1. Chapter 4
Pain

2. Pain Unpleasant sensation Body defense mechanism Complex mechanisms
Discomfort caused by stimulation of pain receptors
Body defense mechanism
Warning of a problem
Complex mechanisms
Many not totally understood
Subjective scales
Developed to compare pain levels over time

3. Causes of Pain Inflammation Infection Ischemia and tissue necrosis
Stretching of tissue
Stretching of tendons, ligaments, joint capsule
Chemicals
Burns
Muscle spasm

4. Somatic Versus Visceral Pain
Somatic pain
From skin (cutaneous)
Bone muscle
Conducted by sensory fibers
Visceral pain
Originates in organs
Conducted by sympathetic fibers
May be acute or chronic

5. Pain Pathways
Nociceptors (pain receptors) are free sensory nerve endings.
May be stimulated by:
Temperature
Extremes of temperature
Chemicals
Examples: acids, bradykinin, histamine, prostaglandin
Physical means
Example: pressure

6. Pain (Cont.) Pain threshold Pain tolerance
Level of stimulation required to elicit a pain response
Usually does not vary among individuals
Pain tolerance
Ability to cope with pain
Culturally related
Varies among individuals

7. Pain Pathways Nociceptors Stimulated by
Thermal means: extreme temperatures
Chemical: For example, acids or chemicals produced by body (e.g., bradykinin, histamine, prostaglandin)
Physical: pressure

8. Pain Fibers Afferent fibers Myelinated A delta fibers
Transmit impulses very rapidly
Acute pain
Sudden, sharp, localized
Unmyelinated C fibers
Transmit impulses slowly
Chronic pain
Diffuse, dull, burning, or aching sensation

9. Pain Pathways (Cont.) Dermatome Reflex response
Area of skin innervated by a specific spinal nerve
Somatosensory cortex → “mapped”
Corresponds to source of pain stimuli
Reflex response
Involuntary muscle contraction away from pain source
Involuntary muscle contraction to guard against movement

10. Pain Pathways (Cont.) Spinothalamic bundle in the spinal cord
Neospinothalamic tract → fast impulses; acute pain
Paleospinothalamic tract → slow impulses; chronic, dull pain
Spinothalamic tracts connect with reticular formation of brain

11. Pain Pathways (Cont.)
Somatic sensory area in the cerebral cortex located in the parietal lobe
Perception and localization of sensation
Hypothalamus and limbic system
Emotional factors
Communication with other regions of the brain to integrate responses
Reticular activating system (RAS)
Reticular formation in the pons and medulla
Awareness of incoming brain stimuli

12. Pain Pathways (Cont.)

13. Physiology of Pain and Pain Control
Gate control theory
Control systems, “gates” built into normal pain pathways
Can modify pain stimuli conduction and transmission in the spinal cord and brain
Gates open
Pain impulses transmitted from periphery to brain
Gates closed
Reduces or modifies the passage of pain impulses

14. Pain Control―Gate Open

15. Pain Control―Gate Closed

16. Pain Control Application of ice
Impulses from temperature receptors close gates.
Transcutaneous electrical nerve stimulation (TENS)
Increases sensory stimulation at site, blocking pain transmission
Opiate-like chemicals (opioids)
Secreted by interneurons of the CNS (endogenous)
Block conduction of pain impulses to the CNS
Resemble morphine
Enkephalins, dynorphins, beta-lipoproteins

17. Signs, Symptoms, and Diagnosis of Pain
Location of pain
Descriptive terms
Aching, burning, sharp, throbbing, widespread, cramping, constant, periodic, unbearable, moderate
Timing of pain
Association with an activity
Physical evidence of pain
Pallor and sweating
High blood pressure, tachycardia

18. Signs, Symptoms, and Diagnosis of Pain (Cont.)
Nausea and vomiting
May occur with acute pain
Fainting and dizziness
Anxiety and fear
Frequently evident in people with chest pain or trauma

19. Signs, Symptoms, and Diagnosis of Pain (Cont.)
Clenched fists or rigid faces
Restlessness or constant motion
Guarding area to prevent stimulation of receptors

20. Young Children and Pain
Infants respond physiologically
Examples: tachycardia, increased blood pressure, facial expressions
Great variations in different developmental stages:
Different coping mechanisms
Range of behavior
Often have difficulty describing the pain
Withdrawal and lack of communication in older children

21. Referred Pain Source may be difficult to determine.
Pain may be perceived at site distant from source
Characteristic of visceral damage in the abdominal organs
Heart attack or ischemia in the heart

22. Location of Referred Pain

23. Phantom Pain Usually in adults
More common if chronic pain has occurred
Can follow an amputation
Pain, itching, tingling
Usually does not respond to common pain therapies
May resolve within weeks to months
Phenomenon not fully understood

24. Pain Perception and Response
Pain tolerance
Degree of pain, intensity, or duration
May be increased by endorphin release
May be reduced because of fatigue or stress
Varies among people in different situations
Pain perception
Subjective but can be compared from day to day in same person
Response to pain
Influenced by personality, emotions, and cultural norms

25. Acute Pain Usually sudden and severe, short term
Indicates tissue damage
May be localized or generalized
Initiates physiologic stress response
↑ Blood pressure and heart rate; cool, pale, moist skin; ↑ respiratory rate; ↑ skeletal muscle tension
Vomiting may occur.
Strong emotional response may occur.

26. Chronic Pain Occurs over extended time; may be recurrent
Usually more difficult to treat than acute pain
Often perceived to be generalized
Individual may be fatigued, irritable, depressed
Sleep disturbances common
Specific cause may be less apparent.
Appetite may be affected.
Can lead to weight gain or loss

27. Chronic Pain (Cont.) Frequently affects daily activities
Accommodation and pacing of activities may be required.
Periods of acute pain may accompany chronic pain conditions.
Usually reduces tolerance to additional pain

28. Comparison of Acute and Chronic Pain

29. Headache: Types and Causes
Congested sinuses, nasal congestion, eye strain
Muscle spasm and tension
From emotional stress
In temporal area
Temporomandibular joint syndrome
Migraine
Abnormal blood flow and metabolism in the brain
Intracranial headaches
Increased pressure inside the skull

30. Headache: Types and Causes (Cont.)
Central pain
Caused by dysfunction or damage to the brain or spinal cord
Neuropathic pain
Caused by trauma or disease involving the peripheral nerves
Ischemic pain
Results from a profound, sudden loss of blood flow to an organ or tissue
Cancer-related pain
Caused by advance of the disease; pain associated with treatment; result of coexisting disease

31. Methods of Managing Pain
Remove cause of pain as soon as possible
Use of analgesic medications
Orally
Parenterally (injection)
Transdermal patch
Classified by ability to relieve
Mild pain
Moderate pain
Severe pain
You may wish to discuss non-pharmacological methods of pain control as well.

32. Analgesic Drugs

33. Methods of Managing Pain (Cont.)
Sedatives and antianxiety drugs
Adjuncts to analgesic therapy
Promote rest and relaxation
May reduce dosage requirements for analgesic
Chronic and increasing pain
May occur in cancer
Stepwise fashion to reduce pain
Tolerance to narcotics develops over time
Increase dose requirements
New drug may be required

34. Methods of Managing Pain (Cont.)
Severe pain
Patients administer medication, as needed.
Patient-controlled analgesia (PCA)
Lessens overall consumption of narcotics
Intractable pain
Cannot be controlled with medication
Surgical intervention is a choice.
Rhizotomy
Cordotomy
Injections

35. Anesthesia Local anesthesia Spinal or regional anesthesia
Injected or applied to skin or mucous membranes
Spinal or regional anesthesia
Blocks pain from legs or abdomen
General anesthesia
Causes loss of consciousness (gas or injection)
Neuroleptanesthesia
Patient can respond to commands.
Relatively unaware of procedure, no discomfort

36. Anesthetics