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Abstract

tions, leads one to ask if relatively high concentrations of local anaesthetic should ever be used for postoperative analgesia. Opioids and local anaesthetics have been shown to be synergistic in animal models and at least additive in several human postoperative analgesia trials. 2-4 However, recent reports have shown that an additive analgesic interaction can be attained with relatively low concentrations of bupivacaine (0.1-0.3 mg-m1-1) infused at a rate of 1-5 mg.hr-aJ s-s) It may also be necessary to titrate the local anaesthetic and opioid separately to obtain the greatest degree of analgesic synergy. Fixed mixtures of opioids and local anaesthetics make it difficult to optimize the benefits of each analgesic and reduce side effects, s-s This may be best accomplished by utilizing a patient controlled analgesia delivery system for the opioid component.Kahn's report points out the potential for high concentrations of bupivacaine to produce confusion in the evaluation of postoperative neurological deficits. Concentrations of bupivacaine > 0.06% do not appear to add much in analgesic benefit and contribute to a greater incidence of motor block and hypotension. 3-s I would suggest that any patient developing motor deficit in the postoperative period should have the local anaesthetic discontinued from the epidural analgesic solution. The patient should be reevaluated within two hours to examine for regression of the nerve block. Furthermore, concentrations of bupivacalne > 0.06% are not warranted and should be abandoned in the delivery postoperative epidural analgesia.