Systemic lidocaine decreases the Bispectral Index in the presence of midazolam, but not its absence

Abstract

Study ObjectiveTo evaluate the effects of intravenous (IV) lidocaine on the Bispectral Index (BIS) in the presence or absence of midazolam. DesignProspective, randomized, double-blinded, placebo-controlled clinical study. SettingOperating room of a university hospital. Patients96 ASA physical status 1, 2, and 3 patients undergoing general anesthesia. InterventionsPatients were assigned to one of 6 treatment groups to receive IV midazolam (0.03 mg/kg) or placebo, followed 5 minutes later by one of three IV preinduction doses of lidocaine: 0.5, 1.0, or 1.5 mg/kg. MeasurementsBIS values were recorded before administration of lidocaine and at 30-second intervals afterwards for three minutes. The primary endpoint was the average BIS level recorded. Main ResultsBaseline BIS values were lower in the midazolam group (94 ± 4 vs. 90 ± 7, P < 0.001). There was no significant decrease in BIS values in the placebo group for any of the three lidocaine doses. However, in the midazolam groups, significant decreases in BIS levels versus baseline values were measured. ConclusionIV lidocaine decreases BIS in the presence of midazolam, suggesting that the effect of lidocaine on BIS is not direct, but rather results from modulation by midazolam.