4 - Chronic Pain Flashcards
What is a phenotypic switch?
Although acute noxious stimuli are transmitted to the spinal cord via Aδ and C fibers, the presence of allodynia is thought to be mediated by the activation of large-diameter Aβ fibers
AB fibers develop the ability to secrete substance P
What causes radicular spinal pathology?
Facet pathology?
mechanical nerve root compression by a herniated disc
degenerative changes to the joints (like arthritis)
What is the treatment for radiculopathy?
Often ESI
What is the treatment for facet pain?
Radiofrequency rhizotomy of the medial branches
Which nerves are most commonly effected by herpetic neuralgia?
Cervical
Thoracic
Trigeminal
What are the two metabolites of morphine?
Morphine - 6 - gluconuride (analgesic)
Morphine - 3 - gluconuride (harmful)
What is NNT?
Numbers Needed to Treat
Why should oxycodone not be taken with alcohol?
Increases its plasma concentration by 300%
What are the weak opiods?
codeine
tramadol
hydrocodone
tapentadol
For what age group is codeine not effective?
Children under 12 lack the enzymes to convert prodrugs to morphine
Get all the side effects but no analgesia
Why are anticonvulsants useful in treating chronic pain?
Block membrane activity (usually via sodium channel blocking)
How long does it take for lidocaine patches to be effective?
A couple of days
What is chronic pain?
Persistent pain with distinct periods of uninterrupted pain for 3 months
Increases in substance P and substance P receptors is specifically related to what kind of pain?
Inflammatory
What are three big differences between inflammatory and neuropathic pain
- Inflammatory pain gets better when inflammation decreases. Neuropathic pain is persistent, even when tissue healing is evident.
- neuropathic pain causes allodynia, inflammatory does not
- neuropathic pain is not adequately managed with NSAIDs
What is CPSP?
Chronic Postsurgical Pain
persistent pain more than 2 months postop that can’t be explained by other causes
The most common surgical procedures assocaited with CPSP are:
thoracic:
mastectomy, thoracotomy, chole, sternotomy etc
AND amputations
AND inguinal surgeries
Which factors predict a LOW likelihood of CPSP?
Young age
Immunosuppression
What is the first line treatment for CPSP?
Antidepressants
What is windup?
Chronic discharge of neurons that leads to overwhelming of the inhibitory systems of neuropathways
What happens when pathologic chronic pain causes displacement of magnesium?
- NMDA receptors are activated
- Calcium ions enter cells, causing exaggerated release of sub P and excitatory AAs
Placebo analgesia is actually ______
a neurochemical event
Why is tylenol lumped in with NSAIDs?
It inhibits COX, but in the brain. It has no impact on systemic inflammation
What are the big ticket side effects from prolonged/excessive NSAID use?
nephrotoxicity
thrombotic events
peptic ulcers
bleeding
What is Acetylsalicylic Acid?
ASA Aspirin is an NSAID
nonselevtive irreversible COX inhibitor
Why is oxycodone highly addictive?
significant kappa receptor activity
Which is more effective in managing pain: SSRIs or SNRIs?
SNRIs
How long is flexeril effective?
Only about four days of use
Baclofen is only indicated:
for extreme spasmodic conditions like cerebral palsy, teatnus, and MS
Withdrawal from baclofen can cause:
respiratory failure, seizures, delirium, hemodynamic changes
What is the most common interventional procedure for back pain?
lumbar epidural injections
What are IESI and TESI?
Interlaminar epidural steroid injection (put the needle through the intervertebral lamina and into the epidural space
transforaminal epidural steroid injection (placing the needle into the neuroforamen of the affected nerve root)
Which is more effect and which is safer and easier: TESI or IESI
TESI better therapeutic outcome
IESI is safer and easier
What are facet joints?
synovial joints between the lateral aspect of each vertebrae that help to limit movement and resist excessive force on the spine
How is facet joint pain diagnosed?
Treated long term?
diagnostic block
radiofrequency ablation
What is the largest joint in the human body?
Sacroiliac
supports the spine and transfers weight off the pelvis and spine
What has been shown to decrease pain in infants?
smell of amniotic fluid, mother’s milk, baby oil
Swaddling, holding, rocking, skin-to-skin, auditory stimuli
What is perceptual dominance?
a person with pain in one knee is more likely to experience chronic back pain that is less intense
intense pain at one location may cause an increase in the threshold of the other location
Myofascial Pain Syndrome
regional pain syndrome associated with injury to muscle/fascia/tendons
includes myositis, fibrositis, myalgia etc
Complex Regional Pain Syndrome is usually associated with _________
limb injury
changes in hair and nail growth, inflammation, redness, temperature, hypersensitivity and allodynia
