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Clinical Correlation: Pain


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What type of nerve is most important in pain generation?
bare nerve endings
What are the classifications of pain?
anatomic, etiologic, qualitative, and temporal (acute or chronic)
What is chronic pain?
pain that persists longer than it is supposed to or is recurrent; often without precisely defined etiology, time course, or treatment processes
What are the two clinically relevant types of pain?
acute and chronic
What are the two types of chronic pain classification?
nociceptive and neuropathic (pain can be a mixture of the two)
What is nociceptive pain?
pain due to ongoing tissue damage/inflammation
What is neuropathic pain?
pain due to a nervous system injury, in past or ongoing
What pharmocology does nociceptive pain respond to?
traditional analgesics like narcotics and anti-inflammatories
What type of pharmacology does neuropathic pain respond to?
"adjuvant" analgesics such as anti-depressants, anti-convulsants
What type of fibers carry pain information to CNS?
C fibers and poorly myelinated A-delta fibers
T/F: In degenerative joint disease, radiographs that show the joint distruction do not correlate with the amount of pain
What are the 4 signs/symptoms of tissue damage/inflammation?
What type of pain signal does the inflammatory process generate?
What are the effects of inflammation/tissue damage?
nociceptive pain
inc. catecholamines
inc. heart rate
improper stress response (inc. cortisol and other stress hormones)
respiratory effects
autonomic effects (sweating)
psychological effects (aversion and distress)
Is neuropathic pain immediate or delayed?
can be either
What type of pain results when a nerve is cut during surgery?
What are the effects of neuropathic pain?
may have inc. catecholamines
may have dec. cortisol
unreliable respiratory effects
unpredictable autonomic effects
reliable psychological effects
What are the cardinal signs/symptoms of neuropathic pain?
Allodynia and Hyperalgesia
What is allodynia?
pain from stimuli that are not normally painful
What is hyperalgesia?
an exaggerated response to a normally painful stimulus
What are some possible clinical manifestations of neuropathic pain?
-autonomic dysfxn
-trophic changes
-motor impairment
-signs of neural dysfxn
What are the types of neuropathic pain?
1. compressive
2. inflammatory
3. deafferentation
4. Central injury
5. SNS related
What is compressive pain? Is pain immediate or delayed?
active compression on a neural structure; immediate source of pain
What is inflammatory pain?
neuritis can occur when nerves themselves are attacked
What is deafferentation pain?
part of signal is removed, such as with phantom limb pain (i.e. following amputation of a limb)
What causes central injury pain?
a stroke or spinal cord injury
What is SNS related pain?
complex regional pain syndrome; shows up in certain parts of the body every time the SNS fires
T/F: Most neuropathic pain is constant
F: most neuropathic pain is episodic
What are some possible reasons for neuropathic pain?
diabetes, heavy metal exposure, alcohol, vitamin deficiencies, trauma/structural lesions
What do you look at in neurologic examination?
-pain in peripheral nerve distribution
-sensory loss
-motor deficit
-autonomic changes
What are six diagnostic tools to use in a neurologic exam?
-Nerve conduction velocities
-Quantitative sensory testing
-epidermal skin biopsy
What are the limitations of EMG/NCV as diagnostic for neuropathic pain?
-insensitive in acute injury
-normal result does not rule out neuropathic pain
-cannot assess fxn of small fiber nerves involved in most neuropathic pain (C fiber)
What are the ABC's of nerve damage?
Angry Backfiring C-fibers are diseased and causing the pain
How do you treat acute pain?
-assume nociceptive
-traditional analgesics
-treat injury (i.e. broken leg)
What is the pharmacology for nociceptive pain?
-traditional analgesics
-NSAIDS/Cox2 inhibitors
-maybe adjuvants
How do you treat chronic pain?
Start with least invasive (which might not be most efficacious)
psychological physical approaches --> topical meds --> oral meds --> injections --> interventional techniques
What are opiates?
derived from opium related natural compounds
What are the routes of administration of opioids?
-oral transmucosal
What are the opiod sites of action?
-spinal (via neuraxial rte)
What is the benefit of central delivery of opiods?
same efficacy with less side effects (on bowels, bladder, less nausea)
What are important considerations for opiod dosing in chronic pain pts?
-pt will always have pain
-use time-contingent dosing
-goal is improved function
-narcotics can be addictive
-long lasting formulations
-used with metastatic cancer pts
-neuraxial pumps for continuous dosage (only if trouble with oral routes)
Types of anti-inflammatories?
non-specific cyclooxygenase inhibitors
cox-2 inhibitors
Benefits of anti-inflammatories?
less likely to be addictive
oral, parenteral, and injection routes
Limitations of anti-inflammatories?
not as efficacious as narcotics
have toxicities
What are some adjuvant analgesics used in neuropathic pain?
antidepressants, anticonvulsants, anti-arrhythmics, antispastics, alpha-adrenergic agents, topicals
*most were discovered by chance
Neuropathic pain treatments?
-adjuvant analgesics
-injection therapies
-counter-stimulus therapy (i.e. TENS)
-psychological and physical therapy
-spinal cord stimulation
Limitations of using traditional analgesics for neuropathic pain?
rapid development of tolerance
not as efficacious for long term pain
Limitations for using antidepressants for neuropathic pain?
not all are effective for pain (classic such as amitryptyline more effective than newer like prozac)
Limitations for using anti-spastic agents?
side effects (BP, dizziness/balance)

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