Pharmacokinetics of different concentrations of levobupivacaine for lumbar epidural anesthesia / 中华麻醉学杂志

ABSTRACT

Objective To investigate the pharmacokinetics of different concentrations of levobupivacaine for lumbar epidural anesthesia.Methods Twenty ASA Ⅰ or Ⅱ patients of both sexes, aged 35-59 years and scheduled for elective radical resection of rectal or colon carcinoma under general anesthesia combined with epidural block, were randomly divided into 2 groups (n=10 each)group Ⅰ (receiving 0.75% levobupivacaine) and group Ⅱ (receiving 0.5% levobupivacaine). Epidural block was performed at L1-2 interspace. Group Ⅰ and Ⅱ received epidural 0.75% and 0.5% levobupivacaine 2 mg/kg (containing adrenaline 5 μg/kg)injected slowly over 2 min, respectively. And 30 min later, general anesthesia was induced with y-hydroxybutyrate 60-80 mg/kg and remifentanil 1-2μg/kg. Tracheal intubation was facilitated with succinylcholine 1-1.5 mg/kg and the patients were mechanically ventilated. Anesthesia was maintained with inhalation of nitrous oxide (N2 O) and O2 (11) and continuous infusion of remifentanil 0.01-0.1μg·kg-1·min-1 and intermittent intravenous boluses of atracurium. Sensory and motor blocks were assessed after epidural levobupivacaine. Blood samples were taken from the central vein at 0, 10, 20, 30, 45, 60, 90, 120, 210, 300, 420,540, 660 and 840 min, respectively, after epidural administration for determination of plasma concentrations of levobupivacaine by high performance liquid chromatography.Results The plasma concentration-time curves of levobupivacaine were fitted to a two-compartment open model in the two groups and there were no significant differences in the pharmacokinetic profiles between the two groups. The onset time of sensory and motor blocks was shorter and the duration of the two blocks was longer with 0.75% levobupivacaine as compared with 0.5%levobupivacaine. The incidences of nausea and vomiting and hypotension were low and no severe cardiovascular and neurological side-effects developed.Conclusion The pharmacokinetic parameters do not differ significantly between epidural 0.75% and 0.5% levobupivacaine when the total doses are the same. And epidural anesthesia with either 0.75% or 0.5% levobupivacaine is safe.