The Mechanism Of Epidural Lidocaine Strengthening The Sedative Effects During Propofol General Anesthesia

Background:This study was to discuss the mechanism about that epidural lidocaine blockade (the same dose of lidocaine) intensify the sedative and hypnotic effects of propofol anesthesia.Methods:66patients, undergoing gastric or intestine surgery were randomly enrolled into this study. All patients were randomly assigned to the following four groups: epidural saline control group (Group C, L2-L3, epidural saline, intravenous saline), intravenous lidocaine group (Group IV, L2-L3, saline epidural, intravenous lidocaine), epidural lidocaine group I (Group EL, L2-L3,1.5%lidocaine epidural, intravenous saline) and epidural lidocaine group II (Group ET, T9-T10,1.5%lidocaine epidural, intravenous saline). Mean arterial blood pressure (MAP), heart rate (HR), pulse oximetry (SPO2), bispectral index (BIS), the induction doses of propofol, the estimated effect site concentration of propofol (Ce) and measured plasma concentration of lidocaine or propofol were recorded at different time points.Results:The induction doses of propofol, Ce and measured plasma concentration of propofol (when BIS value reached60) were significantly higher in the control group than those in the other group. In Group IV, the above parameters were significantly higher than those in the Group EL and Group ET. We also found that there were significant differences of the induction dose of propofol (90±11VS108±13, P=0.009), Ce (1.8±0.36VS2.2±0.44, P=0.032), and the measured plasma concentrations of propofol (3.6±0.42VS4.4±0.70, P=0.004) between Group ET and Group EL.Conclusion:We demonstrated that different routes of administration of lidocaine (intravenous and epidural) intensified the sedative and hypnotic effects on induction of propofol general anesthesia. The epidural lidocaine administration was more prominent than intravenous lidocaine administration did and a higher level of epidural blockade more powerfully intensified the effects of sedation during induction of propofol general anesthesia. Sensor deafferentation may play an important role in the reduction of the propofol requirements.