title: Intravenous lidocaine increases the depth of anaesthesia of propofol for skin incision--a randomised controlled trial.
abstract: BACKGROUND
  The anaesthetic potency of intravenous propofol is quantified by its Cp50 value, which is defined as the plasma concentration required to prevent movement response in 50% of patients to surgical stimuli. We hypothesised that, in addition to propofol anaesthesia, an intravenous bolus of lidocaine 1.5 mg/kg will decrease the Cp50 value of propofol during anaesthesia.
  
  
  METHODS
  We enrolled 54 elective surgical patients undergoing propofol-based anaesthesia, and randomised them to either lidocaine 1.5 mg/kg, lidocaine 0.5 mg/kg or placebo (NaCl 0.9%) 3 min before skin incision. The propofol Cp50 value was then calculated using the 'up-and-down' method of Dixon and Massey.
  
  
  RESULTS
  There was no significant reduction in propofol requirements after the administration of 0.5 mg/kg lidocaine from 8.5 μg/ml [confidence interval (CI) 6.0-11.625] to 8.25 μg/ml (CI 6.75-9.76); however, a bolus of 1.5 mg/kg lidocaine decreased the Cp50 value of propofol by 42% from 8.5 μg/ml (CI 6.0-11.625) to 4.92 μg/ml (CI 4.5-5.78) (P < 0.05).
  
  
  CONCLUSIONS
  An intravenous bolus injection of 1.5 mg/kg lidocaine 2% caused a significant reduction of the propofol Cp50 value.
authors.affiliation: Department of Anesthesiology, General Intensive Care and Pain Control, Medical University of Vienna, Vienna, Austria.
authors.forename: U
authors.initials: U
authors.lastname: Weber
authors.forename: M
authors.initials: M
authors.lastname: Krammel
authors.forename: S
authors.initials: S
authors.lastname: Linke
authors.forename: T
authors.initials: T
authors.lastname: Hamp
authors.forename: T
authors.initials: T
authors.lastname: Stimpfl
authors.forename: B
authors.initials: B
authors.lastname: Reiter
authors.forename: W
authors.initials: W
authors.lastname: Plöchl
mesh_terms: D000328:Adult; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000779:Anesthetics, Local / Q000494:pharmacology*; D062109:Dermatologic Surgical Procedures; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004357:Drug Synergism; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D008012:Lidocaine / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D015742:Propofol / Q000494:pharmacology*; D011446:Prospective Studies
chemical_list: D018686:Anesthetics, Intravenous; D000779:Anesthetics, Local; D008012:Lidocaine; D015742:Propofol