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
