Pathophysiology Chapter 13 Pain - Georgetown ISD



Pathophysiology Chapter 13 Pain

I. Causes of Pain

A. Defense Mechanism

B. Warning of a problem

C. Causes

1. inflammation

2. infection

3. ischemia

4. tissue necrosis

5. stretching of tissue

6. chemicals

7. burns

D. Somatic pain

1. skin or deeper structures (bones, muscles,etc.)

2. conducted by sensory nerves

E. Visceral pain

1. organs

2. conducted by sympathetic nerves

II. Pain Pathways

A. Nociceptors - pain receptors

1. free sensory nerve endings

2. stimulated by thermal, chemical, physical means

B. Pain threshold

1. level of stimulus needed to activate nerve endings enough to perceive pain

2. afferent fibers conduct pain impulses

a. myelinated A delta fibers - transmit rapidly

b. unmyelinated C fibers - transmit slowly

3. acute sharp localized pain - myelintaed A delta fibers

4. chronic pain, dull aching burning sensation - unmyelinated C fibers

C. Dermatome

1. area of skin innervated by each spinal nerve - mapped

2. used to test for sensory loss/sensation

D. Reflex response

1. sudden pain - motor (efferent) impulse results - moves body away from source of pain - involuntary reaction

2. pathway

a. stimulus

b. nociceptor

c. peripheral nerve - afferent pain fiber

d. impulse reaches synapse in spinal cord

e. impulse transmitted to ascending spinal tracts to brain

- 2 types of tracts in spinothalamic bundle: neospinothalamic - fast impulses

paleospinothalamic - slow

f. tracts connect with reticular formation in brainstem (pons, medulla, midbrain,

reticular formation) and thalamus, hypothalamus, etc.

g. ascend to somatic sensory area in cerebral cortex of parietal lobe of brain

h. location and characteristics of pain perceived

i. branches of tracts connect with other parts of brain - give integrated response

j. RAS - reticular activating system - located in pons and medulla

-arousal state influences brain's awareness of incoming pain stimuli

-medications used to depress area/reduce pain

k. response to pain - stress and emotion involved

l. limbic system involved

III. Theory of Pain and Pain Control

A. Control systems (gates) in pain pathways

1. located at nerve synapses in spinal cord/brain

2. open or closed - edit pain moving into spinal cord/brain or response moving from brain/spinal cord

3. factors

a. emotions

b. prior conditioning

c. distractions

d. drugs/alcohol

B. Key to analgesia system

1. opioids secreted by interneuron's within cns (brain/spinal cord)

2. block conduction of pain impulses into cns

3. called endorphins: enkephalins, dynorphins, and beta-lipoproteins

a. attach to opiate receptors on afferent neuron (neuron sending impulse to cns)

b. blocks release of neurotransmitter at synapse

c. prevents transmission of pain stimulus into cns

4. serotonin - increases release of enkephalins

IV. Characteristics of Pain

A. Signs and symptoms

1. pain real sensation but subjective

2. details important in diagnosing severity/cause of pain

a. location

b. adjectives

c. timing of pain

d. association with activity

e. pressure applied at site

f. physical evidence of pain - pallor, sweating, tachycardia, etc.

g. nausea, vomiting, fainting, dizziness

h. anxiety and fear

i. clenched fists/rigid faces; restless/constant motion; guarding affected area

B. Referred pain

1. pain perceived at site distant from source

2. general pain and referred pain characteristic of visceral damage in abdomen

3. characteristics of pain may change with pathology changes

4. example: pain in left neck/arm characteristic of heart attack

5. why - multiple sensory fibers from different areas converge at single level of spinal cord

C. Phantom pain

1. pain/sensation in amputated limb

2. brain thinks limb still present when processing incoming stimuli

D. Factors affecting pain perception and response

1. pain tolerance - degree of pain endured before an individual takes action

2. varies among people and in different situations

3. factors

a. age

b. culture

c. family traditions

d. prior experience

e. personality/temperament

f. circumstances at time of incident

g. fatigue, hunger, presence of other pathologies

V. Acute Pain - see chart - page 233

VI. Chronic Pain - see chart - page 233

VII. Headache

A. Congested sinuses, nasal congestion, eyestrain

1. in eye/forehead area

2. steady/relieved when cause removed

B. Muscle spasm/tension

1. neck muscles contract - pull on scalp

2. dull, constant ache in occipital area

3. last days/weeks

C. headache in temporal area

1. TMJ

2. arthritis

D. Migraine

1. abnormal changes in blood flow and metabolism in brain

2. precipitating factors

a. atmospheric changes

b. stress

c. hunger

d. certain foods/drinks/alcohol/wine

e. menstruation

3. characteristics

a. begin unilaterally in temple area/spread to entire head

b. prodromal period followed by headache

-hallucinations

-aura

-nausea

-skin prickling

c. headache

-visual disturbances

-sensitivity to light and/or sound

-dizziness

-nausea

-fatigue

-abdominal discomfort

d. can last 24 hours or longer

e. some medications "squeeze" blood vessels in brain; others prevent vasodilation

E. Intracranial headaches

1. result from increased pressure inside skull

2. tumors, edema, hemorrhage, infections, inflammation, etc.

VIII. Pain Control

A. Methods of Managing Pain

1. removing cause

2. analgesic medications

3. analgesics classified according to ability to relieve pain

a. mild pain

-acetaminophen (Tylenol) or acetylsalicylic acid (ASA, aspirin)

-act at local site

-aspirin platelet inhibitor

-NSAIDs - naproxen, ibuprofen

-for chronic and acute pain and inflammation

-antipyretic

-this group not effective for severe pain

b. moderate pain

-codeine, percodan, percocet

-alter perception of pain/emotional response

-promotes sense of well being

- dependency

-side effects: nausea, constipation, respiratory depression

c. severe pain

-morphine, hydromorphone

-block pain pathways in cns

-alter perception of pain in positive manner

4. sedatives and antianxiety drugs - lorazepam

-promote rest and relaxation

-reduce dosage required for analgesic

5. chronic and increasing pain

-requires judicious choice of drugs used in step-wise fashion

6. pain management clinics

a. stress reduction/relaxation therapy

b. distracters

c. application of heat and cold

d. massage

e. physiotherapy modalities

f. exercise

g. acupuncture

h. hypnosis

i. imaging

j. therapeutic touch

7. intractable pain

- surgical intervention

B. Anesthesia

1. local

2. general

3. spinal

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