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
- True
- What are the 4 signs/symptoms of tissue damage/inflammation?
-
Redness
Swelling
Pain
Warmth - What type of pain signal does the inflammatory process generate?
- nociceptive
- 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?
- neuropathic
- 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?
-
-allodynia/hyperalgesia
-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?
-
-X-rays
-MRI
-Nerve conduction velocities
-EMG
-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
-opiods
-NSAIDS/Cox2 inhibitors
-Corticosteroids
-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
-IV
-subcutaneous
-oral transmucosal
-transdermal
-rectal
-neuraxial - What are the opiod sites of action?
-
-supraspinal
-spinal (via neuraxial rte)
-peripheral - 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?
-
corticosteroids
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?
-
-analgesics
-adjuvant analgesics
-injection therapies
-counter-stimulus therapy (i.e. TENS)
-psychological and physical therapy
-spinal cord stimulation
-blocks - 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)