Introduction
Systemic administration of lidocaine significantly decreased propofol requirements when compared to patients receiving placebo. Several studies conducted on animals have proved that systemic local anesthetics reduced minimum alveolar concentration (MAC) of inhalational anesthetics. The aim of this investigation is to study the effect of intravenous administration of lidocaine on the minimum alveolar concentration of sevoflurane required to keep BIS between 40 and 60 during maintenance of anesthesia in humans.
Methods
Twenty-eight ASA I–II adults planned to undergo laparoscopic procedures expected to last <2 h under general anesthesia were randomly assigned to 2 groups. After standardized induction of general anesthesia, patients were given IV lidocaine bolus (1.5 mg kg) followed by 2 mg kg h infusion (group L,  = 14) or equal volumes of saline (group C,  = 14). Primary outcome of the study was end-tidal sevoflurane at bispectral index (BIS) values of 40–60. Secondary outcomes included doses of opioids, BIS values, and extubation time.
Results
The median doses of intraoperative fentanyl (range) in group C were similar to group L ( = 0.08). There were no significant differences between the 2 groups regarding BIS at any time point. End-tidal sevoflurane concentrations were significantly higher in group C than in group L at all intraoperative time points ( < 0.05). Extubation time was longer in group L than in group C ( = 0.04).
Conclusion
In conclusion, intravenous lidocaine administration, during maintenance of general anesthesia, can decrease BIS-guided sevoflurane requirements.