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A summary of the chapter on Pain: Pathophysiology and Management:

Introduction

  • Pain is a common symptom prompting medical attention.
    • It serves as a signal of disease and helps in diagnosis.
    • Pain involves both sensation and emotional components.

Pain Sensory System

    • The system detects, localizes, and identifies tissue-damaging processes.
    • Primary afferent nociceptors are responsible for pain detection.
    • Pain signals are transmitted via A-delta (AΞ΄) and C fibers.

Peripheral Mechanisms

    • Sensitization lowers the threshold for nociceptor activation.
    • Leads to increased pain response (hyperalgesia).
    • Inflammatory mediators contribute to sensitization.
    • Nociceptor-induced inflammation can further exacerbate pain.

Central Mechanisms

    • Pain signals enter the spinal cord and are transmitted to the brain.
    • Referred pain occurs due to convergence of nerve fibers in the spinal cord.
    • Ascending pathways, like the spinothalamic tract, carry pain signals to the thalamus and cortex.
    • Pain modulation involves descending pathways that can amplify or inhibit pain. - Psychological factors can influence pain perception.

  • Neuropathic Pain

      • Results from damage to the peripheral or central nervous system.
      • Characterized by burning, tingling, or shock-like sensations.
      • Can occur spontaneously or be triggered by light touch.
      • Sympathetically maintained pain (Complex Regional Pain Syndrome) involves the sympathetic nervous system.

  • Treatment of Acute Pain

    • Non-opioid analgesics: - Aspirin, acetaminophen, and NSAIDs are effective for mild to moderate pain.
    • NSAIDs inhibit cyclooxygenase (COX) enzymes to reduce inflammation.
    • Opioid analgesics:
    • Used for severe pain.
    • Act on the central nervous system to inhibit pain pathways. - Side effects include nausea, sedation, and respiratory depression. - Patient-Controlled Analgesia (PCA): -
  • Allows patients to self-administer predetermined doses of pain medication.

  • Chronic Pain

    • May persist even after the initial injury heals.
    • Requires a comprehensive approach addressing physical and psychological aspects.
    • Assessment should include evaluation of mood, sleep, and daily activities.

  • Treatment of Chronic Pain

    • Antidepressants: - Tricyclic antidepressants (e.g., nortriptyline) can relieve certain types of pain.
    • Anticonvulsants: - Medications like gabapentin are effective for neuropathic pain.
    • Cannabinoids: - May reduce pain intensity and nausea in some patients.
    • Chronic Opioid Therapy: - Used cautiously due to risks of tolerance and dependence. - Requires careful monitoring and adherence to guidelines.
    • Non-Pharmacological Therapies: - Physical therapy, psychological counseling, and nerve blocks. - Minimally invasive procedures like spinal cord stimulation may be considered.

  • Further Reading

    • Studies on pharmacotherapy for neuropathic pain.
    • Guidelines for prescribing opioids for chronic pain.
    • Research on new analgesic agents targeting specific pain pathways.