Chapter%2028%20Pain

Chapter 28: Pain

Professor Constantino

What Is Pain?

  • Definition:

    • Pain is described as an unpleasant sensory and emotional experience.
    • It can have destructive effects and serves as a warning for potential injury.
    • Pain is recognized as a multidimensional experience.

  • Significance in Healthcare:

    • Pain is the most common reason patients seek medical care.
    • The experience of pain significantly impacts quality of life.
    • For instance, severe back pain can affect:
    • Job performance
    • Engagement in social activities
    • Sexual intimacy
    • Sleep and rest
    • Ability to exercise and perform activities of daily living (ADLs)
    • Various factors can influence the intensity of pain and an individual’s response to it, including:
    • Sleep loss
    • Irritability
    • Cognitive impairment
    • Functional impairment
    • Immobility
    • Pain can be destructive to both the patient and their family.

Classification of Pain

By Origin

  1. Superficial
  2. Visceral
  3. Somatic
  4. Radiating/Referred
  5. Phantom
  6. Psychogenic

Detailed Classification of Pain

Superficial
  • Characteristics:
    • Arises from skin or subcutaneous tissue.
    • Typically results from a superficial injury; can cause significant short-term pain.
    • Common examples: touching a hot object or getting a paper cut.
Visceral
  • Characteristics:
    • Involves stimulation of deep internal pain receptors, mostly in the abdominal cavity, cranium, or thorax.
    • Pain is often poorly localized and is described as tight, pressure-like, or crampy.
    • Quality and extent of pain are important for diagnosis.
    • Examples: menstrual cramps, labor pain, GI infections, bowel disorders, organ cancers.
Somatic
  • Characteristics:
    • Pain originates from ligaments, tendons, nerves, blood vessels, and bones.
    • Deep somatic pain is more localized, often described as achy or tender.
    • Examples: fractures, sprains, arthritis, bone cancer.
Radiating Pain
  • Characteristics:
    • Pain originates at a specific location and extends to other areas.
    • Example: severe sore throat pain may radiate to ears and head; heartburn pain may radiate from the sternum to the upper thorax.
Phantom Pain
  • Characteristics:
    • Pain perceived to originate from an area that has been surgically removed.
    • Patients with amputations may still feel the limb and experience burning, itching, or deep pain in that area.
Psychogenic Pain
  • Characteristics:
    • Pain believed to arise from psychological factors; although no physical cause can be identified, the patient perceives the pain as real.
    • Can be as severe as pain from a physical cause.
Referred Pain
  • Characteristics:
    • Pain occurring in a location distant from the original site of injury.
    • Example: heart attack pain may be felt in the left arm, back, or jaw.

Classification of Pain (continued)

By Cause
  • Nociceptive
  • Neuropathic
By Quality
By Duration
  • Acute
  • Chronic
  • Intractable
Nociceptive Pain
  • Occurs when nociceptors respond to potentially damaging stimuli due to noxious thermal, chemical, or mechanical stimuli.
  • Common causes: trauma, surgery, inflammation.
  • Pain felt in tissues or organs, may include referred pain.
Neuropathic Pain
  • A complex and chronic pain arising when injury affects one or more nerves, resulting in continuous pain signal transmission regardless of painful stimuli.
  • Conditions leading to nerve injury may include poorly controlled diabetes, stroke, tumors, alcoholism, amputation, or viral infection.
  • Often described as nerve pain with no actual tissue damage.

Physiology of Pain

Four Major Processes

  1. Transduction: Activation of nociceptors by stimuli.
  2. Transmission: Conduction of pain signals from the periphery to the spinal cord.
  3. Perception: Recognizing and defining pain in the cerebral cortex.
  4. Modulation: Changing the perception of pain through various mechanisms.

Body Reaction to Pain

Impact of Unrelieved Pain on Body Systems

  1. Endocrine
  2. Cardiovascular
  3. Musculoskeletal
  4. Respiratory
  5. Genitourinary
  6. Gastrointestinal
Respiratory System
  • Patients experiencing pain tend to breathe shallowly to limit thoracic and abdominal movement (known as splinting).
  • This can lead to:
    • Reduced tidal volume (the amount of air exchanged with each breath).
    • Increased inspiratory and expiratory pressures.
    • Complications such as pneumonia, atelectasis, and hypercarbia (retained carbon dioxide leading to respiratory acidosis).
Genitourinary System
  • Unrelieved pain can lead to the excessive release of hormones such as catecholamines, aldosterone, ADH, cortisol, and prostaglandins.
  • Consequences include:
    • Decreased urinary output
    • Urinary retention
    • Fluid overload
    • Hypokalemia (low potassium levels)
    • Hypertension
    • Increased cardiac output.
Gastrointestinal System
  • Pain response leads to increased intestinal secretions and smooth muscle tone, but decreased gastric emptying and motility.
Endocrine System
  • Ongoing pain triggers excessive release of:
    • Adrenocorticotropic hormone
    • Cortisol
    • ADH
    • Growth hormone
    • Catecholamines
    • Glucagon
  • Concurrently, insulin and testosterone levels decrease, leading to:
    • Activation of carbohydrate, protein, and fat catabolism (breakdown), causing hyperglycemia and poor glucose utilization.
    • An inflammatory response, combined with endocrine and metabolic changes, can lead to weight loss