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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 (1:1) 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.
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Objective To examine the difference in myocardial protection provided by continuous and intermittent warm blood cardioplegia during coronary artery bypass (CAB) .Methods Thirty ASA Ⅰ-Ⅱ patients undergoing CAB with warm CPB were randomly divided into two groups : (A) continuous warm blood cardioplegia ( n = 15) and (B) intermittent warm blood cardioplegia ( n = 15) . During CPB the body temperature was maintained at 33℃ -34℃ . Arterial blood samples were taken before skin incision (T0) , 1 h after going on CPB (T1 ) and 6h , 24h after coming off CPB (T2, T3 ), for determination of plasma concentration of cardiac troponin T (cTnT) using ELISA method. A small piece of myocardium was obtained from right ventricle (about 1g ) before aortic crass-clamping and after the aortic clamp was removed for determination of myocardial ATP content and ultrastractural examination. Results The demographic data were comparable between the two groups. Plasma cTnT level increased significantly at T1 and T2 as compared with the baseline values (T0) and then returned to normal level at T3 in both groups. The cTnT level was significantly higher in group B than that in group A at T2 (6h after weaning from CPB)The myocardial ATP content decreased significantly after aortic clamp was removed as compared with that before cross-clamping of aorta, but myocardial ATP content in group A was significantly higher than that in group B after release of arotic clamp. Mitochondria score was significantly higher after release of aortic cross-clamp than that before aortic cross-clamping.Conclusion Continuous warm blood cardiaplegia is superior to intermittent warm blood cardioplegia during CPB in terms of myocardial protection.
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Objective To investigate the pharmacokinetics of epidural ropivacaine in patients with liver dysfunction.Methods Twenty patients aged 20-58 yrs weighing 45-73 kg scheduled for upper abdominal surgery under general combined with epidural anesthesia were divided into 2 groups (n = 10 each) : group Ⅰ patients with obstructive jaundice and group Ⅱ patients with normal liver function. Epidural block was performed at T8.9 interspace. 0.75% ropivacaine 2 mg?kg-1 (containing adrenaline 5 ?g?ml-1) was injected into epidural space over 2 min. General anesthesia was induced at 30 min after epidural ropivacaine with ?-hydroxybutyrate 60-80 mg?kg-1, remifentanil 2 ?g?kg-1 and atracurium 0.5 mg?kg-1. The patients were intubated and mechanically ventilated. Anesthesia was maintained with inhalation of N2O:O2 (1:1) and intermittent i. v. boluses of atracurium and remifentanil infusion when needed. Pinprick sensory level, onset of analgesia and degree of motor block (Bromage scale) were assessed. Blood samples were taken from central vein at 0, 10, 20, 30, 45, 60, 90, 120, 150, 180, 240, 360, 480, 720 min after epidural ropivacaine for determination of plasma concentration of ropivacaine (HPLC). Results The two groups were comparable with respect to F/M ratio, age, body weight, duration of operation, intraoperative blood loss and amount of fluid infused. There was no significant difference in onset time and height of sensory block and degree of motor block. The plasma ropivacaine concentration was significantly higher in group Ⅰ (patients with liver dysfunction) than in group Ⅱ during 180-720 min after epidural ropivacaine. The concentration-time curves in the two groups were fitted to two compartment open pharmacokinetic model. The t1/2? was significantly prolonged, AUC0-t was significantly increased, CL and K10 were significantly decreased in group Ⅰ as compared with group Ⅱ. Conclusions Liver dysfunction does not affect the sensory and motor block produced by ropivacaine within 30 min after epidural injection. The metabolism of ropivacaine is significantly slower in patients with liver dysfunction.