title: [The relationship between the respiratory parameters under spontaneous breathing and effect site propofol concentrations].
abstract: BACKGROUND
  The prediction of the hypnotic states is useful to maintain the adequate anesthesia. During propofol anesthesia, the respiratory depression has been documented in a dose-dependent manner. Therefore, we investigated whether the respiratory depression under the spontaneous breathing reflected the estimated effect site propofol concentrations (Cp) in a dose-dependent fashion.
  
  
  METHODS
  We enrolled 12 patients for elective lower limb surgery under combined subarachnoid anesthesia and propofol sedation. The respiratory parameters and BIS were measured at the Cp of 5 microg x ml(-1) followed by the 0.5 microg x ml(-1) decrements until the patients' movement. Effective indices to predict patients' movement were determined by receiver-operator characteristics.
  
  
  RESULTS
  The significant correlations within a particular patient between the respiratory parameters and Cp were observed, although those were not between the patients. An EtCO2 of 53 mmHg or greater represents a clinically determinant condition for non-movement of the patients.
  
  
  CONCLUSIONS
  We concluded that the respiratory parameters during spontaneous breathing were useful indices to predict the changes in the effect site propofol concentrations and to maintain the adequate anesthetic levels.
authors.affiliation: Department of Anesthesiology, Ichikawa General Hospital, Tokyo Dental College, Ichikawa 272-0824.
authors.forename: Yoshimune
authors.initials: Y
authors.lastname: Osaka
authors.forename: Toshiya
authors.initials: T
authors.lastname: Koitabashi
mesh_terms: D000328:Adult; D000368:Aged; D000768:Anesthesia, General / Q000379:methods*; D000775:Anesthesia, Spinal; D018686:Anesthetics, Intravenous; D002245:Carbon Dioxide / Q000097:blood; D017558:Elective Surgical Procedures; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015742:Propofol / Q000008:administration & dosage; D012372:ROC Curve; D012119:Respiration / Q000187:drug effects*
chemical_list: D018686:Anesthetics, Intravenous; D002245:Carbon Dioxide; D015742:Propofol