title: Gender differences between predicted and measured propofol C(P50) for loss of consciousness.
abstract: OBJECTIVE
  To investigate gender differences in the effective dose of 50% for loss of consciousness (C(P50LOC)) for propofol using Diprifusor, the most commonly used target-controlled infusion system.
  
  
  METHODS
  Prospective, randomized, comparative study.
  
  
  METHODS
  University-affiliated hospital.
  
  
  METHODS
  50 ASA physical status I and II patients, aged 20 to 50 years, scheduled for minor surgery.
  
  
  METHODS
  Patients were randomized into two groups of 25 patients each. A target-controlled infusion of propofol (Diprifusor) was maintained at a predetermined target concentration. After a 10-minute steady state, blinded investigators evaluated patients' consciousness using verbal commands. The propofol test concentration was predetermined using a modified version of Dixon's up-and-down method (starting at 2.5 mug/mL; step size of 0.1 microg/mL).
  
  
  METHODS
  Predicted and measured C(P50LOC) values and bispectral index (BIS) were obtained by averaging the crossover midpoint (ie, consciousness to unconsciousness). Those values were analyzed by unpaired t test: P < 0.05 was considered significant.
  
  
  RESULTS
  The predicted C(P50LOC) for men was 2.14 +/- 0.10 microg/mL, which was lower than that for women, 2.55 +/- 0.11 microg/mL (P < 0.0001). No significant difference was found for measured C(P50LOC) in men (2.37 +/- 0.41 microg/mL) and in women (2.30 +/- 0.28 microg/mL) or for BIS measurements.
  
  
  CONCLUSIONS
  Predicted C(P50LOC) by Diprifusor for men tended to be underestimated; that for women tended to be overestimated. Our data support a review of Diprifusor (Astra Zeneca, Osaka, Japan) pharmacokinetic parameters to avoid awareness during operation, particularly for women.
authors.affiliation: Department of Anesthesiology, Saitama Medical Center, Saitama Medical University, Kamoda, Kawagoe, Saitama 350-8550, Japan. kmkodaka@cb3.so-net.ne.jp
authors.forename: Mitsuharu
authors.initials: M
authors.lastname: Kodaka
authors.forename: Toshinari
authors.initials: T
authors.lastname: Suzuki
authors.forename: Akihiko
authors.initials: A
authors.lastname: Maeyama
authors.forename: Kaoru
authors.initials: K
authors.lastname: Koyama
authors.forename: Hideki
authors.initials: H
authors.lastname: Miyao
mesh_terms: D000328:Adult; D000771:Anesthesia, Intravenous / Q000379:methods; D018686:Anesthetics, Intravenous / Q000008:administration & dosage* / Q000493:pharmacokinetics; D001364:Awareness / Q000187:drug effects*; D003243:Consciousness / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006785:Hospitals, University; D006801:Humans; D008297:Male; D008875:Middle Aged; D015742:Propofol / Q000008:administration & dosage* / Q000493:pharmacokinetics; D011446:Prospective Studies; D012737:Sex Factors
chemical_list: D018686:Anesthetics, Intravenous; D015742:Propofol