Adjuncts

Nitrous oxide:

• Has analgesic efficacy in labour
  • ↑ maternal satisfaction
• Neuropathy and bone marrow suppression are rare but potentially serious complications of nitrous oxide use
  Consideration should be given to duration of exposure and supplementation with vitamin B₁₂.

Dexamethasone:

• Reduces post-operative pain, as well as PONV and fatigue
• May cause mild hyperglycaemia
• Prolongs duration of sensory and motor block
  Extent is similar when given in the block as to when given systemically.

Other:

• Avoid withdrawal of benzodiazepines in acute pain
• Calcitonin reduces acute (not chronic) phantom limb pain
• No evidence supporting use of cannabinoids

Ketamine:

• Preventive analgesic effect
• Opioid sparing
• Reduces opioid hyperalgesia
• Does not ↑ ICP or reduce CPP
• Reduces chronic post-surgical pain
• Reduces PONV
  In thoracics.
• May be useful in opioid-resistant pain
• Reduces phantom limb pain

Clonidine:

• Useful in opioid users

α2-delta ligands:

• Probably little effect in most patients, but good in opioid tolerant.
• Avoid using PRN
• Gabapentin and pregabalin are opioid-sparing
• Gabapentin reduces phantom limb pain

Lignocaine:

• Perioperative IV lignocaine reduces:
  • Pain
  • Opioid requirement
  • PONV
  • Ileus duration
  • Hospital stay

Antidepressants:

• TCA and SNRIs are effective analgesics in chronic neuropathic pain and fibromyalgia
• Duloxetine may be effective in chronic low back pain

---

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.