovue-M 200 or 300, Omnipaque 180 and 210

26
Q

What patient characteristics put them at higher risk of severe adverse reaction to contrast media

A
  • history of adverse reaction to contrast
  • history of asthma
  • allergic or atopic patients
  • patients with recent MI, unstable arrhythmias
  • renal failure
  • infants
  • elderly
  • metabolic hematologic disorders
27
Q

What can you premedicate patients with who have a history of reactions to contrast?

A

Prednisone - 50mg 13h, 7h, then 1h before the procedure, methylpred 32mg 12h and 2h before,

28
Q

What does the ABC (automatic brightness control) system do?

A

Analyzes the image contrast automatically and adjusts the current, balancing image contrast and patient safety.

29
Q

What is the usual frequency range for ultrasound?

A

1-18MHz

30
Q

Shorter wavelengths of ultrasound result in higher or lower resolution?

A

higher

31
Q

high frequency linear ultrasound transducers use what wavelength and go to what depth?

A

6-18MHz; 6-7cm

32
Q

low frequency linear ultrasound transducers use what wavelength and go to what depth?

A

2-5MHz; up to 12cm

33
Q

What is anisotropy?

A

change in the characteristics of the image as a result of the change of the US probe angle relative to the structure of interest

34
Q

What is reverberation?

A

a smooth structure (pleura) reflects the sound beam back and forth between itself and the probe causing linear echoes to the structure

35
Q

Ultrasound guided interventions listed in Benson?

A 
Cervical MBBs
Cervical SRNB
Lumbar MBBs
SIJ injection
Caudal ESI
Stellate ganglion block
GON 
Suprascapular nerve block
Intercostal nerve block
ilioinguinal and iliohypogastric nerve block
lateral femoral cutaneous nerve block
36
Q

What are the symptoms of a total spinal?

A
  • unexpected rise in anesthesia block
  • numbness and weakness of upper extremities
  • dyspnea
  • bradycardia
  • hypotension
  • loss of consciousness
  • apnea
  • cardiac arrest
37
Q

What to do for total spinal?

A

Call for help
Call for crash cart
Inform team
If cardiac arrest start CPR, EPI and go to ACLS event
support ventilation and intubate if required
if brady or hypotensive give epi (10-100mcg), if mild brady give atropine (0.5-1mg) but go to epi quickly if needed
give IV fluid blous

38
Q

Signs of anaphylaxis?

A
  • hypoxemia, SOB, tachypnea
  • rash/hives
  • hypotension
  • tachycardia
  • bronchospasm
  • increase in peak inspiratory pressure (PIP)
  • angioedema
39
Q

Treatment of anaphylaxis?

A

Call for help
Call for crash cart
inform team
If pulseless - CPR, EPI 1mg IV boluses and large volume IVF
D/C potential allergens
Give 100% oxygen
IVF blous
EPI IV in escalating doses q2min, start early epi infusion
consider other causes (4Hs and 4Ts)
consider vasopressin or NE infusion
if signs of angioedema - intubate
consider additional IV access and art line
When stable - consider diphemhydramine, ranitidine and methylpred

40
Q

Signs of LAST?

A
  • Tinnitis
  • perioral numbness
  • Metallic taste
  • Slurred speech
  • Sedation
  • Nystagmus
  • Seizure
  • hypotension
  • bradycardia
  • Cardiovascular collapse
  • coma
41
Q

What to do if LAST?

A

Call for help
Call for crash cart
Inform team
Alert possible CPB
If pulseless, start CPR and give <1mcg/kg EPI
Stop LA
Establish airway - ensure adequate ventilation and oxygenation - consider ETT
if seizure - benzos
If signs persist - Intralipid - 1.5mL/kg bolus of 20% intralipid (70kg adult gets 105mL). May repeat loading dose 3X. Consider infusion if persistent symptoms
Ensure monitoring
Treat hypotension
If arrhythmia - go to appropriate ACLS protocol - avoid vasopressin, CCBs, beta-blockers, and LA
Admit to ICU

42
Q

What to do if loss of airway???

A
  1. Call for help
  2. Call for difficult airway cart
  3. Attempt bag-mask ventilation with jaw thrust
  4. Place oral or nasal airway and switch to two-handed mask ventilation
  5. Place LMA if feasible
  6. If need to intubate with ET tube
    - BURP
    - use bougie introducer
    - if DL fails twice, use Video assisted larygnoscopy
    - before VAL, bag-mask again and ventilate
    - optimize patient positioning and blade selection
  7. if all else fails - call for surgical help to perform cricothyrotomy
43
Q

What to do with vasovagal syncope?

A 
Call for help
Call for crash cart
Inform team
Get monitors in place
????
44
Q

What is rTMS?

A

repetitive transcranial magnetic stimulation. uses a magnetic coil to cause a directed electrical current to a specific part of the brain to stimulate neural pathways. In pain you want to target contralateral M1 area.

45
Q

What do you use Dexmedetomidine/Precedex for?

A

sedation, analgesia and anxyiolytic.

Half-life is 2hr

46
Q

MOA of Dexmedetomidine/Precedex?

A

presynpatic activation of alpha-2 presynpactic autoreceptors. Thought to provide analgesia through decreased release of NE
Supraspinal at LC, spinally at the substantia gelatinosus

47
Q

MOA Cryogenic nerve injury

A

Damage to vasa nervorum –> endoneural edema, and consequent axonal degeneration
Autoimmune response - implicated in LT effects of cryoablation

48
Q

Indications for Cryoneurolysis

A

Post-thoracotomy pain, costochondritis, PHN, rib #

Trigeminal neuralgia, atypical facial pain, lumbar facet, MBB

49
Q

Reasons for Cryoneurolysis over RF

A

Not associated w/ neuroma formation, hyperalgesia, and deafferentation pain

50
Q

Temperatures used in CRF vs Pulsed RF

A

65-90 degrees C (CRF) vs. pulsed RF (<42 deg C), but higher voltages to maximize electrical currents

51
Q

Indications for pulsed RF vs CRF

A

PRF - conisdered when furthe rinjury to nerves should be avoided in pts predispoed to NeP vs CRF (ablation) - for mechanical pain (facet jt, SIJ, knee OA)

52
Q

PRF used in?

A

Applied to any peripheral nerve issues (Suprascpular nerves, intercostal nerves post sx tsp pain, LFCN, splanchnic nerve
Multiple pain syndromes (Radicular pain, herniated disc, PHN, post amp stump pain, occipital nerualgia, inguinal herniorrhagphy pain)

Pain Medicine (14 decks)

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