pain

• Pain


  Pathophysiologic phenomena associated with the central and peripheral nervous systems
• Nociceptors


  • Sensory receptors that detect signals from damaged tissue and chemicals released from the damaged tissue
  • Located at the peripheral ends of both myelinated nerve endings of type A fibers and unmyelinated type C fibers
  • Three types: mechanosensitive, temperature-sensitive, and polymodal
• Nociceptors are distributed in the body, skin, subcutaneous tissue, skeletal muscle, joints, peritoneal surfaces, pleural membranes, dura mater, and blood vessel walls, but not in the parenchyma of visceral organs
• Transduction of pain

  1. Noxious stimulus results in tissue injury or damage stimulating the nociceptors

  2. Nociceptors are the primary afferent nerves for receiving painful stimuli

  3. Noxious stimuli initiate an inflammatory process leading to release of cytokines and neuropeptides

  4. Activation of the primary afferent nociceptors (A-delta and C fibers)

  5. Nociceptors release substance P that enhances nociception, causing vasodilation, increased blood flow, and edema
• Transmission of pain

  1. A-delta primary afferent fibers transmit fast pain to the spinal cord within 0.1 seconds

  2. C fibers transmit slow pain within 1 second

  3. Impulse conducted in the primary afferent neurons to the dorsal horn of the spinal cord

  4. Neurotransmitters released and concentrated in the substantia gelatinosa

  5. Output neurons from the dorsal horn cross the anterior white commissure and ascend the spinal cord in the anterolateral quadrant
• There are several tracts within the anterolateral quadrant: spinothalamic, spinoreticular, spinomesencephalic, spinotectal, and spinohypothalamic
• The anterolateral tracts relay sensations of pain, temperature, nondiscriminative (crude) touch, pressure, and some proprioceptive sensation
• Physiologic processes involved in pain perception (or nociception) include transduction, transmission, perception, and modulation
• Pain perception

  1. Emotional status (depression and anxiety) affects directly the level of pain perceived and thus reported by clients

  2. Hypothalamus and limbic system are responsible for the emotional aspect of pain perception

  3. Frontal cortex is responsible for the rational interpretation and response to pain
• Modulation of pain


  Changes or inhibits the pain message relay in the spinal cord
• Modulation of pain

  Descending modular pain pathways either increase (excite) or inhibit pain transmission
• Endogenous neurotransmitters involved with modulating pain

  • Endogenous opioids, such as endorphins and enkephalins
  • Serotonin
  • Norepinephrine (noradrenaline)
  • Gamma-aminobutyric acid (GABA)
  • Neurotensin
  • Acetylcholine
  • Oxytocin
• The process of pain perception is still poorly understood
• Pain

  • Elicits a stress response in the human body
  • Triggers the sympathetic nervous system
  • Results in physiologic responses
• Physiologic responses to pain

  • Anxiety
  • Fear
  • Hopelessness
  • Sleeplessness
  • Thoughts of suicide
• Physiologic responses to pain

  • Focus on pain
  • Reports of pain
  • Cries and moans
  • Frowns
  • Facial grimaces
• Physiologic responses to pain

  • Decrease in cognitive function
  • Mental confusion
  • Altered temperament
  • High somatization
  • Dilated pupils
• Physiologic responses to pain

  • Increased heart rate
  • Increased peripheral, systemic, and coronary vascular resistance
  • Increased blood pressure
• Physiologic responses to pain

  • Increased respiratory rate
  • Sputum retention
  • Infection
  • Atelectasis
• Physiologic responses to pain

  • Decreased gastric and intestinal motility
• Physiologic responses to pain

  • Decreased urinary output
  • Urinary retention
  • Fluid overload
  • Depression of all immune responses
• Physiologic responses to pain

  • Increased antidiuretic hormone
  • Increased epinephrine
  • Increased norepinephrine
  • Increased aldosterone
  • Increased glucagons
  • Decreased insulin
  • Decreased testosterone
• Physiologic responses to pain

  • Hyperglycemia
  • Glucose intolerance
  • Insulin resistance
  • Protein catabolism
• Physiologic responses to pain

  • Muscle spasm
  • Impaired muscle function
  • Immobility
  • Perspiration
• Psychological pain

  Emotional pain or mental pain; refers to pain originating from the person's psychological dimension and has been found to underlie suicidal behavior
• Psychosomatic or psychogenic pain


  The process of somatization, when psychological pain becomes physical
• Psychosomatic or psychogenic pain


  • Limb paralysis
  • Sensory loss
  • Seizures (often called pseudoseizures)
• Nociceptive pain


  Pain caused by nerve receptors detecting harmful stimuli. The receptors react to mechanical, chemical, or thermal stimuli that may cause damage to skin, muscles, bones, or connective tissue
• Nociceptive pain is the most common type of pain
• Neuropathic pain


  Results from damage or dysfunction of any level of the nervous system (peripheral nerves, spinal cord, or brain)
• About 30% of neuropathies are caused by diabetes
• Inflammatory pain


  Has two aspects: inflammatory and immune responses accompanying and causing both nociceptive and neurologic pain; and inflammatory pain syndromes, such as back pain, shoulder pain, arthritis, rheumatoid arthritis, fibromyalgia, and migraine
• In many types of pain, inflammatory pain is involved and may enhance the sensation of pain
• Somatic pain


  Occurs when stimuli in the tissues (skin, muscles, joints, skeleton, connective tissue) are activated. Stimuli such as force, temperature, vibration, and swelling activate the nerve receptors and produce a sensation of cramping, gnawing, aching, or sharp pain
• Visceral pain


  Occurs when nerves in the internal organs in the chest, abdomen, intestines, or pelvis are stimulated. Visceral pain feels vague, not localized, with a sensation of a deep squeeze, pressure, or aching
• Radicular pain


  Generated by stimuli at the nerve root at its connection to the spinal nerves
• Referred pain


  A sensation of pain in a body region distant from the actual source of the painful stimulus
• Phantom pain


  Pain in a part of the body that has been removed, such as a leg
• Cancer pain


  More than one type of pain. Cancer may have little to no pain. When pain occurs, the first pain is often related to tumor pressure on nerves, bones, or other body organs. Cancer treatments (chemotherapy and radiation) also cause their own pain responses. Cancer pain may be acute or chronic. Types of pain in cancer include nerve pain, bone pain, tissue pain, and the pain may be referred or phantom
• Classification Categories for Pain

  • Duration (Acute vs Chronic)
  • Location (Central vs Peripheral)