Interventional pain Flashcards
MOA for SCS
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
Patient selection for SCS - appropriate patients must have:
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
How SCS is actually done
placement of platinum alloy electrodes into the posterior epidural space to electrically stimulate the dorsal columns of the spinal cord
Complications of SCS
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%
Placement of electrodes in SCS and body targets C2 C2-4 T5-6 T7-9 T10-10 T12-L1 L1
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
Name the three types of SCS
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
Conditions that have evidence for SCS?
FBSS Chronic radicular pain CRPS Extremity neuropathic pain PDN Peripheral ischemia (Raynauds) intractable angina
What areas of the spine have the most challenges for SCS lead placement?
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.
rTMS and tDCS indicated for?
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)
Ketamine infusion indications
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
Ketamine infusion risks and side effects? Cardiovascular Cognitive Neurological GI
CV - Tachycardia (5-10%), Arrhythmias, hypertension
Cognitive - slurred speech, confusion, sedation, dissociation, euphoria, hallucinations
Neurological - ataxias, paresthesia, headache, diplopia
GI - nausea (5-10% )
Ketamine infusion contraindications?
Elevated ICP (?)
Severe CVD
Impaired neurological status
Lidocaine MOA, onset, duration and metabolized by?
MOA: Blocks voltage gated Na+ channels and therby blocking depolarization and action potential propagation
Onset 45-90sec
Duration: 10-20min
Hepatically metabolized
How does lidocaine infusions work?
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)
Indications for lidocaine infusions? (conditions that there is evidence for)
peripheral nerve injury central neuropathic pain (post-stroke or SCI) chronic daily headache DPN CRPS Fibromyalgia
Lidocaine infusion risks?
Common: Headache Metallic taste Numbness/tingling (mouth, extremities) Dry mouth Tachycardia Tremor Nausea Insomnia Allergic reactions Serious: Arrhythmias, Hemodynamic instability, Seizures
Lidocaine infusion rate?
Effective dose range 1.5-5mg/kg over 30-60min is comparable among different neuropathic painful conditions
What is the maximum permissible dose of radiation per target organ? whole body? lens of the eye? thyroid? gonads? extremities
Whole body - 50mSv lens - 150 mSv thyroid - 500 mSv gonads - 500 mSv extremities - 500 mSv
Magnification of a fluoroscopic image by a factor of 1 increases the radiation amount by what factor? and increasing by 2?
1X - 2.25 times.
2X - 4 times
What are the factors that affect radiation exposure to personnel?
- time/duration of x-ray exposure
- distance from the source
- protection from radiation
Major sources of radiation from fluoroscopy?
Patient or fluoroscopy table (a conduit for scatter radiation)
As the distance from the radiation source is doubled, the exposure rate is reduced by how much?
25%
Lead aprons of 0.25-0.5mm absorb what percentage of scattered radiation?
90-95%
Name ten measures for minimizing risks from fluoroscopic X-rays
- doses are greater and accumulates faster in large patients - take precautions
- keep tube current low
- keep kVp as high as possible
- patient should be as far from X-ray tube as possible
- Keep image intensifier as close as possible
- Don’t overuse magnification
- Remove grid when procedures on small patients
- Collimate whenever possible
- Everyone wear protective wear
- Beam time should be minimal as possible
- What is the only contrast media can use for spinal injections?
low-osmolality contrast media (LOCM) Ex. Isovue-M 200 or 300, Omnipaque 180 and 210
What patient characteristics put them at higher risk of severe adverse reaction to contrast media
- 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
What can you premedicate patients with who have a history of reactions to contrast?
Prednisone - 50mg 13h, 7h, then 1h before the procedure, methylpred 32mg 12h and 2h before,
What does the ABC (automatic brightness control) system do?
Analyzes the image contrast automatically and adjusts the current, balancing image contrast and patient safety.
What is the usual frequency range for ultrasound?
1-18MHz
Shorter wavelengths of ultrasound result in higher or lower resolution?
higher
high frequency linear ultrasound transducers use what wavelength and go to what depth?
6-18MHz; 6-7cm
low frequency linear ultrasound transducers use what wavelength and go to what depth?
2-5MHz; up to 12cm
What is anisotropy?
change in the characteristics of the image as a result of the change of the US probe angle relative to the structure of interest
What is reverberation?
a smooth structure (pleura) reflects the sound beam back and forth between itself and the probe causing linear echoes to the structure
Ultrasound guided interventions listed in Benson?
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
What are the symptoms of a total spinal?
- unexpected rise in anesthesia block
- numbness and weakness of upper extremities
- dyspnea
- bradycardia
- hypotension
- loss of consciousness
- apnea
- cardiac arrest
What to do for total spinal?
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
Signs of anaphylaxis?
- hypoxemia, SOB, tachypnea
- rash/hives
- hypotension
- tachycardia
- bronchospasm
- increase in peak inspiratory pressure (PIP)
- angioedema
Treatment of anaphylaxis?
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
Signs of LAST?
- Tinnitis
- perioral numbness
- Metallic taste
- Slurred speech
- Sedation
- Nystagmus
- Seizure
- hypotension
- bradycardia
- Cardiovascular collapse
- coma
What to do if LAST?
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
What to do if loss of airway???
- Call for help
- Call for difficult airway cart
- Attempt bag-mask ventilation with jaw thrust
- Place oral or nasal airway and switch to two-handed mask ventilation
- Place LMA if feasible
- 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 - if all else fails - call for surgical help to perform cricothyrotomy
What to do with vasovagal syncope?
Call for help Call for crash cart Inform team Get monitors in place ????
What is rTMS?
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.
What do you use Dexmedetomidine/Precedex for?
sedation, analgesia and anxyiolytic.
Half-life is 2hr
MOA of Dexmedetomidine/Precedex?
presynpatic activation of alpha-2 presynpactic autoreceptors. Thought to provide analgesia through decreased release of NE
Supraspinal at LC, spinally at the substantia gelatinosus
MOA Cryogenic nerve injury
Damage to vasa nervorum –> endoneural edema, and consequent axonal degeneration
Autoimmune response - implicated in LT effects of cryoablation
Indications for Cryoneurolysis
Post-thoracotomy pain, costochondritis, PHN, rib #
Trigeminal neuralgia, atypical facial pain, lumbar facet, MBB
Reasons for Cryoneurolysis over RF
Not associated w/ neuroma formation, hyperalgesia, and deafferentation pain
Temperatures used in CRF vs Pulsed RF
65-90 degrees C (CRF) vs. pulsed RF (<42 deg C), but higher voltages to maximize electrical currents
Indications for pulsed RF vs CRF
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)
PRF used in?
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)
