Lecture 71 - Pathophysiology of Pain Flashcards

1
Q

CLASSIFICATION OF PAIN

A

acute: injury, post-operative flare
chronic: pain lasts >3 months - nociceptive (inflammatory), neuropathic, visceral (inflammatory), mixed
Appropriate pain assessment and adequate pain management are considered to be standard of care, with pain being considered the “fifth vital sign”

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2
Q

FUNCTIONS OF PAIN

A

Warning system (avoid injury)
Aid in repair (hypersensitivity)
Can be maladaptive (e.g. irreversible neuropathy)

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3
Q

CHARACTERIZATION OF PAIN

A

Temporal features: Onset, duration, course, pattern
Intensity: Average, least, worst, current pain
Location: Focal, multifocal, generalized, referred, superficial, deep - Opioid induced hyperalgesia (generalized)
Quality: Inflammatory: throbbing, pulsating (inflammatory); Neuropathic: stabbing, shooting, burning, tingling; Visceral: squeezing

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4
Q

CLINICAL PAIN ASSESSMENT

A

Pain scale: Adult and children
Subjective: Abused by drug addicts
Pain is an emotion and impacts mood

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5
Q

Pain Transmission

A

Starts with peripheral stimulus (trauma, damage, inflammation) –> conducted to spinal cord where signal is processed and we get activation of CNS –> signal sent through ascending input to the brain for processing (central effect) –> info sent back down through descending modulation back to spinal cord

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6
Q

PERIPHERAL RECEPTORS AND CHANNELS INVOLVED IN PAIN SIGNALING

A

Temperature sensitive: Transient receptor potential cation channel (TRP); TRPV (Vanniloid) = Heat; TRPM (Melastatin) = cold
Acid sensitive: Acid sensing ion channel (ASIC) - Activated by H+, Conduct Na+
Chemical irritant sensitive: Histamine; Bradykinin

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7
Q

REFLEX UPON PAINFUL STIMULI

A

bypasses CNS, goes right back to muscle; signal doesn’t need to go to brain for processing
afferent nerve carries signal into spinal cord, sent to the muscle so body can move from source of pain

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8
Q

NERVE TRANSMISSION FROM PERIPHERY TO THE SPINAL CORD INVOLVES MANY DIFFERENT ION CHANNELS

A

Na+ channels important for conduction of pain signals along axon; conduct the action potential

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9
Q

THREE DIFFERENT PAIN FIBERS TRANSDUCE DIFFERENT PAIN SIGNALS

A

Abeta fibers
adelta fibers
C fibers

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10
Q

Abeta fibers

A

§ Non-noxious: Touch, pressure
§ Innervate the skin
§ Faster, (35-75 m/s)

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11
Q

Adelta fibers

A

§ Pain, cold
§ Myelinated
§ Fast (2-35 m/s)
§ “First pain”, reflex arc - Sharp, prickly

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12
Q

C-fibers

A

§ Pain, Temp, Touch, pressure, Itch (polymodal)
§ Unmyelinated
§ Slow (0.5-2 m/s)
§ “Second pain” - dull, aching

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13
Q

PERIPHERAL SENSITIZATION – SUBSTANCE P PLAYS AN IMPORTANT ROLE IN HEIGHTENING PAIN RESPONDING

A

Repeated stimuli reduces firing threshold; allows area to have more heightened pain response
Substance P
1. Vasodilation
2. Degranulation of mast cells
3. Release of histamine
4. Inflammation and prostaglandins
Increase expression of pain receptors - Sensitization

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14
Q

NEUROPATHIC PAIN SENSITIZATION

A

Possibly enhanced expression of sodium channel subtypes contributing to
* enhanced cellular excitability
* generation of ectopic action potentials
Increased AMPA and NMDA Expression and sensitivity

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15
Q

High expression of _____ receptors in the brain stem along the descending pathway

A

opioid

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