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Chapter 4

Chapter 4. Pain. Pain. Unpleasant sensation 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. Causes of Pain. Inflammation

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Chapter 4

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  1. Chapter 4 Pain

  2. Pain • Unpleasant sensation • 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 • 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 • 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 • May occur with acute pain • 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

  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 • 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

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