Intraspinal and Epidural Analgesia

 

Routes

  1. Subarachnoid Space – intrathecal space or spinal canal
  • medication infuses directly into the subarachnoid space and cerebrospinal fluid
  • pain relived through opioid binding to opioid receptors in the spinal canal 
  1. epidural space (The narrow space between the dura mater and the bony walls of the spinal canal)

 

Use:

  • route used for anesthetic adminstration
  • for opioid adminstration to relive:
  1. chronic pain unrelieved by other methods
  2. post-operative pain

 

Method

  • catheter inserted into the subarachnoid space or the epidural space of the thoracic or lumbar vertebrae

 

Intrathecal or epidural adminstration

  • results in pain relief with fewer side effects, such as sedation than systemic pain relief methods

 

Adverse effects of intraspinal administration

  • spinal headache d/t spinal fluid loss as dura is punctured
  • this is most prevalent in those under 40
  • dura puncture occurs with intrathecal route
  • dura puncture may occur inadvertently in epidural route allowing spinal fluid to seep out od the spinal canal
  • the resultant spinal headache from a epidural needle is increased as it is larger than the intrathecal needle and allows more spinal fluid to escape
  • Respiratory depression – generally peaks at 6-12 hrs post epidural opioid administration
  • may occur earlier or up to the 24hrs post inital injection
  • duration of respiratory depression is dependent on the body lipophilicity for the particular opioid
  • Morphine is hydrophilic with a longer time for peak effectiveness than fentanyl (a lipophilic opioid)

 

Monitoring

  1. Respiratory Depression’
  2. Level of Consciousness/Sedation
  • monitor all pts for 24hrs post first injection, longer with resp status changes or level of consciousness changes
  1. Urinary Retention
  2. pruritus
  3. Nausea
  4. Vomiting
  5. Dizziness
  6. For signs of infection

 

Antidote

  • have opioid antagonist naloxone readily available in case of respiratory depression
  • administer only non-preservative containing medications d/t potential neurotoxic effects

 

Abdominal Sx and Post-op complications use:

  • intrathecal opioids post spinal anesthetic adminstration
  • general inhaled anesthetic in combination with a local epidural anesthetic agent are used

 

Chronic Severe Pain

  • long term intrathecal or epidural catheter analgesic pain management
  • used in cases where pain fails to respond to other treatments or where other methods are accompanied by serious side effects
  • an implantable infusion device or pain pump may be used to deliver medication continuously or in cases with frequent dosing required to manage pain.
  • Implanted infusion devices are able to store medication in their reservoirs for 1-2 months depending on pain relief dose requirements

 

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