Flashcards in Pain Management Deck (49):
Definition: Physiologic pain
Normal response to a noxious stimulus producing protective behavioral responses to potential actual tissue damage
Definition: Acute pain
Sudden onset of pain which may be severe but disappears when stimulus is removed
Definition: Chronic pain
Pain that lasts several weeks to months and persists beyond the expected healing time
Definition: Somatic pain
Originates from damage to bone, joint, muscle, or skin; well localized
Definition: Visceral pain
Originates form internal organs; poorly localized
Definition: Neuropathic pain
Originates from injury to the peripheral or central nervous system
Definition: Inflammatory pain
Originates from tissue damage
Definition: Referred pain
Originates from one part of the body but perceived as occurring in another
What is the pain pathway?
1. Transduction- activation of receptors
2. Transmission- communication of fibers
3. Modulation- modification by the spinal cord
4. Perception- conscious recognition of pain
What do mechanoreceptors respond to?
Stretching, compression, or crushing
What do thermoreceptors respond to?
Heat and cold
What do chemoreceptors respond to?
Chemicals- endogenous or exogenous
What are the two types of peripheral nerves that conduct pain?
A-delta fibers and C fibers
What kind of transmission do A-delta fibers perform?
Myelinated, fast transmission
Acute, accurately localized, sharp, rapid onset pain
What kind of transmission do C fibers perform?
Non-myelinated, slow transmission
Chronic, diffuse, dull, burning, aching pain
Describe the spinal cord pathway of pain
Afferent fibers (A-delta or C) -->> Spinal cord through dorsal root -->> Synapse in Lamina II in dorsal horn grey matter -->> ascend via spinothalamioc and spinoreticular tracts -->> brain
What is the primary excitatory/facilitory substances in the spinal cord and what are their receptors?
Substace P- NK1 receptor
Glutamate- AMPA, NMDA, kainate receptors
What is the primary inhibitory substances in the spinal cord?
Where does the spinothalamic tract terminate?
In the thalamus and somatosensory cortex
What does the spinothalamic tract transmit?
Easily localized, superficial pain
How is the spinothalamic tract tested?
Brief skin pinch
Where does the spinoreticular tract terminate?
What does the spinoreticular tract transmit?
Deep and visceral pain
How is the spinoreticuclar tract tested?
Hemostats on the toenail bed to stimulate the periosteum
Where is pain information received and inhibitd in the midbrain?
Periaqueductal grey matter
Nucleus raphe magnus
What do the axons in the PAG and NRM release to inhibit pain?
endorphins, serotonin, and NE
T/F: the PAG and NRM are the pharmacologic target for pain control.
What nerve mediates pain in the head?
Trigeminal nerve (CN V)
What are some systemic consequences of unmanaged pain?
Mainly stress response (increased sympathetic tone)
Classic manifestation of stress in all organ systems
Pain evoked by a stimulus that does not normally cause pain
An increased/exaggerated response to a stimulus that is normally painful
Where does primary hyperalgesia occur?
At the site of injury
Where does secondary hyperalgesia occur?
Surrounding undamaged tissues
Definition: Peripheral sensitization
An increase in the activity/excitability and responsiveness of peripheral nerve terminals leading to primary hyperalgesia
Summation of painful stimulation in the spinal cord, mediated by C-fibers
Contributes of central sensitization
An increase in the activity/excitability and responsiveness in the central nerve system (spinal cord) leading to primary and secondary hyperalgesia and allodynia
What is the reason for peripheral sensitization?
Lowered threshold for nociceptive fibers and activation of additional receptors Due to inflammation
Where does windup occur?
Dorsal horn neurons
Which receptors become active in the dorsal horn with windup?
NMDA receptors- available for binding by glutamate to increase pain transmission
What does windup contribute to?
What is central sensitization due to?
Increase in dorsal horn excitability and decrease in inhibition at the spinal cord level (GABA activity)
What does central sensitization result in? (4)
3. Spontaneous pain
4. Pain memory
Loss of sensitivity to pain
Definition: Multimodal analgesia
Use of multiple drugs acting by different mechanisms to produce analgesia
Definition: Preemptive analgesia
Administration of analgesic therapy before painful stimulation; prevents wind up
What drugs block transduction?
1. Topical LAs or cooling
2. Injected LA
3. Systemic NSAIDs
Which drugs block transmission?
LA nerve blockade at peripheral/plexus or eipdural
What drugs block/effect modulation?
2. Alpha-2 agonists
4. NMDA antagonists