Pharmacokinetics and pharmacokinetics of epidural ropivacaine in patients with liver dysfunction / 中华麻醉学杂志

ABSTRACT

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 N2OO2 (11) 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.