title: The effect of a bolus dose of intravenous lidocaine on the minimum alveolar concentration of sevoflurane: a prospective, randomized, double-blinded, placebo-controlled trial.
abstract: BACKGROUND
  The anesthetic effect of volatile anesthetics can be quantified by the minimum alveolar concentration (MAC) of the drug that prevents movement in response to a noxious stimulus in 50% of patients. The underlying mechanism regarding how immobilization is achieved by volatile anesthetics is not thoroughly understood, but several drugs affect MAC. In this study, we investigated the effect of a single IV bolus dose of lidocaine on the MAC of sevoflurane in humans.
  
  
  METHODS
  We determined the MAC for sevoflurane using the Dixon "up-and-down" method in 3 groups of patients, aged 30 to 65 years, who underwent elective surgery (30 patients per group). Study medication (placebo, 0.75 mg·kg(-1) lidocaine or 1.5 mg·kg(-1) lidocaine) was administered 3 minutes before skin incision after a 15-minute equilibration period and the response to skin incision was recorded (movement versus no movement).
  
  
  RESULTS
  MAC was 1.86% ± 0.40% in the placebo and 1.87% ± 0.45% in the 0.75 mg·kg(-1) lidocaine group (P = 1.00). MAC was 1.63% ± 0.24% in the 1.5 mg·kg(-1) lidocaine group, which was significantly lower than that of the placebo group (mean difference of 0.23% sevoflurane [95% adjusted confidence interval {CI}, 0.03-0.43]; P = 0.022). No significant difference was observed between the 0.75 mg·kg(-1) lidocaine and the placebo groups (mean difference of -0.01% sevoflurane [95% adjusted CI, -0.27 to 0.25]; P = 1).
  
  
  CONCLUSIONS
  IV 1.5 mg·kg(-1) lidocaine decreased the MAC by at least 0.03% sevoflurane (mean difference 0.23% sevoflurane [95% adjusted CI, 0.03-0.43]). We did not observe a significant reduction in the MAC of sevoflurane with the IV administration of 0.75 mg·kg(-1) lidocaine.
authors.affiliation: Department of Anesthesiology and General Intensive Care Medicine, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria. thomas.hamp@meduniwien.ac.at
authors.forename: Thomas
authors.initials: T
authors.lastname: Hamp
authors.forename: Mario
authors.initials: M
authors.lastname: Krammel
authors.forename: Ulrike
authors.initials: U
authors.lastname: Weber
authors.forename: Rainer
authors.initials: R
authors.lastname: Schmid
authors.forename: Alexandra
authors.initials: A
authors.lastname: Graf
authors.forename: Walter
authors.initials: W
authors.lastname: Plöchl
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000368:Aged; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D001317:Austria; D004311:Double-Blind Method; D017558:Elective Surgical Procedures; D006801:Humans; D007275:Injections, Intravenous; D008012:Lidocaine / Q000008:administration & dosage*; D008738:Methyl Ethers / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008875:Middle Aged; D009043:Motor Activity / Q000187:drug effects; D017288:Pain Threshold / Q000187:drug effects; D011446:Prospective Studies; D011650:Pulmonary Alveoli / Q000187:drug effects* / Q000378:metabolism; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D000779:Anesthetics, Local; D008738:Methyl Ethers; D000077149:Sevoflurane; D008012:Lidocaine