Propofol does not inhibit lidocaine metabolism during epidural anesthesia

Propofol is sometimes used in combination with epidural anesthesia with lidocaine. In this study, we investigated the effect of propofol on the plasma concentration of lidocaine and its principal metabolites during epidural anesthesia with lidocaine. Thirty-two patients were randomly allocated to receive either propofol or sevoflurane anesthesia (n = 16 each). In the propofol group, anesthesia was maintained with a target concentration of propofol of 4 microg/mL. In the sevoflurane group, anesthesia was maintained with 1.5% sevoflurane. Lidocaine was administered epidurally in an initial dose of 5 mg/kg, followed by a continuous infusion at 2.5 mg x kg(-1) x h(-1). Free components of plasma lidocaine and its metabolites-monoethylglycinexylidide (MEGX) and glycinexylidide (GX)-were measured 30, 60, 120, and 180 min after the initiation of continuous epidural injection by using high-performance liquid chromatography. Free lidocaine, MEGX, and GX were separated from 2 mL of plasma by ultrafiltration filter units. Hemodynamic data were similar between groups. The plasma concentrations of free lidocaine were not significantly different between groups. The ratios of free MEGX to free lidocaine and free GX to free MEGX were not different between groups. In conclusion, propofol does not alter the metabolism of epidural lidocaine compared with sevoflurane.