Effects of age on pharmacodynamics and pahrmacokinetics of levobupivacaine after epidural administration / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effects of age on the pharmacokineties and pharmacodynamics of levobupivacaine after epidural administrstion.Methods Forty-five ASA Ⅰ or Ⅱ patients of both sexes (26 male, 19 female) aged 30-72 yr, weighing 52-83 kg scheduled for elective lower extremity surgery under epidural anesthesia, were divided into 3 age groups ( n = 15 each) group Ⅰ≤45 yr; group Ⅱ 46-64 yr and group Ⅲ > 64 yr. Epidural anesthesia was performed at the L1,2 interspace. All of the patients received levobupivacaine 1.8 mg/kg with epinephrine 5 μg/ml given epidurally over 1.5 min. Assessment of sensory block (onset time, peak effect time, upper spread of sensory block, duration of anesthesia) and degree of motor block (using modified Bromage scale) were made. Blood samples were taken from central vein at 0, 10, 20, 30, 45, 60 90, 120, 240, 360, 480, 840 and 1 440 min after epidural administration for determination of plasma concentration of levobupivacaine by high-performance liquid chromatography (HPLG) in nine patients in each group. The pharmacokinetic parameters were calculated from plasma concentration-time data with 3P97 software package. Results The cephalad spread of sensory block was significantly higher in group Ⅲ than in group Ⅰ . The duration of sensory and motor block was significantly longer in group Ⅲ than in group Ⅰ . The plasma concentration-time curves of levobupivacaine were fitted to a two-compartment open model in the 3 groups. The plasma concentrations of levobupivacaine were significantly higher at 1 440 min after epidural administration in group Ⅲ and Ⅱ than in group Ⅰ. The t1/2β was significantly different among the 3 groups. Conclusion 0.75% levobupivacaine is safe and effective for epidural anesthesia. Age affects the pharmacokinetics (t1/2β in particular) and pharmacodynamics of levobupivacaine administered epidurally.