Chapter 4 Pain

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

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

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

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

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

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

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

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

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

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

Pain Pathways (Cont.)

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

Pain Control―Gate Open

Pain Control―Gate Closed

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

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

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

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

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

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

Location of Referred Pain

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

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

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.

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

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

Comparison of Acute and Chronic Pain

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

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

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.

Analgesic Drugs

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

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

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

Anesthetics