Continuous lumbar epidural infusion of levobupivacaine: effects of small-or large-volume regimen of infusion.

BACKGROUND: The question of whether the dose, concentration or volume of a local anesthetic solution is the relevant determinant of the spread and quality of post-operative epidural analgesia is still open. In this prospective, randomized, double-blind study, we compared the effects of a large volume-low concentration with a small-volume-high-concentration lumbar epidural infusion of levobupivacaine. METHODS: Seventy patients scheduled for total hip replacement were enrolled. After surgery, patients were randomly allocated to receive a continuous epidural infusion of levobupivacaine (10.5 mg/h) using either 0.125\% levobupivacaine infused at 8.4 ml/h (low concentration group, n=35) or 0.75\% levobupivacaine infused at 1.4 ml/h (high concentration group, n=35). We blindly recorded the degree of pain relief at rest and during movement every 8 h for the first two post-operative days, as well as hip flexion, motor block, rescue analgesic consumption and adverse events. RESULTS: No difference in pain relief was observed between groups as estimated with the areas under the curve of the verbal Numerical Rating Scale for pain over time, both at rest and during movement. Similarly, there was no difference between groups in hip flexion degree, motor blockade and hemodynamic stability. CONCLUSIONS: Continuous lumbar epidural infusion of 0.75\% levobupivacaine was as effective as continuous lumbar epidural infusion of 0.125\% levobupivacaine, when administered at the same hourly dose of 10.5 mg, in achieving adequate analgesia both at rest and during movement, without differences in the incidence of hypotension and motor blockade.