Epidural Analgesia

This administration of epidural analgesia. Placement of an epidural catheter is covered elsewhere.

Overview:

• Provides better analgesia than system opioids, irrespective of patient or surgery type
  Provides ~ 1/10 reduction in pain over the first 24 hours postoperatively.
• Reduces:
  • Respiratory failure
    After major surgery in high risk patients; NNT 15.
  • MI risk.
  • Muscle catabolism and subsequent hyperglycaemia
  • Duration of postoperative ileus post-bowel surgery
  • Need for ventilation in rib fractures
  • Incidence of pneumonia and mortality
• Safe
  • Epidural haematoma is vanishingly rare
    
    • Anticoagulation and coagulopathy are the two most important risk factors
    • Decompression within 8 hours of symptom onset ↑ likelihood of partial or good neurological recovery
  • Epidural abscesses
    Most likely to track from skin: significantly reduced with chlorhexidine-impregnated dressings.
• Complications
  • Those relating to insertion and management of any epidural
  • Hypotension
    • May require HDU monitoring/vasopressors
    • Better corrected with vasopressors than volume
      Vasopressors demonstrated to more likely improve GI blood flow than excessive fluid.

Implementation:

• Can be used as a sole technique
  E.g. epidural top-up for LUSCS.
• Can be used as an adjunct to general anaesthesia
  • May be used for either thoracic or abdominal operations
  • Epidural should be sited depending on surgical site
    • Middle of the surgical incision for low-thoracic epidurals
    • Relatively more cranially (i.e. top half) of the incision for high-thoracic epidurals
      Higher sites of insertion exhibit less cranial spread of epidurally administered LA.
• Use of high concentration (e.g. 0.75% bupivacaine) leads to a rapid onset of sensory and motor blockade
  Motor blockade provides muscle relaxation, ↓ the requirement to administer NMBD.
  • 3-5ml of 0.75% bupivacaine can be used for top-up

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References

1. Schug SA, Palmer GM, Scott DA, Alcock M, Halliwell R, Mott JF; APM:SE Working Group of the Australian and New Zealand College of Anaesthetists and Faculty of Pain Medicine (2020), Acute Pain Management: Scientific Evidence (5th edition), ANZCA & FPM, Melbourne.