Pain Definition

An unpleasant sensory and emotional experience associated with actual or potential tissue damage.  A sensation in which a person experiences discomfort, distress, or suffering due to provocation of sensory nerves.

SUBJECTIVE MEASURE

Acute Pain

follows injury to the body and generally disapperas when the bodily injury heals.  It has well defined temporal onset and is often associated with physical signs.  Described as mild, moderate, or severe.  It usually responds to drug therapy.

Chronic Pain

Persists beyond the expecting healing time (pain after 6 months-muscle healing usually takes place over 2-3 months) and often cannt be ascribed to the effects of a specific injury.  It may or may not have a well defined onset and frequently does not respond to typical analgesic therapy.  May be associated with personality changes such as fear, anxiety, and depression having a major impact on process and perception of chronic pain.

Subtypes of Chronic Pain

(4)

1. pain that persists beyond normal healing time

2. pain related to chronic disease

3. pain without identifiable organic cause

4. pain that involves both chronic and acute pain associated with cancer 

Nociceptive Pain

Definition

Subtypes (2)

Commensurate with identifiable tissue damage; presumably related to ongoing activation of primary afferent neurons in response to noxious stimuli.

1. Somatic:  well localized, described as sharp, aching, throbbing

2. Visceral: more diffuse, described as gnawing or cramping

Neuropathic Pain

Definition

Subtypes (2)

Pain believed to be sustained by aberrent somatosensory processing in the peripheral or central nervous system.

1. "Central Generator"-deafferentation pain (central pain, phantom pain)/sympathetically-maintained pain (CRPS)

2.  "Peripheral Generator"-originate in the nerve root, plexus, or nerve/polyneuropathies, mononeuropathies 

Idiopathic Pain

Pain, not attributable to identifiable organic or psychologic processes

Psychogenic Pain

Sustained by psychologic factors

Breakthrough pain

Transient pain, severe or excruciating, over baseline of moderate pain

Major Types of Pain/Pain Syndromes

(12)

1. Acute post-op or trauma pain

2. Acute/chronic pain associated with cancer

3. Chronic non-malignant pain

4. Pain from arthritis (OA and RA)

5. Lower back pain secondary to injury

6. Lower back pain secondary to vertebral fracture or compression

7. Headache/Migraine

8. Post-herpetic neuralgia

9. Peripheral Neuropathy

10. Fibromyalgia

11. Dysmennorhea

12. Phantom limb pain

Pathophysiology of Pain

Nerve endings activated in response to tissue injury

Widely distributed throughout the body

Injury tissues release inflammatory substances that activate and sensitive nociceptors

Sensitized nociceptors transmit stimuli more intensely and have more spontaneous activity

Pathophysiology of Pain

Afferent nerve fibers differ in their rates of impulse transmission

A-delta fibers transmit impulses rapidly; well-localized, sharp, stinging pain

C fibers transmit impulses more slowly; generalized, lingering dull aches

A-beta fibers stimulation have inhibitory effect on pain transmission

Ascending and descinding pathways converge in the dorsal horn of the spinal cord; referred pain is possible

Pain Receptors

Opioid Receptors

Endongenous Opioids

(7)

Opioid receptors in the spinal cord and central nervous system impact descending pain signals

Endogenous opioids and monoaminergic substances play important roles in the pain transmission system:

Beta-endophorins, Dynorphins, Enkephalins, Norepinephrine, Serotonin, Glutamate, GABA 

Somatic Pain

Characteristics

Treatment (2)

Constant, well-localized, aching, throbbing

Analgesics

Nerve Blocks (Opioid Sensitive)

Visceral Pain

Characteristics

Treatment (2)

Diffuse, deep, dull, cramping, squeezing, referred

Analgesics

More complex neurological procedures (opioid sensitive)

Neuropathic Pain

Characteristics

Treatment (3)

Altered sensations, stabbing, burning, constant or intermittent

TCAs

Anticonvulsants

Neurosurgical procedures (Opioid Insensitive)