Pain Management Flashcards by Fiona Lair

Definition: Physiologic pain

Normal response to a noxious stimulus producing protective behavioral responses to potential actual tissue damage

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Definition: Acute pain

Sudden onset of pain which may be severe but disappears when stimulus is removed

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Definition: Chronic pain

Pain that lasts several weeks to months and persists beyond the expected healing time

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Definition: Somatic pain

Originates from damage to bone, joint, muscle, or skin; well localized

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Definition: Visceral pain

Originates form internal organs; poorly localized

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Definition: Neuropathic pain

Originates from injury to the peripheral or central nervous system

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Definition: Inflammatory pain

Originates from tissue damage

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Definition: Referred pain

Originates from one part of the body but perceived as occurring in another

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What is the pain pathway?

Transduction- activation of receptors
Transmission- communication of fibers
Modulation- modification by the spinal cord
Perception- conscious recognition of pain

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What do mechanoreceptors respond to?

Stretching, compression, or crushing

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What do thermoreceptors respond to?

Heat and cold

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What do chemoreceptors respond to?

Chemicals- endogenous or exogenous

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What are the two types of peripheral nerves that conduct pain?

A-delta fibers and C fibers

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What kind of transmission do A-delta fibers perform?

Myelinated, fast transmission

Acute, accurately localized, sharp, rapid onset pain

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What kind of transmission do C fibers perform?

Non-myelinated, slow transmission

Chronic, diffuse, dull, burning, aching pain

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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

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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

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What is the primary inhibitory substances in the spinal cord?

GABA

endogenous opioids

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Where does the spinothalamic tract terminate?

In the thalamus and somatosensory cortex

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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?

Reticular formation

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.

True

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

Definition: Allodynia

Pain evoked by a stimulus that does not normally cause pain

Definition: Hyperalgesia

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

Definition: Windup

Summation of painful stimulation in the spinal cord, mediated by C-fibers Contributes of central sensitization

Definition:

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?

Central sensitization

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)

1. Hyperalgesia 2. Allodynia 3. Spontaneous pain 4. Pain memory

Definition: Analgesia

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?

1. Opioids 2. Alpha-2 agonists 3. NSAIDs 4. NMDA antagonists

What drugs effect perception?

1. Opioids 2. Alpha-2 agonists 3. General anesthetics