title: Cp50 of propofol for laryngeal mask airway insertion using predicted concentrations with and without nitrous oxide.
abstract: This study sought to determine the predicted Cp50 of propofol required for laryngeal mask airway insertion (Cp50LMA) and to investigate whether nitrous oxide reduces these required concentrations. Using target-controlled infusion and incorporating the standard Diprifusor pharmacokinetic model, 46 unpremedicated patients were randomly assigned to one of two groups. The patients received either 40% oxygen in air (control group: n = 23), or 60% nitrous oxide in oxygen (nitrous oxide group: n = 23). The target concentration for each patient was determined using the up and down method. Following equilibration between the predetermined blood and effect site concentrations, had been established for > 10 min, laryngeal mask airway insertion was attempted without neuromuscular relaxants. The data were analysed using a probit analysis to obtain Cp50LMA levels. The values for Cp50LMA were 3.24 micro g.ml-1 in the control group and 1.93 microg.ml-1 in the nitrous oxide group.
mesh_terms: D000293:Adolescent; D000328:Adult; D019162:Anesthetics, Combined / Q000097:blood / Q000494:pharmacology; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000097:blood* / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D013509:Gynecologic Surgical Procedures; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007442:Intubation, Intratracheal / Q000379:methods; D017214:Laryngeal Masks; D016015:Logistic Models; D008875:Middle Aged; D009609:Nitrous Oxide / Q000494:pharmacology*; D015742:Propofol / Q000097:blood* / Q000494:pharmacology
chemical_list: D019162:Anesthetics, Combined; D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D009609:Nitrous Oxide; D015742:Propofol