A comparison of pre-emptive sciatic nerve block and post-amputation sciatic nerve block and their effect on the incidence of phantom limb pain post-operatively

INTERVENTION: Pre‐operative placement of sciatic nerve block (30ml of 0.25% bupivacaone) and catheter prior to commencement of below knee amputation. Local anaesthetic (3‐5mL/hour 0.5% Bupivicaine) will continue to be infused continuously via the catheter for five days post‐operatively (i.e. the infusion will continue around the clock). CONDITION: Phantom limb pain PRIMARY OUTCOME: Incidence of phantom limb pain will be assessed with a 12 point questionnaire previously used in a survey study on phantom limb pain (Byrne K. Survey of phantom limb pain, phantm sensation and stump pain in Cambodian and New Zealand amputees. Pain Med 2011 May 12(5):794‐98) ; Severity of Phantom limb pain assessed with a 12 point questionnaire usd in a previous study (as above, Byrne K. Survey of phantom limb pain, phantm sensation and stump pain in Cambodian and New Zealand amputees. Pain Med 2011 May 12(5):794‐98) SECONDARY OUTCOME: Acute pain as assessed using a 11 point numberical rate scale (0 = no pain, 10= worst pain imaginable) Opioid consumption over the 5 days post operatively will be taken from the patients prescription chart and PCA chart. Different opioids will be converted to morphine equivalents by accepted conversion factors. INCLUSION CRITERIA: Patients having a Below Knee Amputation ASA 1 ‐ 4