Chapter 4 Pain Pain Unpleasant sensation Body defense
Chapter 4 Pain
Pain Unpleasant sensation Ø Body defense mechanism Ø Warning of a problem Complex mechanisms Ø Discomfort caused by stimulation of pain receptors Many not totally understood Subjective scales Ø Developed to compare pain levels over time • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 2
Causes of Pain Inflammation Infection Ischemia and tissue necrosis Stretching of tissue Stretching of tendons, ligaments, joint capsule Chemicals Burns Muscle spasm • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 3
Somatic Versus Visceral Pain Somatic pain Ø Ø Ø From skin (cutaneous) Bone muscle Conducted by sensory fibers Visceral pain Ø Ø Ø Originates in organs Conducted by sympathetic fibers May be acute or chronic • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 4
Pain Pathways Nociceptors (pain receptors) are free sensory nerve endings. May be stimulated by: Temperature • Extremes of temperature Ø Chemicals • Examples: acids, bradykinin, histamine, prostaglandin Ø Physical means • Example: pressure Ø • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 5
Pain (Cont. ) Pain threshold Level of stimulation required to elicit a pain response Ø Usually does not vary among individuals Ø Pain tolerance Ø Ø Ø Ability to cope with pain Culturally related Varies among individuals • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 6
Pain Pathways Nociceptors Ø Stimulated by • Thermal means: extreme temperatures • Chemical: For example, acids or chemicals produced by body (e. g. , bradykinin, histamine, prostaglandin) • Physical: pressure • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 7
Pain Fibers Afferent fibers Myelinated A delta fibers Ø Ø Transmit impulses very rapidly Acute pain • Sudden, sharp, localized Unmyelinated C fibers Ø Ø Transmit impulses slowly Chronic pain • Diffuse, dull, burning, or aching sensation • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 8
Pain Pathways (Cont. ) Dermatome Ø Ø 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 Ø Involuntary muscle contraction to guard against movement Ø • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 9
Pain Pathways (Cont. ) Spinothalamic bundle in the spinal cord Neospinothalamic tract → fast impulses; acute pain Ø Paleospinothalamic tract → slow impulses; chronic, dull pain Ø Spinothalamic tracts connect with reticular formation of brain Ø • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 10
Pain Pathways (Cont. ) Somatic sensory area in the cerebral cortex located in the parietal lobe Ø Hypothalamus and limbic system Ø Perception and localization of sensation Emotional factors Communication with other regions of the brain to integrate responses Reticular activating system (RAS) Ø Ø Reticular formation in the pons and medulla Awareness of incoming brain stimuli • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 11
Pain Pathways (Cont. ) • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 12
Physiology of Pain and Pain Control Gate control theory Control systems, “gates” built into normal pain pathways Ø Can modify pain stimuli conduction and transmission in the spinal cord and brain Ø Gates open • Pain impulses transmitted from periphery to brain Ø Gates closed • Reduces or modifies the passage of pain impulses Ø • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 13
Pain Control―Gate Open • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 14
Pain Control―Gate Closed • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 15
Pain Control Application of ice Ø Transcutaneous electrical nerve stimulation (TENS) Ø Impulses from temperature receptors close gates. Increases sensory stimulation at site, blocking pain transmission Opiate-like chemicals (opioids) Secreted by interneurons of the CNS (endogenous) Ø Block conduction of pain impulses to the CNS Ø Resemble morphine • Enkephalins, dynorphins, beta-lipoproteins Ø • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 16
Signs, Symptoms, and Diagnosis of Pain Location of pain Descriptive terms Ø Timing of pain Ø Aching, burning, sharp, throbbing, widespread, cramping, constant, periodic, unbearable, moderate Association with an activity Physical evidence of pain Ø Ø Pallor and sweating High blood pressure, tachycardia • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 17
Signs, Symptoms, and Diagnosis of Pain (Cont. ) Nausea and vomiting Ø Fainting and dizziness Ø May occur with acute pain Anxiety and fear Ø Frequently evident in people with chest pain or trauma • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 18
Signs, Symptoms, and Diagnosis of Pain (Cont. ) Clenched fists or rigid faces Restlessness or constant motion Guarding area to prevent stimulation of receptors • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 19
Young Children and Pain Infants respond physiologically Ø Examples: tachycardia, increased blood pressure, facial expressions Great variations in different developmental stages: Ø Ø Different coping mechanisms Range of behavior Often have difficulty describing the pain Withdrawal and lack of communication in older children • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 20
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 Ø Heart attack or ischemia in the heart Ø • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 21
Location of Referred Pain • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 22
Phantom Pain Usually in adults More common if chronic pain has occurred Can follow an amputation Ø Pain, itching, tingling Usually does not respond to common pain therapies May resolve within weeks to months Phenomenon not fully understood • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 23
Pain Perception and Response Pain tolerance Ø Ø Pain perception Ø 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 Subjective but can be compared from day to day in same person Response to pain Ø Influenced by personality, emotions, and cultural norms • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 24
Acute Pain Usually sudden and severe, short term Indicates tissue damage May be localized or generalized Initiates physiologic stress response Ø ↑ Blood pressure and heart rate; cool, pale, moist skin; ↑ respiratory rate; ↑ skeletal muscle tension Vomiting may occur. Strong emotional response may occur. • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 25
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. Ø Can lead to weight gain or loss • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 26
Chronic Pain (Cont. ) Frequently affects daily activities Ø Accommodation and pacing of activities may be required. Periods of acute pain may accompany chronic pain conditions. Usually reduces tolerance to additional pain • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 27
Comparison of Acute and Chronic Pain • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 28
Headache: Types and Causes Congested sinuses, nasal congestion, eye strain Muscle spasm and tension Ø In temporal area Ø Temporomandibular joint syndrome Migraine Ø From emotional stress Abnormal blood flow and metabolism in the brain Intracranial headaches Ø Increased pressure inside the skull • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 29
Headache: Types and Causes (Cont. ) Central pain Ø Neuropathic pain Ø Caused by trauma or disease involving the peripheral nerves Ischemic pain Ø Caused by dysfunction or damage to the brain or spinal cord Results from a profound, sudden loss of blood flow to an organ or tissue Cancer-related pain Ø Caused by advance of the disease; pain associated with treatment; result of coexisting disease • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 30
Methods of Managing Pain Remove cause of pain as soon as possible Use of analgesic medications Ø Ø Orally Parenterally (injection) Transdermal patch Classified by ability to relieve • Mild pain • Moderate pain • Severe pain • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 31
Analgesic Drugs • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 32
Methods of Managing Pain (Cont. ) Sedatives and antianxiety drugs Ø Ø Ø Adjuncts to analgesic therapy Promote rest and relaxation May reduce dosage requirements for analgesic Chronic and increasing pain Ø Ø Ø May occur in cancer Stepwise fashion to reduce pain Tolerance to narcotics develops over time • Increase dose requirements • New drug may be required • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 33
Methods of Managing Pain (Cont. ) Severe pain Ø Ø Ø Patients administer medication, as needed. Patient-controlled analgesia (PCA) Lessens overall consumption of narcotics Intractable pain Ø Ø Cannot be controlled with medication Surgical intervention is a choice. • Rhizotomy • Cordotomy • Injections • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 34
Anesthesia Local anesthesia Ø Spinal or regional anesthesia Ø Blocks pain from legs or abdomen General anesthesia Ø Injected or applied to skin or mucous membranes Causes loss of consciousness (gas or injection) Neuroleptanesthesia Ø Ø Patient can respond to commands. Relatively unaware of procedure, no discomfort • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 35
Anesthetics • Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc. 36
- Slides: 36