title: Influence of age and sex on pharmacodynamics of propofol in neurosurgical patients: model development.
abstract: OBJECTIVE
  To determine propofol concentration in the cerebral spinal fluid (CSF) of neurosurgical patients and carry out a preliminary population pharmacodynamic study.
  
  
  METHODS
  Twenty-seven elective neurosurgical patients (12 men and 15 women) aged 17-74 years received propofol in a bolus dose of 2 mg/kg for 5 min and an infusion of 10 mg/kg per h for 5 min. Frequent CSF samples were drawn and assayed for propofol concentration. The bispectral index (BIS) was used to measure the drug effect. All data were analyzed first with the Excel software package, then pharmacodynamics modeling was performed using the NONMEM software package.
  
  
  RESULTS
  The CSF concentration was related to the drug effect with linear and sigmoid Emax models. The parameters for the linear addictive model were a=1.11 and b=95.4. The parameters for the linear exponential model were a=1.05 and b=92.7. The parameters for the sigmoid E(max) model were E(max)=119, EC(50)=53.6 ng/mL, and N=1.51. When the covariates of age, weight and sex were considered, the parameters of models, objective function, the standard error of the mean and the prediction error were not optimized.
  
  
  CONCLUSIONS
  Linear additive, linear exponential and sigmoid E(max) models can be used to describe the pharmacodynamics of propofol with respect to the concentration in CSF. In this small population, age (17-74 years), weight (47-98 kg) and sex did not influence any of the pharmacodynamic parameters of propofol. To verify these preliminary results, a larger study population is required.
authors.affiliation: Department of Anesthesiology, First Affiliated Hospital,Zhejiang University College of Medicine, Hangzhou 310003, China. yuh_li2002@hotmail.com
authors.forename: Yu-Hong
authors.initials: YH
authors.lastname: Li
authors.forename: Fu-Sheng
authors.initials: FS
authors.lastname: Wu
authors.forename: Jian-Guo
authors.initials: JG
authors.lastname: Xu
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D018686:Anesthetics, Intravenous / Q000134:cerebrospinal fluid / Q000493:pharmacokinetics / Q000494:pharmacology*; D001835:Body Weight; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015742:Propofol / Q000134:cerebrospinal fluid / Q000493:pharmacokinetics / Q000494:pharmacology*; D012737:Sex Factors
chemical_list: D018686:Anesthetics, Intravenous; D015742:Propofol