Low vs. high concentration of levobupivacaine for post-operative epidural analgesia: influence of mode of delivery

Background: Although the use of continuous epidural infusion (CEI) and patient-controlled epidural analgesia (PCEA) has become commonplace in pain management, there is still controversy regarding the relative effects of mass, volume and concentration of the local anaesthetic. This prospective study evaluated the influence of two concentrations of levobupivacaine on the quality of analgesia in two modes of delivery after lower abdominal surgery. Methods: Eighty-two patients were randomly assigned to four groups to receive combined low thoracic epidural analgesia and general anaesthesia followed by post-operative CEI or PCEA using 1.5 or 5 mg/ml levobupivacaine (15 mg/h in CEI and bolus 5 mg, lockout 20 min in PCEA). Sensory block, pain scores, levobupivacaine and rescue morphine consumption, motor blockade, haemodynamics, side-effects and patient satisfaction were registered within 48 h. Results: The four groups were similar with regard to demographics, quality of analgesia, morphine consumption and satisfaction rate. No difference in the quality of analgesia was observed for the two modes of delivery with regard to the concentration of levobupivacaine, but the consumption of the local anaesthetic was higher in the CEI groups. The Bromage scores in the PCEA groups were reduced to zero for all except one patient, whereas eight patients presented scores of one or more in the CEI population. Conclusion: Levobupivacaine in thoracic epidurals provides an equal quality of post-operative analgesia in low and high volume independent of the delivery mode, i.e. CEI or PCEA. This is in accordance with the assumption that the total dose of the local anaesthetic determines the quality of analgesia.