Plasma lidocaine concentrations during epidural blockade with isoflurane or halothane anesthesia.

Because isoflurane maintains hepatic blood flow at higher flows than halothane, we proposed that the elimination of lidocaine would be different between these two volatile anesthetics. The plasma lidocaine concentrations were determined in 14 female patients undergoing epidural blockade plus isoflurane anesthesia and compared with those obtained during halothane anesthesia for lower abdominal surgery. General anesthesia was maintained with isoflurane (0.46% +/- 0.04% [mean +/- SE] inspired, n = 7) or halothane (0.48% +/- 0.05% inspired, n = 7) and 67% nitrous oxide in oxygen. All patients received 2% lidocaine solution, 10 mL as a bolus dose and continuous administration at a rate of 10 mL/h, through the epidural catheter. The plasma lidocaine concentrations over 180 min after the epidural injection in patients receiving isoflurane were similar to those in patients receiving halothane. The results suggest that low inspired concentrations of isoflurane do not reduce plasma lidocaine concentrations in patients during epidural blockade, compared with halothane.