Lesson 10

Pain Management Terminology

  • Allodynia: Pain from a stimulus that does not normally produce pain.
  • Algogenic: A stimulus expected to produce pain.
  • Analgesia: Absence of pain sensation in response to a painful stimulus.
  • Dysesthesia: Abnormal and unpleasant sense of touch.
  • Hyperalgesia: Exaggerated pain response to a painful stimulus.
  • Neuralgia: Pain localized to a dermatome.
  • Neuropathy: Impaired nerve function.
  • Paresthesia: Abnormal pins and needles sensation.

Pain Modulation and Management

  • Pain modulation occurs in the spinal cord.
  • Central sensitization impairs the descending inhibitory pain pathway (mediated by norepinephrine and serotonin).
  • Drugs for Chronic Pain:
    • Tricyclic Antidepressants (TCAs): e.g. Amitriptyline, Nortriptyline.
    • Serotonin/Norepinephrine Reuptake Inhibitors (SNRIs): e.g. Venlafaxine.
    • Selective Serotonin Reuptake Inhibitors (SSRIs): e.g. Duloxetine.
    • Important Side Effects: QT prolongation, orthostatic hypotension, and risk of serotonin syndrome when combining SNRI and SSRI.

Complex Regional Pain Syndrome (CRPS)

  • Types: Type 1 (reflex sympathetic dystrophy), Type 2 (causalgia; always preceded by nerve injury).
  • Risk Factors: Female gender, previous trauma/surgery.
  • Treatment Options:
    • Ketamine infusion
    • Memantine (NMDA antagonist)
    • Gabapentin
    • Regional sympathetic blockade
    • Physical therapy
    • Steroids
    • Amitriptyline

Regional Anesthesia Techniques

  • Thoracic Paravertebral Block:

    • Indications: Breast surgery, thoracotomy, rib fractures.
    • Targets ventral ramus for unilateral sensory and sympathetic block.

  • Celiac Plexus Block:

    • Indications: Cancer pain of the upper abdomen.
    • Complications: Orthostatic hypotension, retroperitoneal hematoma, hematuria, downside of neurolytic).

  • Superior Hypogastric Plexus Block:

    • Indications: Cancer pain of pelvic organs.
    • Risk of injectate migration with neurolytic.

  • Sphenopalatine Block:

    • Used for postdural puncture headache relief.

  • Retrobulbar Block:

    • Unique as optic nerve is enveloped by meningeal sheath.
    • Complications: Blindness (amaurosis) and apnea post-injection; monitor contralateral pupil reflex.